draft-ietf-geopriv-rfc3825bis-17.txt   rfc6225.txt 
GEOPRIV Working Group J. Polk Internet Engineering Task Force (IETF) J. Polk
INTERNET-DRAFT M. Linsner Request for Comments: 6225 M. Linsner
Obsoletes: 3825 (if approved) Cisco Systems Obsoletes: 3825 Cisco Systems
Category: Standards Track M. Thomson Category: Standards Track M. Thomson
Expires: August 26, 2011 Andrew Corporation ISSN: 2070-1721 Andrew Corporation
26 February 2011 B. Aboba (ed) B. Aboba, Ed.
Microsoft Corporation Microsoft Corporation
July 2011
Dynamic Host Configuration Protocol Options for Dynamic Host Configuration Protocol Options for
Coordinate-based Location Configuration Information Coordinate-Based Location Configuration Information
draft-ietf-geopriv-rfc3825bis-17.txt
Abstract Abstract
This document specifies Dynamic Host Configuration Protocol Options This document specifies Dynamic Host Configuration Protocol options
(both DHCPv4 and DHCPv6) for the coordinate-based geographic location (both DHCPv4 and DHCPv6) for the coordinate-based geographic location
of the client. The Location Configuration Information (LCI) includes of the client. The Location Configuration Information (LCI) includes
Latitude, Longitude, and Altitude, with resolution or uncertainty Latitude, Longitude, and Altitude, with resolution or uncertainty
indicators for each. Separate parameters indicate the reference indicators for each. Separate parameters indicate the reference
datum for each of these values. This document obsoletes RFC 3825. datum for each of these values. This document obsoletes RFC 3825.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on August 26, 2011. Information about the current status of this document, any errata,
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http://www.rfc-editor.org/info/rfc6225.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction ....................................................3
1.1. Conventions . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Conventions Used in This Document ..........................4
1.2 Resolution and Uncertainty . . . . . . . . . . . . . . . 5 1.2. Resolution and Uncertainty .................................4
2. DHCP Option Formats . . . . . . . . . . . . . . . . . . . . . 6 2. DHCP Option Formats .............................................6
2.1 DHCPv6 GeoLoc Option . . . . . . . . . . . . . . . . . . 6 2.1. DHCPv6 GeoLoc Option .......................................6
2.2 DHCPv4 Options . . . . . . . . . . . . . . . . . . . . . 8 2.2. DHCPv4 Options .............................................8
2.3 Latitude and Longitude Fields . . . . . . . . . . . . . 11 2.3. Latitude and Longitude Fields .............................11
2.4 Altitude . . . . . . . . . . . . . . . . . . . . . . . . 14 2.4. Altitude ..................................................14
2.5 Datum . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.5. Datum .....................................................16
3. Security Considerations. . . . . . . . . . . . . . . . . . . . 17 3. Security Considerations ........................................17
4. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 17 4. IANA Considerations ............................................17
4.1 DHCP Options . . . . . . . . . . . . . . . . . . . . . . 17 4.1. DHCP Options ..............................................17
4.2 Altitude Type Registry . . . . . . . . . . . . . . . . . 18 4.2. Altitude Type Registry ....................................18
4.3 Datum Registry . . . . . . . . . . . . . . . . . . . . . 18 4.3. Datum Registry ............................................18
4.4 GeoLoc Option Version Registry . . . . . . . . . . . . . 19 4.4. GeoLoc Option Version Registry ............................19
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 5. Acknowledgments ................................................20
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 6. References .....................................................20
6.1. Normative References . . . . . . . . . . . . . . . . . . 20 6.1. Normative References ......................................20
6.2. Informational References . . . . . . . . . . . . . . . . 21 6.2. Informative References ....................................21
Appendix A. GML Mapping . . . . . . . . . . . . . . . . . . . . . 23 Appendix A. GML Mapping ...........................................23
A.1. GML Templates . . . . . . . . . . . . . . . . . . . . . 23 A.1. GML Templates ............................................23
Appendix B. Calculations of Resolution . . . . . . . . . . . . . . 26 Appendix B. Calculations of Resolution ............................27
B.1. LCI of "White House" (Example 1) . . . . . . . . . . . . 27 B.1. Location Configuration Information of "White House"
B.2. LCI of "Sears Tower" (Example 2) . . . . . . . . . . . . 29 (Example 1) ..............................................27
Appendix C. Calculations of Uncertainty . . . . . . . . . . . . . 30 B.2. Location Configuration Information of "Sears Tower"
C.1 LCI of "Sydney Opera House" (Example 3) . . . . . . . . 30 (Example 2) ..............................................29
Appendix D. Changes from RFC 3825 . . . . . . . . . . . . . . . . 34 Appendix C. Calculations of Uncertainty ...........................30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 35 C.1. Location Configuration Information of "Sydney Opera
House" (Example 3) .......................................30
Appendix D. Changes from RFC 3825 .................................34
1. Introduction 1. Introduction
The physical location of a network device has a range of The physical location of a network device has a range of
applications. In particular, emergency telephony applications rely applications. In particular, emergency telephony applications rely
on knowing the location of a caller in order to determine the correct on knowing the location of a caller in order to determine the correct
emergency center. emergency center.
The location of a device can be represented either in terms of The location of a device can be represented either in terms of
geospatial (or geodetic) coordinates, or as a civic address. geospatial (or geodetic) coordinates, or as a civic address.
skipping to change at page 4, line 30 skipping to change at page 4, line 17
based geographic location of the client, to be provided by the based geographic location of the client, to be provided by the
server. "Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) server. "Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6)
Option for Civic Addresses Configuration Information" [RFC4776] Option for Civic Addresses Configuration Information" [RFC4776]
specifies DHCP options for civic addresses. specifies DHCP options for civic addresses.
The geodetic coordinate options defined in this document and the The geodetic coordinate options defined in this document and the
civic address options defined in RFC 4776 [RFC4776] enable a DHCP civic address options defined in RFC 4776 [RFC4776] enable a DHCP
client to obtain its location. For example, a wired Ethernet host client to obtain its location. For example, a wired Ethernet host
might use these options for location determination. In this case, might use these options for location determination. In this case,
the location information could be derived from a wiremap by the DHCP the location information could be derived from a wiremap by the DHCP
server, using the Circuit-ID Relay Agent Information Option (RAIO) server, using the Circuit ID Relay Agent Information Option (RAIO)
defined (as Sub-Option 1) in RFC 3046 [RFC3046]. The DHCP server defined (as Sub-Option 1) in RFC 3046 [RFC3046]. The DHCP server
could correlate the Circuit-ID with the geographic location where the could correlate the Circuit ID with the geographic location where the
identified circuit terminates (such as the location of the wall identified circuit terminates (such as the location of the wall
jack). jack).
The mechanism defined here may also be utilized to provide location The mechanism defined here may also be utilized to provide location
to wireless hosts. DHCP relay agent sub-options (RAIO) [RFC3046] is to wireless hosts. DHCP relay agent sub-options (RAIO) [RFC3046]
one method a DHCP server might use to perform host location provide one method a DHCP server might use to perform host location
determination. Currently, the relay agent sub-options do not include determination. Currently, the relay agent sub-options do not include
data sets required for device level location determination of data sets required for device-level location determination of
wireless hosts. In cases where the DHC server uses RAIO for location wireless hosts. In cases where the DHCP server uses RAIO for
determination, a wireless host can use this mechanism to discover location determination, a wireless host can use this mechanism to
location of the radio access point, or the area of coverage for the discover the location of the radio access point, or the area of
radio access point. coverage for the radio access point.
An important feature of this specification is that after the relevant An important feature of this specification is that after the relevant
DHCP exchanges have taken place, the location information is stored DHCP exchanges have taken place, the location information is stored
on the end device rather than somewhere else, where retrieving it on the end device rather than somewhere else, where retrieving it
might be difficult in practice. might be difficult in practice.
1.1. Conventions used in this document 1.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
1.2. Resolution and Uncertainty 1.2. Resolution and Uncertainty
The DHCP options defined in this document include fields quantifying The DHCP options defined in this document include fields quantifying
the resolution or uncertainty associated with a target location. No the resolution or uncertainty associated with a target location. No
inferences relating to privacy policies can be drawn from either inferences relating to privacy policies can be drawn from either
uncertainty or resolution values. uncertainty or resolution values.
As utilized in this document, resolution refers to the accuracy of a As utilized in this document, resolution refers to the accuracy of a
reported location, as expressed by the number of valid bits in each reported location, as expressed by the number of valid bits in each
of the Latitude, Longitude and Altitude fields. of the Latitude, Longitude, and Altitude fields.
The Latitude (LaRes), Longitude (LoRes), and Altitude (AltRes)
Resolution fields are encoded as 6-bit, unsigned integer values. In
the DHCPv4 GeoConf Option 123, the LaRes, LoRes, and AltRes fields
are used to encode the number of bits of resolution. The resolution
sub-fields accommodate the desire to easily adjust the precision of a
reported location. Contents beyond the claimed resolution MAY be
randomized to obscure greater precision that might be available.
In the context of location technology, uncertainty is a In the context of location technology, uncertainty is a
quantification of errors. Any method for determining location is quantification of errors. Any method for determining location is
subject to some sources of error; uncertainty describes the amount of subject to some sources of error; uncertainty describes the amount of
error that is present. Uncertainty might be the coverage area of a error that is present. Uncertainty might be the coverage area of a
wireless transmitter, the extent of a building or a single room. wireless transmitter, the extent of a building, or a single room.
Uncertainty is usually represented as an area within which the target Uncertainty is usually represented as an area within which the target
is located. In this document, each of the three axes can be assigned is located. In this document, each of the three axes can be assigned
an uncertainty value. In effect, this describes a rectangular prism, an uncertainty value. In effect, this describes a rectangular prism,
which may be used as a coarse representation of a more complex shape which may be used as a coarse representation of a more complex shape
that fits within it. See Section 2.3.2 for more detail on the that fits within it. See Section 2.3.2 for more detail on the
correspondence between shapes and uncertainty. correspondence between shapes and uncertainty.
When representing locations from sources that can quantify When representing locations from sources that can quantify
uncertainty, the goal is to find the smallest possible rectangular uncertainty, the goal is to find the smallest possible rectangular
skipping to change at page 5, line 48 skipping to change at page 5, line 43
minimum and maximum values on each axis and ensuring that the final minimum and maximum values on each axis and ensuring that the final
encoding covers these points. This increases the region of encoding covers these points. This increases the region of
uncertainty, but ensures that the region that is described uncertainty, but ensures that the region that is described
encompasses the target location. encompasses the target location.
The DHCPv4 option formats defined in this document support resolution The DHCPv4 option formats defined in this document support resolution
and uncertainty parameters. The DHCPv4 GeoConf Option 123 includes a and uncertainty parameters. The DHCPv4 GeoConf Option 123 includes a
resolution parameter for each of the dimensions of location. Since resolution parameter for each of the dimensions of location. Since
this resolution parameter need not apply to all dimensions equally, a this resolution parameter need not apply to all dimensions equally, a
resolution value is included for each of the three location elements. resolution value is included for each of the three location elements.
The DHCPv4 GeoLoc Option TBD1 as well as the DHCPv6 GeoLoc Option The DHCPv4 GeoLoc Option 144 as well as the DHCPv6 GeoLoc Option 63
TBD2 format utilize an uncertainty parameter. format utilize an uncertainty parameter.
Appendix A describes the mapping of DHCP option values to the Appendix A describes the mapping of DHCP option values to the
Geography Markup Language (GML). Appendix B of this document Geography Markup Language (GML). Appendix B of this document
provides examples showing the calculation of resolution values. provides examples showing the calculation of resolution values.
Appendix C provides an example demonstrating calculation of Appendix C provides an example demonstrating calculation of
uncertainty values. uncertainty values.
Since the Presence Information Data Format Location Object (PIDF-LO) Since the Presence Information Data Format Location Object (PIDF-LO)
[RFC4119][RFC5491] is used to conveying location and the associated [RFC4119] [RFC5491] is used to convey location and the associated
uncertainty within an emergency call [Convey], a mechanism is needed uncertainty within an emergency call [Convey], a mechanism is needed
to convert the information contained within the DHCPv4 and DHCPv6 to convert the information contained within the DHCPv4 and DHCPv6
options to PIDF-LO. This document describes the following options to PIDF-LO. This document describes the following
conversions: conversions:
DHCPv4 GeoConf Option 123 to PIDF-LO o DHCPv4 GeoConf Option 123 to PIDF-LO
DHCPv4 GeoLoc Option TBD1 and DHCPv6 GeoLoc Option TBD2 to PIDF-LO
PIDF-LO to DHCP GeoLoc Option TBD1 and DHCPv6 GeoLoc Option TBD2 o DHCPv4 GeoLoc Option 144 and DHCPv6 GeoLoc Option 63 to PIDF-LO
o PIDF-LO to DHCP GeoLoc Option 144 and DHCPv6 GeoLoc Option 63
Conversion to PIDF-LO does not increase uncertainty; conversion from Conversion to PIDF-LO does not increase uncertainty; conversion from
PIDF-LO to the DHCPv4 GeoLoc Option TBD1 and the DHCPv6 GeoLoc Option PIDF-LO to the DHCPv4 GeoLoc Option 144 and the DHCPv6 GeoLoc Option
TBD2 increases uncertainty by less than a factor of 2 in each 63 increases uncertainty by less than a factor of 2 in each
dimension. Since it is not possible to translate an arbitrary PIDF- dimension. Since it is not possible to translate an arbitrary
LO to the DHCP GeoConf Option 123 with a bounded increase in PIDF-LO to the DHCP GeoConf Option 123 with a bounded increase in
uncertainty, the conversion is not specified. uncertainty, the conversion is not specified.
2. DHCP Option Formats 2. DHCP Option Formats
This section defines the format for the DHCPv4 and DHCPv6 options. This section defines the format for the DHCPv4 and DHCPv6 options.
These options utilize a similar format, differing primarily in the These options utilize a similar format, differing primarily in the
option code. option code.
2.1. DHCPv6 GeoLoc Option 2.1. DHCPv6 GeoLoc Option
The format of the DHCPv6 [RFC3315] GeoLoc Option is as follows: The format of the DHCPv6 [RFC3315] GeoLoc Option is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code (TBD2) | OptLen | | Option Code (63) | OptLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LatUnc | Latitude + | LatUnc | Latitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lat (cont'd) | LongUnc | Longitude + | Lat (cont'd) | LongUnc | Longitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Longitude (cont'd) | AType | AltUnc | Altitude + | Longitude (cont'd) | AType | AltUnc | Altitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Altitude (cont'd) |Ver| Res |Datum| | Altitude (cont'd) |Ver| Res |Datum|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code: DHCP Option Code TBD2 (16 bits). Code: 16 bits. The code for the DHCP Option Code (63).
OptLen: Option Length. For version 1, the option length is 16. OptLen: Option Length. For version 1, the option length is 16.
LatUnc: 6 bits. When the Ver field = 1, this field represents LatUnc: 6 bits. When the Ver field = 1, this field represents
latitude uncertainty. The contents of this field is latitude uncertainty. The contents of this field are
undefined for other values of the Ver field. undefined for other values of the Ver field.
Latitude: a 34 bit fixed point value consisting of 9 bits of Latitude: A 34-bit fixed-point value consisting of 9 bits of
integer and 25 bits of fraction, interpreted as integer and 25 bits of fraction, interpreted as described
described in Section 2.3. in Section 2.3.
LongUnc: 6 bits. When the Ver field = 1, this field represents LongUnc: 6 bits. When the Ver field = 1, this field represents
longitude uncertainty. The contents of this field is longitude uncertainty. The contents of this field are
undefined for other values of the Ver field. undefined for other values of the Ver field.
Longitude: a 34 bit fixed point value consisting of 9 bits of Longitude: A 34-bit fixed-point value consisting of 9 bits of
integer and 25 bits of fraction, interpreted as integer and 25 bits of fraction, interpreted as described
described in Section 2.3. in Section 2.3.
AType: Altitude Type (4 bits), defined in Section 2.4. AType: 4 bits. Altitude Type, defined in Section 2.4.
AltUnc: 6 bits. When the Ver field = 1, this field represents AltUnc: 6 bits. When the Ver field = 1, this field represents
altitude uncertainty. The contents of this field is altitude uncertainty. The contents of this field are
undefined for other values of the Ver field. undefined for other values of the Ver field.
Altitude: A 30 bit value defined by the AType field, described in Altitude: A 30-bit value defined by the AType field, described in
Section 2.4. Section 2.4.
Ver: The Ver field is two bits, providing for four potential Ver: The Ver field is 2 bits, providing for four potential
versions. This specification defines the behavior of versions. This specification defines the behavior of
version 1. The Ver field is always located at the same version 1. The Ver field is always located at the same
offset from the beginning of the option, regardless of offset from the beginning of the option, regardless of
the version in use. DHCPv6 clients implementing this the version in use. DHCPv6 clients implementing this
specification MUST support receiving version 1 specification MUST support receiving version 1 responses.
responses. DHCPv6 servers implementing this DHCPv6 servers implementing this specification MUST send
specification MUST send version 1 responses. version 1 responses.
Res: The Res field which is 3 bits, is reserved. These bits Res: 3 bits. The Res field is reserved. These bits have been
have been used by [IEEE-802.11y], but are not defined used by [IEEE-802.11y], but are not defined within this
within this specification. specification.
Datum: 3 bits. The Map Datum used for the coordinates given in Datum: 3 bits. The Map Datum used for the coordinates given in
this Option. this option.
2.2. DHCPv4 Options 2.2. DHCPv4 Options
2.2.1. DHCPv4 GeoConf Option 2.2.1. DHCPv4 GeoConf Option
The format of the DHCPv4 GeoConf Option is as follows: The format of the DHCPv4 GeoConf Option is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code 123 | Length | LaRes | Latitude + | Code 123 | Length | LaRes | Latitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latitude (cont'd) | LoRes | + | Latitude (cont'd) | LoRes | +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Longitude | | Longitude |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AType | AltRes | Altitude + | AType | AltRes | Altitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Alt.(cont'd) | Res |Datum| | Alt.(cont'd) | Res |Datum|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code: 8 bits. The code for the DHCPv4 GeoConf Option (123). Code: 8 bits. The code for the DHCPv4 GeoConf Option (123).
Length: 8 bits. The length of the option, in octets. Length: 8 bits. The length of the option, in octets.
The option length is 16. The option length is 16.
LaRes: 6 bits. This field represents latitude resolution. LaRes: 6 bits. This field represents latitude resolution.
Latitude: a 34 bit fixed point value consisting of 9 bits of Latitude: A 34-bit fixed-point value consisting of 9 bits of signed
signed integer and 25 bits of fraction, interpreted integer and 25 bits of fraction, interpreted as described
as described in Section 2.3. in Section 2.3.
LoRes: 6 bits. This field represents longitude resolution. LoRes: 6 bits. This field represents longitude resolution.
Longitude: a 34 bit fixed point value consisting of 9 bits of Longitude: A 34-bit fixed-point value consisting of 9 bits of signed
signed integer and 25 bits of fraction, interpreted integer and 25 bits of fraction, interpreted as described
as described in Section 2.3. in Section 2.3.
AType: Altitude Type (4 bits), defined in Section 2.4. AType: 4 bits. Altitude Type, defined in Section 2.4.
AltRes: 6 bits. This field represents altitude resolution. AltRes: 6 bits. This field represents altitude resolution.
Altitude: A 30 bit value defined by the AType field, described in Altitude: A 30-bit value defined by the AType field, described in
Section 2.4. Section 2.4.
Res: The Res field which is 5 bits, is reserved. These bits Res: 5 bits. The Res field is reserved. These bits have been
have been used by IEEE 802.11y [IEEE-802.11y], but are used by IEEE 802.11y [IEEE-802.11y], but are not defined
not defined within this specification. within this specification.
Datum: 3 bits. The Map Datum used for the coordinates given in Datum: 3 bits. The Map Datum used for the coordinates given in
this Option. this option.
2.2.2. DHCPv4 GeoLoc Option 2.2.2. DHCPv4 GeoLoc Option
The format of DHCPv4 GeoLoc Option is as follows: The format of the DHCPv4 GeoLoc Option is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code TBD1 | Length | LatUnc | Latitude + | Code 144 | Length | LatUnc | Latitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latitude (cont'd) | LongUnc | + | Latitude (cont'd) | LongUnc | +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Longitude | | Longitude |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AType | AltUnc | Altitude + | AType | AltUnc | Altitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Alt.(cont'd) |Ver| Res |Datum| | Alt.(cont'd) |Ver| Res |Datum|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code: 8 bits. The code for the DHCPv4 GeoLoc Option (TBD1). Code: 8 bits. The code for the DHCPv4 GeoLoc Option (144).
Length: 8 bits. The length of the option, in octets. Length: 8 bits. The length of the option, in octets.
For version 1, the option length is 16. For version 1, the option length is 16.
LatUnc: 6 bits. When the Ver field = 1, this field represents LatUnc: 6 bits. When the Ver field = 1, this field represents
latitude uncertainty. The contents of this field is latitude uncertainty. The contents of this field are
undefined for other values of the Ver field. undefined for other values of the Ver field.
Latitude: a 34 bit fixed point value consisting of 9 bits of Latitude: A 34-bit fixed-point value consisting of 9 bits of
integer and 25 bits of fraction, interpreted as integer and 25 bits of fraction, interpreted as described
described in Section 2.3. in Section 2.3.
LongUnc: 6 bits. When the Ver field = 1, this field represents LongUnc: 6 bits. When the Ver field = 1, this field represents
longitude uncertainty. The contents of this field is longitude uncertainty. The contents of this field are
undefined for other values of the Ver field. undefined for other values of the Ver field.
Longitude: a 34 bit fixed point value consisting of 9 bits of Longitude: A 34-bit fixed-point value consisting of 9 bits of
integer and 25 bits of fraction, interpreted as integer and 25 bits of fraction, interpreted as described
described in Section 2.3. in Section 2.3.
AType: Altitude Type (4 bits), defined in Section 2.4. AType: 4 bits. Altitude Type, defined in Section 2.4.
AltUnc: 6 bits. When the Ver field = 1, this field represents AltUnc: 6 bits. When the Ver field = 1, this field represents
altitude uncertainty. The contents of this field is altitude uncertainty. The contents of this field are
undefined for other values of the Ver field. undefined for other values of the Ver field.
Altitude: A 30 bit value defined by the AType field, described in Altitude: A 30-bit value defined by the AType field, described in
Section 2.4. Section 2.4.
Ver: The Ver field is two bits, providing for four potential Ver: The Ver field is 2 bits, providing for four potential
versions. This specification defines the behavior of versions. This specification defines the behavior of
version 1. The Ver field is always located at the same version 1. The Ver field is always located at the same
offset from the beginning of the option, regardless of offset from the beginning of the option, regardless of
the version in use. the version in use.
Res: The Res field which is 3 bits, is reserved. These bits Res: 3 bits. The Res field is reserved. These bits have been
have been used by [IEEE-802.11y], but are not defined used by [IEEE-802.11y], but are not defined within this
within this specification. specification.
Datum: 3 bits. The Map Datum used for the coordinates given in Datum: 3 bits. The Map Datum used for the coordinates given in
this Option. this option.
2.2.3. Option Support 2.2.3. Option Support
2.2.3.1. Client Support 2.2.3.1. Client Support
DHCPv4 clients implementing this specification MUST support receiving DHCPv4 clients implementing this specification MUST support receiving
the DHCPv4 GeoLoc Option TBD1 (version 1), and MAY support receiving the DHCPv4 GeoLoc Option 144 (version 1), and MAY support receiving
the DHCPv4 GeoConf Option 123 (originally defined in RFC 3825 the DHCPv4 GeoConf Option 123 (originally defined in RFC 3825
[RFC3825]). [RFC3825]).
DHCPv4 clients request the DHCPv4 server to send GeoConf Option 123, DHCPv4 clients request the DHCPv4 server to send GeoConf Option 123,
GeoLoc Option TBD1 or both via inclusion of the Parameter Request GeoLoc Option 144, or both via inclusion of the Parameter Request
List option. As noted in Section 9.8 of RFC 2132 [RFC2132]: List option. As noted in Section 9.8 of RFC 2132 [RFC2132]:
This option is used by a DHCP client to request values for This option is used by a DHCP client to request values for
specified configuration parameters. The list of requested specified configuration parameters. The list of requested
parameters is specified as n octets, where each octet is a valid parameters is specified as n octets, where each octet is a valid
DHCP option code as defined in this document. DHCP option code as defined in this document.
The client MAY list the options in order of preference. The DHCP The client MAY list the options in order of preference. The DHCP
server is not required to return the options in the requested server is not required to return the options in the requested
order, but MUST try to insert the requested options in the order order, but MUST try to insert the requested options in the order
requested by the client. requested by the client.
When DHCPv4 and DHCPv6 clients implementing this specification do not When DHCPv4 and DHCPv6 clients implementing this specification do not
understand a datum value, they MUST assume a World Geodesic System understand a datum value, they MUST assume a World Geodetic System
1984 (WGS84) [WGS84] datum (EPSG [EPSG] 4326 or 4979, depending on 1984 (WGS84) [WGS84] datum (European Petroleum Survey Group (EPSG)
whether there is an Altitude value present) and proceed accordingly. [EPSG] 4326 or 4979, depending on whether there is an altitude value
Assuming that a less accurate location value is better than none, present) and proceed accordingly. Assuming that a less accurate
this ensures that some (perhaps less accurate) location is available location value is better than none, this ensures that some (perhaps
to the client. less accurate) location is available to the client.
2.2.3.2. Server Option Selection 2.2.3.2. Server Option Selection
A DHCPv4 server implementing this specification MUST support sending A DHCPv4 server implementing this specification MUST support sending
GeoLoc Option TBD1 version 1 and SHOULD support sending GeoConf GeoLoc Option 144 version 1 and SHOULD support sending GeoConf Option
Option 123 in responses. 123 in responses.
A DHCPv4 server that provides location information SHOULD honor the A DHCPv4 server that provides location information SHOULD honor the
Parameter Request List included by the DHCPv4 client in order to Parameter Request List included by the DHCPv4 client in order to
decide whether to send GeoConf Option 123, GeoLoc Option TBD1 or both decide whether to send GeoConf Option 123, GeoLoc Option 144, or both
in the Response. in the Response.
2.3. Latitude and Longitude Fields 2.3. Latitude and Longitude Fields
The Latitude and Longitude values in this specification are encoded The latitude and longitude values in this specification are encoded
as 34 bit, twos complement, fixed point values with 9 integer bits as 34-bit, two's complement, fixed-point values with 9 integer bits
and 25 fractional bits. The exact meaning of these values is and 25 fractional bits. The exact meaning of these values is
determined by the datum; the description in this section applies to determined by the datum; the description in this section applies to
the datums defined in this document. This document uses the same the datums defined in this document. This document uses the same
definition for all datums it specifies. definition for all datums it specifies.
When encoding, Latitude and Longitude values are rounded to the When encoding, latitude and longitude values are rounded to the
nearest 34-bit binary representation. This imprecision is considered nearest 34-bit binary representation. This imprecision is considered
acceptable for the purposes to which this form is intended to be acceptable for the purposes to which this form is intended to be
applied and is ignored when decoding. applied and is ignored when decoding.
Positive latitudes are north of the equator and negative latitudes Positive latitudes are north of the equator, and negative latitudes
are south of the equator. Positive longitudes are east of the Prime are south of the equator. Positive longitudes are east of the Prime
Meridian (Greenwich) and negative (2s complement) longitudes are west Meridian, and negative (two's complement) longitudes are west of the
of the Prime Meridian. Prime Meridian.
Within the coordinate reference systems defined in this document Within the coordinate reference systems defined in this document
(Datum values 1-3), longitude values outside the range of -180 to 180 (Datum values 1-3), longitude values outside the range of -180 to 180
decimal degrees or latitude values outside the range of -90 to 90 decimal degrees or latitude values outside the range of -90 to 90
degrees MUST be considered invalid. Server implementations SHOULD degrees MUST be considered invalid. Server implementations SHOULD
prevent the entry of invalid values within the selected coordinate prevent the entry of invalid values within the selected coordinate
reference system. Location consumers MUST ignore invalid location reference system. Location consumers MUST ignore invalid location
coordinates and SHOULD log invalid location errors. coordinates and SHOULD log errors related to invalid location.
2.3.1. Latitude and Longitude Resolution 2.3.1. Latitude and Longitude Resolution
The Latitude (LaRes), Longitude (LoRes) and Altitude (AltRes)
Resolution fields are encoded as 6 bit, unsigned integer values. In
the DHCPv4 GeoConf Option 123, the LaRes, LoRes and AltRes fields are
used to encode the number of bits of resolution. The resolution sub-
fields accommodate the desire to easily adjust the precision of a
reported location. Contents beyond the claimed resolution MAY be
randomized to obscure greater precision that might be available.
In the DHCPv4 GeoConf Option 123, the LaRes value encodes the number In the DHCPv4 GeoConf Option 123, the LaRes value encodes the number
of high-order latitude bits that should be considered valid. Any of high-order latitude bits that MUST be considered valid. Any bits
bits entered to the right of this limit should not be considered entered to the right of this limit MUST NOT be considered valid and
valid and might be purposely false, or zeroed by the sender. The might be purposely false, or zeroed by the sender. The examples in
examples in Appendix B illustrate that a smaller value in the Appendix B illustrate that a smaller value in the resolution field
resolution field increases the area within which the device is increases the area within which the device is located. A value of 2
located. A value of 2 in the LaRes field indicates a precision of no in the LaRes field indicates a precision of no greater than 1/6th
greater than 1/6th that of the globe (see the first example of that of the globe (see the first example of Appendix B). A value of
Appendix B). A value of 34 in the LaRes field indicates a precision 34 in the LaRes field indicates a precision of about 3.11 mm in
of about 3.11 mm in latitude at the equator. latitude at the equator.
In the DHCPv4 GeoConf Option 123, the LoRes value encodes the number In the DHCPv4 GeoConf Option 123, the LoRes value encodes the number
of high-order longitude bits that should be considered valid. Any of high-order longitude bits that MUST be considered valid. Any bits
bits entered to the right of this limit should not be considered entered to the right of this limit MUST NOT be considered valid and
valid and might be purposely false, or zeroed by the sender. A value might be purposely false, or zeroed by the sender. A value of 2 in
of 2 in the LoRes field indicates precision of no greater than 1/6th the LoRes field indicates precision of no greater than 1/6th that of
that of the globe (see the first example of Appendix B). A value of the globe (see the first example of Appendix B). A value of 34 in
34 in the LoRes field indicates a precision of about 2.42 mm in the LoRes field indicates a precision of about 2.42 mm in longitude
Longitude (at the equator). Because lines of longitude converge at (at the equator). Because lines of longitude converge at the poles,
the poles, the distance is smaller (better precision) for locations the distance is smaller (better precision) for locations away from
away from the equator. the equator.
2.3.2. Latitude and Longitude Uncertainty 2.3.2. Latitude and Longitude Uncertainty
In the DHCPv6 GeoLoc Option TBD2 and the DHCPv4 GeoLoc Option TBD1, In the DHCPv6 GeoLoc Option 63 and the DHCPv4 GeoLoc Option 144, the
the Latitude and Longitude Uncertainty fields (LatUnc and LongUnc) Latitude and Longitude Uncertainty fields (LatUnc and LongUnc)
quantify the amount of uncertainty in each of the Latitude and quantify the amount of uncertainty in each of the latitude and
Longitude values respectively. A value of 0 is reserved to indicate longitude values, respectively. A value of 0 is reserved to indicate
that the uncertainty is unknown; values greater than 34 are reserved. that the uncertainty is unknown; values greater than 34 are reserved.
A point within the region of uncertainty is selected to be the A point within the region of uncertainty is selected to be the
encoded point; the centroid of the region is often an appropriate encoded point; the centroid of the region is often an appropriate
choice. The value for uncertainty is taken as the distance from the choice. The value for uncertainty is taken as the distance from the
selected point to the furthest extreme of the region of uncertainty selected point to the furthest extreme of the region of uncertainty
on that axis. This is demonstrated in the figure below, which shows on that axis. This is demonstrated in the figure below, which shows
a two-dimensional polygon that is projected on each axis. In the a two-dimensional polygon that is projected on each axis. In the
figure, "X" marks the point that is selected; the ranges marked with figure, "X" marks the point that is selected; the ranges marked with
"U" is the uncertainty. "U" indicate the uncertainty.
___ ___________ ___ ___________
^ | / | ^ | / |
| | / | | | / |
| | / | | | / |
U | / | U | / |
| | ( | | | ( |
V | | | V | | |
--X | X | --X | X |
| | `---------. | | `---------.
| | | | | |
| | | | | |
| | | | | |
- `-------------------------' - `-------------------------'
|---------X---------------| |---------X---------------|
|<------U------>| |<------U------>|
Key Key
--- ---
V, ^ = vertical arrows, delimiting the vertical uncertainty range. V, ^ = vertical arrows, delimiting the vertical uncertainty range.
<> = horizontal arrows, delimiting the horizontal uncertainty <> = horizontal arrows, delimiting the horizontal uncertainty
range. range.
Uncertainty applies to each axis independently. Uncertainty applies to each axis independently.
The amount of uncertainty can be determined from the encoding by The amount of uncertainty can be determined from the encoding by
taking 2 to the power of 8, less the encoded value. As is shown in taking 2 to the power of 8, less the encoded value, as is shown in
the following formula, where "x" is the encoded integer value: the following formula, where "x" is the encoded integer value:
uncertainty = 2 ^ ( 8 - x ) uncertainty = 2 ^ ( 8 - x )
The result of this formula is expressed in degrees of latitude or The result of this formula is expressed in degrees of latitude or
longitude. The uncertainty is added to the base latitude or longitude. The uncertainty is added to the base latitude or
longitude value to determine the maximum value in the uncertainty longitude value to determine the maximum value in the uncertainty
range; similarly, the uncertainty is subtracted from the base value range; similarly, the uncertainty is subtracted from the base value
to determine the minimum value. Note that because lines of longitude to determine the minimum value. Note that because lines of longitude
converge at the poles, the actual distance represented by this converge at the poles, the actual distance represented by this
uncertainty changes with the distance from the equator. uncertainty changes with the distance from the equator.
If the maximum or minimum latitude values derived from applying If the maximum or minimum latitude values derived from applying
uncertainty are outside the range of -90 to +90, these values are uncertainty are outside the range of -90 to +90, these values are
trimmed to within this range. If the maximum or minimum longitude trimmed to within this range. If the maximum or minimum longitude
values derived from applying uncertainty are outside the range of values derived from applying uncertainty are outside the range of
-180 to +180, then these values are normalized to this range by -180 to +180, then these values are normalized to this range by
adding or subtracting 360 as necessary. adding or subtracting 360 as necessary.
The encoded value is determined by subtracting the next highest whole The encoded value is determined by subtracting the next highest whole
integer value for the base 2 logarithm of uncertainty from 8. As is integer value for the base 2 logarithm of uncertainty from 8, as is
shown by the following formula, where uncertainty is the midpoint of shown by the following formula, where uncertainty is the midpoint of
the known range less the lower bound of that range: the known range less the lower bound of that range:
x = 8 - ceil( log2( uncertainty ) ) x = 8 - ceil( log2( uncertainty ) )
Note that the result of encoding this value increases the range of Note that the result of encoding this value increases the range of
uncertainty to the next available power of two; subsequent repeated uncertainty to the next available power of two; subsequent repeated
encodings and decodings do not change the value. Only increasing encodings and decodings do not change the value. Only increasing
uncertainty means that the associated confidence does not have to uncertainty means that the associated confidence does not have to
decrease. decrease.
2.4. Altitude 2.4. Altitude
How the Altitude value is interpreted depends on the Altitude Type How the altitude value is interpreted depends on the Altitude Type
(AType) value and the selected datum. Three Altitude Type values are (AType) value and the selected datum. Three Altitude Type values are
defined in this document: unknown (0), meters (1) and floors (2). defined in this document: unknown (0), meters (1), and floors (2).
2.4.1. No Known Altitude (AType = 0) 2.4.1. No Known Altitude (AType = 0)
In some cases, the altitude of the location might not be provided. In some cases, the altitude of the location might not be provided.
An Altitude Type value of zero indicates that the altitude is not An Altitude Type value of zero indicates that the altitude is not
given to the client. In this case, the Altitude and Altitude given to the client. In this case, the Altitude and Altitude
Uncertainty fields can contain any value and MUST be ignored. Uncertainty fields can contain any value and MUST be ignored.
2.4.2. Altitude in Meters (AType = 1) 2.4.2. Altitude in Meters (AType = 1)
If the Altitude Type has a value of one, Altitude is measured in If the Altitude Type has a value of one, altitude is measured in
meters, in relation to the zero set by the vertical datum. For AType meters, in relation to the zero set by the vertical datum. For AType
= 1, the Altitude value is expressed as a 30 bit, fixed point, twos = 1, the altitude value is expressed as a 30-bit, fixed-point, two's
complement integer with 22 integer bits and 8 fractional bits. complement integer with 22 integer bits and 8 fractional bits.
2.4.3. Altitude in Floors (AType = 2) 2.4.3. Altitude in Floors (AType = 2)
A value of two for Altitude Type indicates that the Altitude value is A value of two for Altitude Type indicates that the altitude value is
measured in floors. Since altitude in meters may not be known within measured in floors. Since altitude in meters may not be known within
a building, a floor indication may be more useful. For AType = 2, a building, a floor indication may be more useful. For AType = 2,
the Altitude value is expressed as a 30 bit, fixed point, twos the altitude value is expressed as a 30-bit, fixed-point, two's
complement integer with 22 integer bits and 8 fractional bits. complement integer with 22 integer bits and 8 fractional bits.
This value is relevant only in relation to a building; the value is This value is relevant only in relation to a building; the value is
relative to the ground level of the building. Floors located below relative to the ground level of the building. Floors located below
ground level are represented by negative values. In some buildings ground level are represented by negative values. In some buildings,
it might not be clear which floor is at ground level or an it might not be clear which floor is at ground level, or an
intermediate floor might be hard to identify as such. Determining intermediate floor might be hard to identify as such. Determining
what floor is at ground level and what constitutes a sub-floor as what floor is at ground level and what constitutes a sub-floor as
opposed to an naturally numbered floor is left to local opposed to a naturally numbered floor is left to local
interpretation. interpretation.
Larger values represent floors that are farther away from floor 0 Larger values represent floors that are farther away from floor 0
such that: such that:
- if positive, the floor value is farther above the ground floor. - if positive, the floor value is farther above the ground floor.
- if negative, the floor value is farther below the ground floor. - if negative, the floor value is farther below the ground floor.
Non-integer values can be used to represent intermediate or sub- Non-integer values can be used to represent intermediate or
floors, such as mezzanine levels. Example: a mezzanine between floor sub-floors, such as mezzanine levels. Example: a mezzanine between
1 and floor 2 could be represented as a value of 1.25. Example: floor 1 and floor 2 could be represented as a value of 1.25.
mezzanines between floor 4 and floor 5 could be represented as values Example: mezzanines between floor 4 and floor 5 could be represented
of 4.5 and 4.75. as values of 4.5 and 4.75.
2.4.4. Altitude Resolution 2.4.4. Altitude Resolution
In the DHCPv4 GeoConf Option 123, the Altitude Resolution (AltRes) In the DHCPv4 GeoConf Option 123, the altitude resolution (AltRes)
value encodes the number of high-order altitude bits that should be value encodes the number of high-order altitude bits that should be
considered valid. Values above 30 (decimal) are undefined and considered valid. Values above 30 (decimal) are undefined and
reserved. reserved.
If the Altitude Type value is one (AType = 1), an AltRes value 0.0 If the Altitude Type value is one (AType = 1), an AltRes value of 0.0
would indicate unknown Altitude. The most precise altitude would would indicate an unknown altitude. The most precise altitude would
have an AltRes value of 30. Many values of AltRes would obscure any have an AltRes value of 30. Many values of AltRes would obscure any
variation due to vertical datum differences. variation due to vertical datum differences.
The AltRes field SHOULD be set to maximum precision when AType = 2 The AltRes field SHOULD be set to maximum precision when AType = 2
(floors) when a floor value is included in the DHCP Reply, or when (floors) when a floor value is included in the DHCP Reply, or when
AType = 0, to denote that the floor isn't known. An altitude coded AType = 0, to denote that the floor isn't known. An altitude coded
as AType = 2, AltRes = 30, and Altitude = 0.0 is meaningful even as AType = 2, AltRes = 30, and Altitude = 0.0 is meaningful even
outside a building, and represents ground level at the given latitude outside a building, and represents ground level at the given latitude
and longitude. and longitude.
2.4.5. Altitude Uncertainty 2.4.5. Altitude Uncertainty
In the DHCPv6 GeoLoc Option TBD2 or the DHCPv4 GeoLoc Option TBD1, In the DHCPv6 GeoLoc Option 63 or the DHCPv4 GeoLoc Option 144, the
the AltUnc value quantifies the amount of uncertainty in the Altitude AltUnc value quantifies the amount of uncertainty in the altitude
value. As with LatUnc and LongUnc, a value of 0 for AltUnc is value. As with LatUnc and LongUnc, a value of 0 for AltUnc is
reserved to indicate that Altitude Uncertainty is not known; values reserved to indicate that altitude uncertainty is not known; values
above 30 are also reserved. Altitude Uncertainty only applies to above 30 are also reserved. Altitude uncertainty only applies to
Altitude Type 1. Altitude Type 1.
The amount of Altitude Uncertainty can be determined by the following The amount of altitude uncertainty can be determined by the following
formula, where x is the encoded integer value: formula, where x is the encoded integer value:
Uncertainty = 2 ^ ( 21 - x ) Uncertainty = 2 ^ ( 21 - x )
This value uses the same units as the associated altitude. This value uses the same units as the associated altitude.
Similarly, a value for the encoded integer value can be derived by Similarly, a value for the encoded integer value can be derived by
the following formula: the following formula:
x = 21 - ceil( log2( uncertainty ) ) x = 21 - ceil( log2( uncertainty ) )
2.5. Datum 2.5. Datum
The Datum field determines how coordinates are organized and related The Datum field determines how coordinates are organized and related
to the real world. Three datums are defined in this document, based to the real world. Three datums are defined in this document, based
on the definitions in [OGP.Geodesy]: on the definitions in [OGP.Geodesy]:
1: WGS84 (Latitude, Longitude, Altitude): 1: WGS84 (Latitude, Longitude, Altitude): The World Geodetic System
The World Geodesic System 1984 [WGS84] coordinate reference 1984 [WGS84] coordinate reference system.
system.
This datum is identified by the European Petroleum Survey Group This datum is identified by the European Petroleum Survey Group
(EPSG)/International Association of Oil & Gas Producers (OGP) with (EPSG)/International Association of Oil & Gas Producers (OGP) with
the code 4979, or by the URN "urn:ogc:def:crs:EPSG::4979". the code 4979, or by the URN "urn:ogc:def:crs:EPSG::4979".
Without Altitude, this datum is identified by the EPSG/OGP code Without altitude, this datum is identified by the EPSG/OGP code
4326 and the URN "urn:ogc:def:crs:EPSG::4326". 4326 and the URN "urn:ogc:def:crs:EPSG::4326".
2: NAD83 (Latitude, Longitude) + NAVD88: 2: NAD83 (Latitude, Longitude) + NAVD88: This datum uses a
This datum uses a combination of the North American Datum 1983 combination of the North American Datum 1983 (NAD83) for
(NAD83) for horizontal (Latitude and Longitude) values, plus the horizontal (Latitude and Longitude) values, plus the North
North American Vertical Datum of 1988 (NAVD88) vertical datum. American Vertical Datum of 1988 (NAVD88) vertical datum.
This datum is used for referencing location on land (not near This datum is used for referencing location on land (not near
tidal water) within North America. tidal water) within North America.
NAD83 is identified by the EPSG/OGP code of 4269, or the URN NAD83 is identified by the EPSG/OGP code of 4269, or the URN
"urn:ogc:def:crs:EPSG::4269". NAVD88 is identified by the EPSG/ "urn:ogc:def:crs:EPSG::4269". NAVD88 is identified by the EPSG/
OGP code of 5703, or the URN "urn:ogc:def:crs:EPSG::5703". OGP code of 5703, or the URN "urn:ogc:def:crs:EPSG::5703".
3: NAD83 (Latitude, Longitude) + MLLW: 3: NAD83 (Latitude, Longitude) + MLLW: This datum uses a combination
This datum uses a combination of the North American Datum 1983 of the North American Datum 1983 (NAD83) for horizontal (Latitude
(NAD83) for horizontal (Latitude and Longitude) values, plus the and Longitude) values, plus the Mean Lower Low Water (MLLW)
Mean Lower Low Water (MLLW) vertical datum. vertical datum.
This datum is used for referencing location on or near tidal water This datum is used for referencing location on or near tidal water
within North America. within North America.
NAD83 is identified by the EPSG/OGP code of 4269, or the URN NAD83 is identified by the EPSG/OGP code of 4269, or the URN
"urn:ogc:def:crs:EPSG::4269". MLLW does not have a specific code "urn:ogc:def:crs:EPSG::4269". MLLW does not have a specific code
or URN. or URN.
All hosts MUST support the WGS84 datum (Datum 1). All hosts MUST support the WGS84 datum (Datum 1).
skipping to change at page 17, line 18 skipping to change at page 17, line 24
in "Geopriv Requirements" [RFC3693]. A threat analysis is provided in "Geopriv Requirements" [RFC3693]. A threat analysis is provided
in "Threat Analysis of the Geopriv Protocol" [RFC3694]. in "Threat Analysis of the Geopriv Protocol" [RFC3694].
Since there is no privacy protection for DHCP messages, an Since there is no privacy protection for DHCP messages, an
eavesdropper who can monitor the link between the DHCP server and eavesdropper who can monitor the link between the DHCP server and
requesting client can discover this LCI. requesting client can discover this LCI.
To minimize the unintended exposure of location information, the LCI To minimize the unintended exposure of location information, the LCI
option SHOULD be returned by DHCP servers only when the DHCP client option SHOULD be returned by DHCP servers only when the DHCP client
has included this option in its 'parameter request list' (Section 3.5 has included this option in its 'parameter request list' (Section 3.5
[RFC2131], Section 9.8 [RFC2132]). of [RFC2131], Section 9.8 of [RFC2132]).
Where critical decisions might be based on the value of this option, Where critical decisions might be based on the value of this option,
DHCP authentication as defined in "Authentication for DHCP Messages" DHCP authentication as defined in "Authentication for DHCP Messages"
[RFC3118] and "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)" [RFC3118] and "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)"
[RFC3315] SHOULD be used to protect the integrity of the DHCP [RFC3315] SHOULD be used to protect the integrity of the DHCP
options. options.
Link layer confidentiality and integrity protection may also be Link-layer confidentiality and integrity protection may also be
employed to reduce the risk of location disclosure and tampering. employed to reduce the risk of location disclosure and tampering.
4. IANA Considerations 4. IANA Considerations
4.1. DHCP Options 4.1. DHCP Options
This document defines the DHCPv6 GeoLoc option (see Section 2.1) This document defines the DHCPv6 GeoLoc Option (see Section 2.1),
which requires assignment of DHCPv6 option code TBD2 [RFC3315]: which has been assigned a DHCPv6 option code of 63 per [RFC3315]:
Value Description Reference Value Description Reference
---- ------------------ ---------- ---- ------------------ ----------
TBD2 OPTION_GEOLOCATION RFC xxxx 63 OPTION_GEOLOCATION RFC 6225
[RFC Editor: Please replace xxxx with the RFC number
assigned to this document.]
This document defines the DHCPv4 GeoConf option (see Section 2.2.1) This document defines the DHCPv4 GeoConf Option (see Section 2.2.1),
which has been assigned a DHCPv4 option code of 123 from the DHCP which has been assigned a DHCPv4 option code of 123 from the DHCP
Option space. Option space.
This document also defines the DHCPv4 GeoLoc option (see Section This document also defines the DHCPv4 GeoLoc Option (see
2.2.2) which requires assignment of DHCPv4 option code TBD1 Section 2.2.2), which has been assigned a DHCPv4 option code of 144
[RFC2132][RFC2939]: per [RFC2132] [RFC2939]:
Data Data
Tag Name Length Meaning Reference Tag Name Length Meaning Reference
---- ---- ------ ------- --------- ---- ---- ------ ------- ---------
TBD1 GeoLoc 16 Geospatial Location RFC xxxx 144 GeoLoc 16 Geospatial Location RFC 6225
with Uncertainty with Uncertainty
[RFC Editor: Please replace xxxx with the RFC number
assigned to this document.]
4.2. Altitude Type Registry 4.2. Altitude Type Registry
IANA is asked to create and maintain the Altitude Type registry IANA has created and now maintains the Altitude Type registry
following the guidelines below. following the guidelines below.
The registry consists of three values: Altitude Type, Description The registry consists of three values: Altitude Type, Description,
and Reference. These are described below. and Reference. These are described below.
Altitude Type: an integer, refers to the value used in the DHCPv4 Altitude Type: An integer, refers to the value used in the DHCPv4
GeoConf and the DHCPv4 and DHCPv6 GeoLoc Options described in this GeoConf and the DHCPv4 and DHCPv6 GeoLoc options described in this
document. Values from 0 to 15 are assigned. document. Values 0 - 2 are assigned. Values 3 - 15 are
Unassigned [RFC5226].
Description: the description of the altitude described by this code. Description: The description of the altitude described by this code.
Reference: the reference to the document that describes the altitude Reference: The reference to the document that describes the altitude
code. This reference MUST define the way that the 30 bit altitude code. This reference MUST define the way that the 30-bit altitude
values and the associated 6 bit uncertainty are interpreted. values and the associated 6-bit uncertainty are interpreted.
Initial values are given below; new assignments are to be made Initial values are given below; new assignments are to be made
following the "Standards Action" policies [RFC5226]. following the "Standards Action" policies [RFC5226].
+------+---------------------+--------------+ +------+---------------------+--------------+
| # | Description | Reference | | # | Description | Reference |
+------+---------------------+--------------+ +------+---------------------+--------------+
| 0 | No known altitude | RFC xxxx | | 0 | No known altitude | RFC 6225 |
| 1 | Altitude in meters | RFC xxxx | | 1 | Altitude in meters | RFC 6225 |
| 2 | Altitude in floors | RFC xxxx | | 2 | Altitude in floors | RFC 6225 |
| 3-15 | Unassigned | RFC xxxx | | 3-15 | Unassigned | |
+------+---------------------+--------------+ +------+---------------------+--------------+
[RFC Editor: Please replace xxxx with the RFC number
assigned to this document.]
4.3. Datum Registry 4.3. Datum Registry
IANA is asked to create and maintain the Datum registry following the IANA has created and now maintains the Datum registry following the
guidelines below. guidelines below.
The registry consists of three values: Datum, Description and The registry consists of three values: Datum, Description, and
Reference. These are described below. Reference. These are described below.
Datum: an integer, refers to the value used in the DHCPv4 GeoConf and Datum: An integer, refers to the value used in the DHCPv4 GeoConf and
the DHCPv4 and DHCPv6 GeoLoc Options described in this document. the DHCPv4 and DHCPv6 GeoLoc options described in this document.
Values from 1 to 7 are assigned. Value 0 is Reserved. Values 1 - 3 are assigned. Values 4 - 7 are
Unassigned [RFC5226].
Description: the description of the altitude described by this code. Description: The description of the altitude described by this code.
Reference: the reference to the document that describes the Datum Reference: The reference to the document that describes the Datum
code. This reference MUST include specification of both the code. This reference MUST include specification of both the
horizontal and vertical datum, and MUST define the way that the 34 horizontal and vertical datum, and MUST define the way that the
bit values and the respective 6 bit uncertainties are interpreted. 34-bit values and the respective 6-bit uncertainties are
interpreted.
Initial values are given below; new assignments are to be made Initial values are given below; new assignments are to be made
following the "Standards Action" policies [RFC5226]. following the "Standards Action" policies [RFC5226].
+------+----------------------------------------+--------------+ +------+----------------------------------------+--------------+
| # | Description | Reference | | # | Description | Reference |
+------+----------------------------------------+--------------+ +------+----------------------------------------+--------------+
| 0 | Reserved | RFC xxxx | | 0 | Reserved | RFC 6225 |
+------+----------------------------------------+--------------+ +------+----------------------------------------+--------------+
| 1 | Vertical datum WGS 84 defined by EPSG | RFC xxxx | | 1 | Vertical datum WGS 84 defined by EPSG | RFC 6225 |
| | CRS Code 4327 | | | | CRS Code 4327 | |
+------+----------------------------------------+--------------+ +------+----------------------------------------+--------------+
| 2 | Vertical datum NAD83 defined by EPSG | RFC xxxx | | 2 | Vertical datum NAD83 defined by EPSG | RFC 6225 |
| | CRS Code 4269 with North American | | | | CRS Code 4269 with North American | |
| | Vertical Datum of 1988 (NAVD88) | | | | Vertical Datum of 1988 (NAVD88) | |
+------+----------------------------------------+--------------+ +------+----------------------------------------+--------------+
| 3 | Vertical datum NAD83, defined by EPSG | RFC xxxx | | 3 | Vertical datum NAD83 defined by EPSG | RFC 6225 |
| | CRS Code 4269 with Mean Lower Low Water| | | | CRS Code 4269 with Mean Lower Low Water| |
| | (MLLW) as associated vertical datum | | | | (MLLW) as associated vertical datum | |
+------+----------------------------------------+--------------+ +------+----------------------------------------+--------------+
| 4-7 | Unassigned | RFC xxxx | | 4-7 | Unassigned | |
+------+----------------------------------------+--------------+ +------+----------------------------------------+--------------+
[RFC Editor: Please replace xxxx with the RFC number
assigned to this document.]
4.4. GeoLoc Option Version Registry 4.4. GeoLoc Option Version Registry
IANA is asked to create and maintain the GeoLoc Option Version IANA has created and now maintains the GeoLoc Option Version registry
registry following the guidelines below. following the guidelines below.
The registry consists of three values: GeoLoc Option Version, The registry consists of three values: GeoLoc Option Version,
Description and Reference. These are described below. Description, and Reference. These are described below.
GeoLoc Option Version: an integer, refers to the version used in the GeoLoc Option Version: An integer; refers to the version used in the
DHCPv4 and DHCPv6 GeoLoc Options described in this document. Values DHCPv4 and DHCPv6 GeoLoc options described in this document.
from 1 to 3 are assigned. Value 0 is Reserved. Value 1 has been assigned. Values 2 - 3 are
Unassigned [RFC5226].
Description: the description of the version described by this code. Description: The description of the version described by this code.
Reference: the reference to the document that describes the Version Reference: The reference to the document that describes the Version
code. code.
Initial values are given below; new assignments are to be made Initial values are given below; new assignments are to be made
following the "Standards Action" policies [RFC5226]. following the "Standards Action" policies [RFC5226].
+------+---------------------------------------+--------------+ +------+---------------------------------------+--------------+
| # | Description | Reference | | # | Description | Reference |
+------+---------------------------------------+--------------+ +------+---------------------------------------+--------------+
| 0 | Reserved | RFC xxxx | | 0 | Reserved | RFC 6225 |
+------+---------------------------------------+--------------+ +------+---------------------------------------+--------------+
| 1 | Implementations utilizing uncertainty | RFC xxxx | | 1 | Implementations utilizing uncertainty | RFC 6225 |
| | parameters for both DHCPv4 and DHCPv6 | | | | parameters for both DHCPv4 and DHCPv6 | |
| | GeoLoc options | | | | GeoLoc options | |
+------+---------------------------------------+--------------+ +------+---------------------------------------+--------------+
| 2-3 | Unassigned | RFC xxxx | | 2-3 | Unassigned | |
+------+---------------------------------------+--------------+ +------+---------------------------------------+--------------+
[RFC Editor: Please replace xxxx with the RFC number
assigned to this document.]
5. Acknowledgments 5. Acknowledgments
The authors would like to thank Randall Gellens, Patrik Falstrom, The authors would like to thank Randall Gellens, Patrik Falstrom,
Ralph Droms, Ted Hardie, Jon Peterson, Robert Sparks, Ralph Droms, Ralph Droms, Ted Hardie, Jon Peterson, Robert Sparks, Nadine Abbott,
Nadine Abbott and Mykyta Yevstifeyev for their inputs and and Mykyta Yevstifeyev for their inputs and constructive comments
constructive comments regarding this document. Additionally, the regarding this document. Additionally, the authors would like to
authors would like to thank Greg Troxel for the education on vertical thank Greg Troxel for the education on vertical datums, as well as
datums, as well as Carl Reed. Thanks to Richard Barnes for his Carl Reed. Thanks to Richard Barnes for his contribution on GML
contribution on GML mapping for resolution. mapping for resolution.
6. References 6. References
6.1. Normative References 6.1. Normative References
[EPSG] European Petroleum Survey Group, http://www.epsg.org/ and [EPSG] European Petroleum Survey Group,
http://www.epsg-registry.org/ <http://www.epsg.org/> and
<http://www.epsg-registry.org/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, [RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
March 1997. RFC 2131, March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP
Extensions", RFC2132, March 1997. Vendor Extensions", RFC 2132, March 1997.
[RFC2939] Droms, R., "Procedures and IANA Guidelines for Definition [RFC2939] Droms, R., "Procedures and IANA Guidelines for
of New DHCP Options and Message types", BCP 43, RFC 2939, Definition of New DHCP Options and Message Types",
September 2000. BCP 43, RFC 2939, September 2000.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC [RFC3118] Droms, R., Ed., and W. Arbaugh, Ed., "Authentication
3046, January 2001. for DHCP Messages", RFC 3118, June 2001.
[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T.,
Messages", RFC 3118, June 2001. Perkins, C., and M. Carney, "Dynamic Host
Configuration Protocol for IPv6 (DHCPv6)", RFC 3315,
July 2003.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing
M. Carney, "Dynamic Host Configuration Protocol for IPv6 an IANA Considerations Section in RFCs", BCP 26, RFC
(DHCPv6)", RFC 3315, July 2003. 5226, May 2008.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [WGS84] US National Imagery and Mapping Agency, "Department of
IANA Considerations Section in RFCs", RFC 5226, May 2008. Defense (DoD) World Geodetic System 1984 (WGS 84),
Third Edition", NIMA TR8350.2, January 2000,
<https://www1.nga.mil/PRODUCTSSERVICES/
GEODESYGEOPHYSICS/WORLDGEODETICSYSTEM/
Pages/default.aspx> and
<http://www.ngs.noaa.gov/faq.shtml#WGS84>.
[WGS84] US National Imagery and Mapping Agency, "Department of 6.2. Informative References
Defense (DoD) World Geodetic System 1984 (WGS 84), Third
Edition", NIMA TR8350.2, January 2000,
https://www1.nga.mil/PRODUCTSSERVICES/GEODESYGEOPHYSICS/
WORLDGEODETICSYSTEM/Pages/default.aspx and
http://www.ngs.noaa.gov/faq.shtml#WGS84
6.2. Informational References [Convey] Polk, J., Rosen, B., and J. Peterson, "Location
Conveyance for the Session Initiation Protocol", Work
in Progress, May 2011.
[Convey] Polk, J., Rosen, B. and J. Peterson, "Location Conveyance [GeoShape] Thomson, M. and C. Reed, "GML 3.1.1 PIDF-LO Shape
for the Session Initiation Protocol", Internet draft (work Application Schema for use by the Internet Engineering
in progress), draft-ietf-sipcore-location- Task Force (IETF)", Candidate OpenGIS Implementation
conveyance-06.txt, February 23, 2011. Specification 06-142, Version: 0.0.9, December 2006.
[GeoShape] Thomson, M. and C. Reed, "GML 3.1.1 PIDF-LO Shape [IEEE-802.11y] IEEE Standard for Information technology -
Application Schema for use by the Internet Engineering Task Telecommunications and information exchange between
Force (IETF)", Candidate OpenGIS Implementation systems - Local and metropolitan area networks -
Specification 06-142, Version: 0.0.9, December 2006. Specific requirements - Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY)
specifications Amendment 3: 3650-3700 MHz Operation in
USA, November 2008.
[IEEE-802.11y] [NENA] National Emergency Number Association (NENA), NENA
Information technology - Telecommunications and information Technical Information Document on Model Legislation
exchange between systems - Local and metropolitan area Enhanced 911 for Multi-Line Telephone Systems,
networks - Specific requirements - Part 11: Wireless LAN <www.nena.org>.
Medium Access Control (MAC) and Physical Layer (PHY)
specifications Amendment 3: 3650-3700 MHz Operation in USA,
November 2008.
[NENA] National Emergency Number Association (NENA) www.nena.org [OGC-GML3.1.1] Portele, C., Cox, S., Daisy, P., Lake, R., and A.
NENA Technical Information Document on Model Legislation Whiteside, "Geography Markup Language (GML) 3.1.1",
Enhanced 911 for Multi-Line Telephone Systems. OGC 03-105r1, July 2003.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC [OGP.Geodesy] International Association of Oil & Gas Producers (OGP)
3046, January 2001. Geodesy Resources, Geomatics Committee,
<http://info.ogp.org.uk/geodesy/>.
[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J. and J. [RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
Polk, "Geopriv Requirements", RFC 3693, February 2004. RFC 3046, January 2001.
[RFC3694] Danley, M., Mulligan, D., Morris, J. and J. Peterson, [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J.,
"Threat Analysis of the Geopriv Protocol", RFC 3694, and J. Polk, "Geopriv Requirements", RFC 3693,
February 2004. February 2004.
[RFC3825] Polk, J., Schnizlein, J. and M. Linsner, "Dynamic Host [RFC3694] Danley, M., Mulligan, D., Morris, J., and J. Peterson,
Configuration Protocol Option for Coordinate-based Location "Threat Analysis of the Geopriv Protocol", RFC 3694,
Configuration Information", RFC 3825, July 2004. February 2004.
[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object [RFC3825] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic
Format", RFC 4119, December 2005. Host Configuration Protocol Option for Coordinate-
based Location Configuration Information", RFC 3825,
July 2004.
[RFC4776] Schulzrinne, H., "Dynamic Host Configuration Protocol [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location
(DHCPv4 and DHCPv6) Option for Civic Addresses Object Format", RFC 4119, December 2005.
Configuration Information", RFC 4776, November 2006.
[RFC5139] Thomson, M. and J. Winterbottom, "Revised Civic Location [RFC4776] Schulzrinne, H., "Dynamic Host Configuration Protocol
Format for Presence Information Data Format Location Object (DHCPv4 and DHCPv6) Option for Civic Addresses
(PIDF-LO)", RFC 5139, February 2008. Configuration Information", RFC 4776, November 2006.
[RFC5491] Winterbottom, J., Thomson, M. and H. Tschofenig, "GEOPRIV [RFC5139] Thomson, M. and J. Winterbottom, "Revised Civic
PIDF-LO Usage Clarification, Considerations, and Location Format for Presence Information Data Format
Recommendations ", RFC 5491, March 2009 Location Object (PIDF-LO)", RFC 5139, February 2008.
Appendix A. GML Mapping [RFC5491] Winterbottom, J., Thomson, M., and H. Tschofenig,
"GEOPRIV Presence Information Data Format Location
Object (PIDF-LO) Usage Clarification, Considerations,
and Recommendations", RFC 5491, March 2009.
Appendix A. GML Mapping
The GML representation of a decoded DHCP option depends on what The GML representation of a decoded DHCP option depends on what
fields are specified. The DHCP format for location logically fields are specified. The DHCP format for location logically
describes a geodetic prism, rectangle, or point, depending on whether describes a geodetic prism, rectangle, or point, depending on whether
Altitude and uncertainty values are provided. In the absence of altitude and uncertainty values are provided. In the absence of
uncertainty information, the value decoded from the DHCP form can be uncertainty information, the value decoded from the DHCP form can be
expressed as a single point; this is true regardless of whether the expressed as a single point; this is true regardless of whether the
version 0 or version 1 interpretations of the uncertainty fields are version 0 or version 1 interpretations of the uncertainty fields are
used. If the point includes Altitude, it uses a three dimensional used. If the point includes altitude, it uses a three-dimensional
CRS, otherwise it uses a two dimensional CRS. If all fields are Coordinate Reference System (CRS); otherwise, it uses a two-
included along with uncertainty, the shape described is a rectangular dimensional CRS. If all fields are included along with uncertainty,
prism. Note that this is necessary given that uncertainty for each the shape described is a rectangular prism. Note that this is
axis is provided independently. necessary given that uncertainty for each axis is provided
independently.
If Altitude or Altitude Uncertainty (AltUnc) is not specified, the If altitude or altitude uncertainty (AltUnc) is not specified, the
shape is described as a rectangle using the "gml:Polygon" shape. If shape is described as a rectangle using the "gml:Polygon" shape. If
Altitude is available, a three dimensional CRS is used, otherwise a altitude is available, a three-dimensional CRS is used; otherwise, a
two dimensional CRS is used. two-dimensional CRS is used.
For Datum values of 2 or 3 (NAD83), there is no available CRS URN For Datum values of 2 or 3 (NAD83), there is no available CRS URN
that covers three dimensional coordinates. By necessity, locations that covers three-dimensional coordinates. By necessity, locations
described in these datums can be represented by two dimensional described in these datums can be represented by two-dimensional
shapes only; that is, either a two dimensional point or a polygon. shapes only; that is, either a two-dimensional point or a polygon.
If the Altitude Type is 2 (floors), then this value can be If the Altitude Type is 2 (floors), then this value can be
represented using a civic address object [RFC5139] that is presented represented using a civic address object [RFC5139] that is presented
alongside the geodetic object. alongside the geodetic object.
This Appendix describes how the location value encoded in DHCP format This Appendix describes how the location value encoded in DHCP format
for geodetic location can be expressed in GML. The mapping is valid for geodetic location can be expressed in GML. The mapping is valid
for the DHCPv6 GeoLoc Option as well as both of the DHCPv4 GeoConf for the DHCPv6 GeoLoc Option as well as both of the DHCPv4 GeoConf
and GeoLoc options, and for the currently-defined datum values (1, 2, and GeoLoc options, and for the currently defined datum values (1, 2,
and 3). Further version or datum definitions should provide similar and 3). Further version or datum definitions should provide similar
mappings. mappings.
These shapes can be mapped to GML by first computing the bounds that These shapes can be mapped to GML by first computing the bounds that
are described using the coordinate and uncertainty fields, then are described using the coordinate and uncertainty fields, then
encoding the result in a GML Polygon or Prism shape. encoding the result in a GML Polygon or Prism shape.
A.1. GML Templates A.1. GML Templates
If Altitude is provided in meters (AType 1) and the datum value is If altitude is provided in meters (AType 1) and the datum value is
WGS84 (value 1), then the proper GML shape is a Prism, with the WGS84 (value 1), then the proper GML shape is a Prism, with the
following form (where $value$ indicates a value computed from the following form (where $value$ indicates a value computed from the
DHCP option as described below): DHCP option as described below):
<gs:Prism srsName="urn:ogc:def:crs:EPSG::4979" <gs:Prism srsName="urn:ogc:def:crs:EPSG::4979"
xmlns:gs="http://www.opengis.net/pidflo/1.0" xmlns:gs="http://www.opengis.net/pidflo/1.0"
xmlns:gml="http://www.opengis.net/gml"> xmlns:gml="http://www.opengis.net/gml">
<gs:base> <gs:base>
<gml:Polygon> <gml:Polygon>
<gml:exterior> <gml:exterior>
<gml:LinearRing> <gml:LinearRing>
<gml:posList> <gml:posList>
$lowLatitude$ $lowLongitude$ $lowAltitude$ $lowLatitude$ $lowLongitude$ $lowAltitude$
$lowLatitude$ $highLongitude$ $lowAltitude$ $lowLatitude$ $highLongitude$ $lowAltitude$
$highLatitude$ $highLongitude$ $lowAltitude$ $highLatitude$ $highLongitude$ $lowAltitude$
$highLatitude$ $lowLongitude$ $lowAltitude$ $highLatitude$ $lowLongitude$ $lowAltitude$
$lowLatitude$ $lowLongitude$ $lowAltitude$ $lowLatitude$ $lowLongitude$ $lowAltitude$
</gml:posList> </gml:posList>
</gml:LinearRing> </gml:LinearRing>
</gml:exterior> </gml:exterior>
</gml:Polygon> </gml:Polygon>
</gs:base> </gs:base>
<gs:height uom="urn:ogc:def:uom:EPSG::9001"> <gs:height uom="urn:ogc:def:uom:EPSG::9001">
$highAltitude - lowAltitude$ $highAltitude - lowAltitude$
</gs:height> </gs:height>
</gs:Prism> </gs:Prism>
The Polygon shape is used if Altitude is omitted or specified in The Polygon shape is used if altitude is omitted or specified in
floors, or if either NAD83 datum is used (value 2 or 3). The floors, or if either NAD83 datum is used (value 2 or 3). The
corresponding GML Polygon has the following form: corresponding GML Polygon has the following form:
<gml:Polygon srsName="$2D-CRS-URN$" <gml:Polygon srsName="$2D-CRS-URN$"
xmlns:gml="http://www.opengis.net/gml">> xmlns:gml="http://www.opengis.net/gml">>
<gml:exterior> <gml:exterior>
<gml:LinearRing> <gml:LinearRing>
<gml:posList> <gml:posList>
$lowLatitude$ $lowLongitude$ $lowLatitude$ $lowLongitude$
$lowLatitude$ $highLongitude$ $lowLatitude$ $highLongitude$
$highLatitude$ $highLongitude$ $highLatitude$ $highLongitude$
$highLatitude$ $lowLongitude$ $highLatitude$ $lowLongitude$
$lowLatitude$ $lowLongitude$ $lowLatitude$ $lowLongitude$
</gml:posList> </gml:posList>
</gml:LinearRing> </gml:LinearRing>
</gml:exterior> </gml:exterior>
</gml:Polygon> </gml:Polygon>
The value "2D-CRS-URN" is defined by the datum value: If the datum is The value "2D-CRS-URN" is defined by the datum value: If the datum is
WGS84 (value 1), then the 2D-CRS-URN is "urn:ogc:def:crs:EPSG::4326". WGS84 (value 1), then the 2D-CRS-URN is "urn:ogc:def:crs:EPSG::4326".
If the datum is NAD83 (value 2 or 3), then the 2D-CRS-URN is If the datum is NAD83 (value 2 or 3), then the 2D-CRS-URN is
"urn:ogc:def:crs:EPSG::4269". "urn:ogc:def:crs:EPSG::4269".
A Polygon shape with the WGS84 three-dimensional CRS is used if the A Polygon shape with the WGS84 three-dimensional CRS is used if the
datum is WGS84 (value 1) and the Altitude is specified in meters datum is WGS84 (value 1) and the altitude is specified in meters
(Altitude type 1), but no Altitude uncertainty is specified (that is, (Altitude Type 1), but no altitude uncertainty is specified (that is,
AltUnc is 0). In this case, the value of the Altitude field is added AltUnc is 0). In this case, the value of the Altitude field is added
after each of the points above, and the srsName attribute is set to after each of the points above, and the srsName attribute is set to
the three-dimensional WGS84 CRS, namely "urn:ogc:def:crs:EPSG::4979". the three-dimensional WGS84 CRS, namely "urn:ogc:def:crs:EPSG::4979".
A simple point shape is used if either Latitude uncertainty (LatUnc) A simple point shape is used if either latitude uncertainty (LatUnc)
or Longitude uncertainty (LongUnc) is not specified. With Altitude, or longitude uncertainty (LongUnc) is not specified. With altitude,
this uses a three-dimensional CRS; otherwise, it uses a two- this uses a three-dimensional CRS; otherwise, it uses a two-
dimensional CRS. dimensional CRS.
<gml:Point srsName="$CRS-URN$" <gml:Point srsName="$CRS-URN$"
xmlns:gml="http://www.opengis.net/gml"> xmlns:gml="http://www.opengis.net/gml">
<gml:pos>$Latitude$ $Longitude$ $[Altitude]$</gml:pos> <gml:pos>$Latitude$ $Longitude$ $[Altitude]$</gml:pos>
</gml:Point> </gml:Point>
A.1.1. Finding Low and High Values using Uncertainty Fields A.1.1. Finding Low and High Values Using Uncertainty Fields
For the DHCPv4 GeoConf Option 123, resolution fields are used (LaRes, For the DHCPv4 GeoConf Option 123, resolution fields are used (LaRes,
LoRes, AltRes), indicating how many bits of a value contain LoRes, AltRes), indicating how many bits of a value contain
information. Any bits beyond those indicated can be either zero or information. Any bits beyond those indicated can be either zero or
one. one.
For the DHCPv6 GeoLoc Option TBD2 and DHCPv4 GeoLoc Option TBD1, the For the DHCPv6 GeoLoc Option 63 and DHCPv4 GeoLoc Option 144, the
LatUnc, LongUnc and AltUnc fields indicate uncertainty distances, LatUnc, LongUnc, and AltUnc fields indicate uncertainty distances,
denoting the bounds of the location region described by the DHCP denoting the bounds of the location region described by the DHCP
location object. location object.
The two sections below describe how to compute the Latitude, The two sections below describe how to compute the latitude,
Longitude, and Altitude bounds (e.g., $lowLatitude$, $highAltitude$) longitude, and altitude bounds (e.g., $lowLatitude$, $highAltitude$)
in the templates above. The first section describes how these bounds in the templates above. The first section describes how these bounds
are computed in the "resolution encoding" (DHCPv4 GeoConf Option are computed in the "resolution encoding" (DHCPv4 GeoConf
123), while the second section addresses the "uncertainty encoding" Option 123), while the second section addresses the "uncertainty
(DHCPv6 GeoLoc Option TBD2 and DHCPv4 GeoLoc Option TBD1). encoding" (DHCPv6 GeoLoc Option 63 and DHCPv4 GeoLoc Option 144).
A.1.1.1. Resolution Encoding A.1.1.1. Resolution Encoding
Given a number of resolution bits (i.e., the value of a resolution Given a number of resolution bits (i.e., the value of a resolution
field), if all bits beyond those bits are set to zero, this gives the field), if all bits beyond those bits are set to zero, this gives the
lowest possible value. The highest possible value can be found lowest possible value. The highest possible value can be found
setting all bits to one. setting all bits to one.
If the encoded value of Latitude/Longitude and resolution (LaRes, If the encoded value of latitude/longitude and resolution (LaRes,
LoRes) are treated as 34-bit unsigned integers, the following can be LoRes) are treated as 34-bit unsigned integers, the following can be
used (where ">>" is a bitwise right shift, "&" is a bitwise AND, "~" used (where ">>" is a bitwise right shift, "&" is a bitwise AND, "~"
is a bitwise negation, and "|" is a bitwise OR). is a bitwise negation, and "|" is a bitwise OR).
mask = 0x3ffffffff >> resolution mask = 0x3ffffffff >> resolution
lowvalue = value & ~mask lowvalue = value & ~mask
highvalue = value | mask + 1 highvalue = value | mask + 1
Once these values are determined, the corresponding floating point Once these values are determined, the corresponding floating-point
numbers can be computed by dividing the values by 2^25 (since there numbers can be computed by dividing the values by 2^25 (since there
are 25 bits of fraction in the fixed-point representation). are 25 bits of fraction in the fixed-point representation).
Alternatively, the lowest possible value can be found by using Alternatively, the lowest possible value can be found by using
resolution to determine the size of the range. This method has the resolution to determine the size of the range. This method has the
advantage that it operates on the decoded floating point values. It advantage that it operates on the decoded floating-point values. It
is equivalent to the first mechanism, to a possible error of 2^-25 is equivalent to the first mechanism, to a possible error of 2^-25
(2^-8 for altitude). (2^-8 for altitude).
scale = 2 ^ ( 9 - resolution ) scale = 2 ^ ( 9 - resolution )
lowvalue = floor( value / scale ) * scale lowvalue = floor( value / scale ) * scale
highvalue = lowvalue + scale highvalue = lowvalue + scale
Altitude resolution (AltRes) uses the same process with different Altitude resolution (AltRes) uses the same process with different
constants. There are 22 whole bits in the Altitude encoding (instead constants. There are 22 whole bits in the altitude encoding (instead
of 9) and 30 bits in total (instead of 34). of 9) and 30 bits in total (instead of 34).
A.1.1.2. Uncertainty Encoding A.1.1.2. Uncertainty Encoding
In the uncertainty encoding, the uncertainty fields (LongUnc/LatUnc) In the uncertainty encoding, the uncertainty fields (LongUnc/LatUnc)
directly represent the logarithms of uncertainty distances. So the directly represent the logarithms of uncertainty distances. So the
low and high bounds are computed by first computing the uncertainty low and high bounds are computed by first computing the uncertainty
distances, then adding and subtracting these from the value provided. distances, then adding and subtracting these from the value provided.
If "uncertainty" is the unsigned integer value of the uncertainty If "uncertainty" is the unsigned integer value of the uncertainty
field and "value" is the value of the coordinate field: field and "value" is the value of the coordinate field:
distance = 2 ^ (8 - uncertainty) distance = 2 ^ (8 - uncertainty)
lowvalue = value - distance lowvalue = value - distance
highvalue = value + distance highvalue = value + distance
Altitude uncertainty (AltUnc in version 1) uses the same process with Altitude uncertainty (AltUnc in version 1) uses the same process with
different constants: different constants:
distance = 2 ^ (21 - uncertainty) distance = 2 ^ (21 - uncertainty)
lowvalue = value - distance lowvalue = value - distance
Appendix B. Calculations of Resolution Appendix B. Calculations of Resolution
The following examples for two different locations demonstrate how The following examples for two different locations demonstrate how
the Resolution values for Latitude, Longitude, and Altitude (used in the resolution values for latitude, longitude, and altitude (used in
DHCPv4 GeoConf Option 123) can be calculated. In both examples, the DHCPv4 GeoConf Option 123) can be calculated. In both examples, the
geo-location values were derived from maps using the WGS84 map datum, geo-location values were derived from maps using the WGS84 map datum;
therefore in these examples, the Datum field would have a value = 1 therefore, in these examples, the Datum field would have a value = 1
(00000001, or 0x01). (00000001, or 0x01).
B.1. Location Configuration Information of "White House" (Example 1) B.1. Location Configuration Information of "White House" (Example 1)
The grounds of the White House in Washington D.C. (1600 Pennsylvania The grounds of the White House in Washington D.C. (1600 Pennsylvania
Ave. NW, Washington, DC 20006) can be found between 38.895375 and Ave. NW, Washington, DC 20006) can be found between 38.895375 and
38.898653 degrees North and 77.037911 and 77.035116 degrees West. In 38.898653 degrees North and 77.037911 and 77.035116 degrees West. In
this example, we assume that we are standing on the sidewalk on the this example, we assume that we are standing on the sidewalk on the
north side of the White House, between driveways. Since we are not north side of the White House, between driveways. Since we are not
inside a structure, we assume an Altitude value of 15 meters, inside a structure, we assume an altitude value of 15 meters,
interpolated from the US Geological survey map, Washington Washington interpolated from the US Geological survey map, Washington,
West quadrangle. Washington West quadrangle.
The address was NOT picked for any political reason and can easily be The address was NOT picked for any political reason and can easily be
found on the Internet or mapping software, but was picked as an found on the Internet or mapping software, but was picked as an
easily identifiable location on our planet. easily identifiable location on our planet.
In this example, the requirement of emergency responders in North In this example, the requirement of emergency responders in North
America via their NENA Model Legislation [NENA] could be met by a America via their National Emergency Number Association (NENA) Model
LaRes value of 21 and a LoRes value of 20. This would yield a geo- Legislation [NENA] could be met by a LaRes value of 21 and a LoRes
location that is Latitude 38.8984375 north to Latitude 38.8988616 value of 20. This would yield a geo-location that is latitude
north and Longitude -77.0371094 to Longitude -77.0375977. This is an 38.8984375 north to latitude 38.8988616 north and longitude
area of approximately 89 feet by 75 feet or 6669 square feet, which -77.0371094 to longitude -77.0375977. This is an area of
is very close to the 7000 square feet requested by NENA. In this approximately 89 feet by 75 feet or 6669 square feet, which is very
example, a service provider could enforce that a device send a close to the 7000 square feet requested by NENA. In this example, a
Location Configuration Information with this minimum amount of service provider could enforce that a device send location
resolution for this particular location when calling emergency configuration information with this minimum amount of resolution for
services. this particular location when calling emergency services.
An approximate representation of this location might be provided using An approximate representation of this location might be provided
the DHCPv4 GeoConf Option 123 encoding as follows: using the DHCPv4 GeoConf Option 123 encoding as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code (123) | OptLen (16) | LaRes | Latitude . | Code (123) | OptLen (16) | LaRes | Latitude .
|0 1 1 1 1 0 1 1|0 0 0 1 0 0 0 0|0 1 0 0 1 0|0 0 0 1 0 0 1 1 0 1. |0 1 1 1 1 0 1 1|0 0 0 1 0 0 0 0|0 1 0 0 1 0|0 0 0 1 0 0 1 1 0 1.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Latitude (cont'd) | LoRes | . . Latitude (cont'd) | LoRes | .
.1 1 0 0 1 0 1 1 1 0 0 1 1 0 0 0 0 1 1 0 0 0 1 1|0 1 0 0 0 1|1 1. .1 1 0 0 1 0 1 1 1 0 0 1 1 0 0 0 0 1 1 0 0 0 1 1|0 1 0 0 0 1|1 1.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Longitude (cont'd) | . Longitude (cont'd) |
.0 1 1 0 0 1 0 1 1 1 1 0 1 1 0 1 0 1 0 0 0 0 1 0 1 1 0 0 0 1 0 0| .0 1 1 0 0 1 0 1 1 1 1 0 1 1 0 1 0 1 0 0 0 0 1 0 1 1 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AType | AltRes | Altitude . | AType | AltRes | Altitude .
|0 0 0 1|0 1 0 0 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1. |0 0 0 1|0 1 0 0 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Alt (cont'd) | Res |Datum| . Alt (cont'd) | Res |Datum|
.0 0 0 0 0 0 0 0|0 0 0 0 0|0 0 1| .0 0 0 0 0 0 0 0|0 0 0 0 0|0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In hexadecimal, this is 7B10484D CB986347 65ED42C4 1440000F 0001. In hexadecimal, this is 7B10484D CB986347 65ED42C4 1440000F 0001.
Decoding Location Configuration Information with Resolution B.1.1. Decoding Location Configuration Information with Resolution
Decoding this option gives a latitude of 38.897647 (to 7 decimal Decoding this option gives a latitude of 38.897647 (to 7 decimal
places) with 18 bits of resolution; a longitude of -77.0366000 with places) with 18 bits of resolution, a longitude of -77.0366000 with
17 bits of resolution; an altitude type of meters with a value of 15 17 bits of resolution, an Altitude Type of meters with a value of 15
and 17 bits of resolution; version 0 (resolution) and the WGS84 and 17 bits of resolution, version 0 (resolution), and the WGS84
datum. datum.
For the latitude value, 18 bits of resolution allow for values in the For the latitude value, 18 bits of resolution allow for values in the
range from 38.8964844 to 38.8984375. For the longitude value, 17 range from 38.8964844 to 38.8984375. For the longitude value, 17
bits of resolution allow for values in the range from -77.0390625 to bits of resolution allow for values in the range from -77.0390625 to
-77.0351563. Having 17 bits of resolution in the altitude allows for -77.0351563. Having 17 bits of resolution in the altitude allows for
values in the range from 0 to 32 meters. values in the range from 0 to 32 meters.
GML Representation of Decoded Location Configuration Information B.1.2. GML Representation of Decoded Location Configuration Information
The following GML shows the value decoded in the previous example as The following GML shows the value decoded in the previous example as
a point in a three dimensional CRS: a point in a three-dimensional CRS:
<gml:Point srsName="urn:ogc:def:crs:EPSG::4979" <gml:Point srsName="urn:ogc:def:crs:EPSG::4979"
xmlns:gml="http://www.opengis.net/gml"> xmlns:gml="http://www.opengis.net/gml">
<gml:pos>38.897647 -77.0366 15</gml:pos> <gml:pos>38.897647 -77.0366 15</gml:pos>
</gml:Point> </gml:Point>
This representation ignores the values included in the resolution This representation ignores the values included in the resolution
parameters. If resolution values are provided, a rectangular prism parameters. If resolution values are provided, a rectangular prism
can be used to represent the location. can be used to represent the location.
The following example uses all of the decoded information from the The following example uses all of the decoded information from the
previous example: previous example:
<gs:Prism srsName="urn:ogc:def:crs:EPSG::4979" <gs:Prism srsName="urn:ogc:def:crs:EPSG::4979"
xmlns:gs="http://www.opengis.net/pidflo/1.0" xmlns:gs="http://www.opengis.net/pidflo/1.0"
xmlns:gml="http://www.opengis.net/gml"> xmlns:gml="http://www.opengis.net/gml">
<gs:base> <gs:base>
<gml:Polygon> <gml:Polygon>
<gml:exterior> <gml:exterior>
<gml:LinearRing> <gml:LinearRing>
<gml:posList> <gml:posList>
38.8964844 -77.0390625 0 38.8964844 -77.0390625 0
38.8964844 -77.0351563 0 38.8964844 -77.0351563 0
38.8984375 -77.0351563 0 38.8984375 -77.0351563 0
38.8984375 -77.0390625 0 38.8984375 -77.0390625 0
38.8964844 -77.0390625 0 38.8964844 -77.0390625 0
</gml:posList> </gml:posList>
</gml:LinearRing> </gml:LinearRing>
</gml:exterior>
</gml:exterior> </gml:Polygon>
</gml:Polygon> </gs:base>
</gs:base> <gs:height uom="urn:ogc:def:uom:EPSG::9001">
<gs:height uom="urn:ogc:def:uom:EPSG::9001"> 32
32 </gs:height>
</gs:height> </gs:Prism>
</gs:Prism>
B.2. Location Configuration Information of "Sears Tower" (Example 2) B.2. Location Configuration Information of "Sears Tower" (Example 2)
Postal Address: Postal Address:
Sears Tower Sears Tower
103rd Floor 103rd Floor
233 S. Wacker Dr. 233 S. Wacker Dr.
Chicago, IL 60606 Chicago, IL 60606
Viewing the Chicago area from the Observation Deck of the Sears Viewing the Chicago area from the Observation Deck of the Sears
Tower. Tower:
Latitude 41.87884 degrees North (or +41.87884 degrees) Latitude 41.87884 degrees North (or +41.87884 degrees)
Using 2s complement, 34 bit fixed point, 25 bit fraction Using two's complement, 34-bit fixed point, 25 bits of fraction
Latitude = 0x053c1f751, Latitude = 0x053c1f751,
Latitude = 0001010011110000011111011101010001 Latitude = 0001010011110000011111011101010001
Longitude 87.63602 degrees West (or -87.63602 degrees) Longitude 87.63602 degrees West (or -87.63602 degrees)
Using 2s complement, 34 bit fixed point, 25 bit fraction Using two's complement, 34-bit fixed point, 25 bits of fraction
Longitude = 0xf50ba5b97, Longitude = 0xf50ba5b97,
Longitude = 1101010000101110100101101110010111 Longitude = 1101010000101110100101101110010111
Altitude 103 Altitude 103
In this example, we are inside a structure, therefore we will assume In this example, we are inside a structure; therefore, we will assume
an Altitude value of 103 to indicate the floor we are on. The an altitude value of 103 to indicate the floor we are on. The
Altitude Type value is 2, indicating floors. The AltRes field would Altitude Type value is 2, indicating floors. The AltRes field would
indicate that all bits in the Altitude field are true, as we want to indicate that all bits in the Altitude field are true, as we want to
accurately represent the floor of the structure where we are located. accurately represent the floor of the structure where we are located.
AltRes = 30, 0x1e, 011110 AltRes = 30, 0x1e, 011110
AType = 2, 0x02, 000010 AType = 2, 0x02, 000010
Altitude = 103, 0x00006700, 000000000000000110011100000000 Altitude = 103, 0x00006700, 000000000000000110011100000000
For the accuracy of the Latitude and Longitude, the best information For the accuracy of the latitude and longitude, the best information
available to us was supplied by a generic mapping service that shows available to us was supplied by a generic mapping service that shows
a single geo-loc for all of the Sears Tower. Therefore we are going a single geo-loc for all of the Sears Tower. Therefore, we are going
to show LaRes as value 18 (0x12 or 010010) and LoRes as value 18 to show LaRes as value 18 (0x12 or 010010) and LoRes as value 18
(0x12 or 010010). This would be describing a geo-location area that (0x12 or 010010). This would be describing a geo-location area that
is Latitude 41.8769531 to Latitude 41.8789062 and extends from is latitude 41.8769531 to latitude 41.8789062 and extends from
-87.6367188 degrees to -87.6347657 degrees Longitude. This is an -87.6367188 degrees to -87.6347657 degrees longitude. This is an
area of approximately 373412 square feet (713.3 ft. x 523.5 ft.). area of approximately 373412 square feet (713.3 ft. x 523.5 ft.).
Appendix C. Calculations of Uncertainty Appendix C. Calculations of Uncertainty
The following example demonstrates how uncertainty values for The following example demonstrates how uncertainty values for
Latitude, Longitude, and Altitude (LatUnc, LongUnc and AltUnc latitude, longitude, and altitude (LatUnc, LongUnc, and AltUnc used
used in the DHCPv6 GeoLoc Option TBD2 as well as DHCPv4 GeoLoc in the DHCPv6 GeoLoc Option 63 as well as DHCPv4 GeoLoc Option 144)
Option TBD1) can be calculated. can be calculated.
C.1. Location Configuration Information of "Sydney Opera House" C.1. Location Configuration Information of "Sydney Opera House"
(Example 3) (Example 3)
This section describes an example of encoding and decoding the This section describes an example of encoding and decoding the
geodetic DHCP Option. The textual results are expressed in GML geodetic DHCP Option. The textual results are expressed in GML
[OGC.GML-3.1.1] form, suitable for inclusion in PIDF-LO [RFC4119]. [OGC-GML3.1.1] form, suitable for inclusion in PIDF-LO [RFC4119].
These examples all assume a datum of WGS84 (datum = 1) and an These examples all assume a datum of WGS84 (datum = 1) and an
Altitude type of meters (AType = 1). Altitude Type of meters (AType = 1).
C.1.1. Encoding a Location into DHCP Geodetic Form C.1.1. Encoding a Location into DHCP Geodetic Form
This example draws a rough polygon around the Sydney Opera House. This example draws a rough polygon around the Sydney Opera House.
This polygon consists of the following six points: This polygon consists of the following six points:
33.856625 S, 151.215906 E 33.856625 S, 151.215906 E
33.856299 S, 151.215343 E 33.856299 S, 151.215343 E
33.856326 S, 151.214731 E 33.856326 S, 151.214731 E
33.857533 S, 151.214495 E 33.857533 S, 151.214495 E
33.857720 S, 151.214613 E 33.857720 S, 151.214613 E
33.857369 S, 151.215375 E 33.857369 S, 151.215375 E
The top of the building 67.4 meters above sea level, and a starting The top of the building is 67.4 meters above sea level, and a
Altitude of 0 meters above the WGS84 geoid is assumed. starting altitude of 0 meters above the WGS84 geoid is assumed.
The first step is to determine the range of Latitude and Longitude The first step is to determine the range of latitude and longitude
values. Latitude ranges from -33.857720 to -33.856299; Longitude values. Latitude ranges from -33.857720 to -33.856299; longitude
ranges from 151.214495 to 151.215906. ranges from 151.214495 to 151.215906.
For this example, the point that is encoded is chosen by finding the For this example, the point that is encoded is chosen by finding the
middle of each range, that is (-33.8570095, 151.2152005). This is middle of each range, that is (-33.8570095, 151.2152005). This is
encoded as (1110111100010010010011011000001101, encoded as (1110111100010010010011011000001101,
0100101110011011100010111011000011) in binary, or (3BC49360D, 0100101110011011100010111011000011) in binary, or (3BC49360D,
12E6E2EC3) in hexadecimal notation (with an extra 2 bits of leading 12E6E2EC3) in hexadecimal notation (with an extra 2 bits of leading
padding on each). Altitude is set at 33.7 meters, which is padding on each). Altitude is set at 33.7 meters, which is
000000000000000010000110110011 (binary) or 000021B3 (hexadecimal). 000000000000000010000110110011 (binary) or 000021B3 (hexadecimal).
The Latitude Uncertainty (LatUnc) is given by inserting the The latitude uncertainty (LatUnc) is given by inserting the
difference between the center value and the outer value into the difference between the center value and the outer value into the
formula from Section 2.3.1. This gives: formula from Section 2.3.2. This gives:
x = 8 - ceil( log2( -33.8570095 - -33.857720 ) ) x = 8 - ceil( log2( -33.8570095 - -33.857720 ) )
The result of this equation is 18, therefore the uncertainty is The result of this equation is 18; therefore, the uncertainty is
encoded as 010010 in binary. encoded as 010010 in binary.
Similarly, Longitude Uncertainty (LongUnc) is given by the formula: Similarly, longitude uncertainty (LongUnc) is given by the formula:
x = 8 - ceil( log2( 151.2152005 - 151.214495 ) ) x = 8 - ceil( log2( 151.2152005 - 151.214495 ) )
The result of this equation is also 18, or 010010 in binary. The result of this equation is also 18, or 010010 in binary.
Altitude Uncertainty (AltUnc) uses the formula from Section 2.4.4: Altitude uncertainty (AltUnc) uses the formula from Section 2.4.5:
x = 21 - ceil( log2( 33.7 - 0 ) ) x = 21 - ceil( log2( 33.7 - 0 ) )
The result of this equation is 15, which is encoded as 001111 in The result of this equation is 15, which is encoded as 001111 in
binary. binary.
Adding an Altitude Type of 1 (meters) and a Datum of 1 (WGS84), this Adding an Altitude Type of 1 (meters) and a Datum of 1 (WGS84), this
gives the following DHCPv4 GeoLoc Option TBD1 form: gives the following DHCPv4 GeoLoc Option 144 form:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code (TBD1) | OptLen (16) | LatUnc | Latitude . | Code (144) | OptLen (16) | LatUnc | Latitude .
|0 1 1 1 1 0 1 1|0 0 0 1 0 0 0 0|0 1 0 0 1 0|1 1 1 0 1 1 1 1 0 0. |0 1 1 1 1 0 1 1|0 0 0 1 0 0 0 0|0 1 0 0 1 0|1 1 1 0 1 1 1 1 0 0.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Latitude (cont'd) | LongUnc | . . Latitude (cont'd) | LongUnc | .
.0 1 0 0 1 0 0 1 0 0 1 1 0 1 1 0 0 0 0 0 1 1 0 1|0 1 0 0 1 0|0 1. .0 1 0 0 1 0 0 1 0 0 1 1 0 1 1 0 0 0 0 0 1 1 0 1|0 1 0 0 1 0|0 1.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Longitude (cont'd) | . Longitude (cont'd) |
.0 0 1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 0 1 0 1 1 1 0 1 1 0 0 0 0 1 1| .0 0 1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 0 1 0 1 1 1 0 1 1 0 0 0 0 1 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AType | AltUnc | Altitude . | AType | AltUnc | Altitude .
|0 0 0 1|0 0 1 1 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1. |0 0 0 1|0 0 1 1 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Alt (cont'd) |Ver| Res |Datum| . Alt (cont'd) |Ver| Res |Datum|
.1 0 1 1 0 0 1 1|0 1|0 0 0|0 0 1| .1 0 1 1 0 0 1 1|0 1|0 0 0|0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In hexadecimal, this is 7B104BBC 49360D49 2E6E2EC3 13C00021 B341. In hexadecimal, this is 7B104BBC 49360D49 2E6E2EC3 13C00021 B341.
The DHCPv6 form only differs in the code and option length portion. The DHCPv6 form only differs in the code and option length portion.
C.1.2. Decoding a Location from DHCP Geodetic Form C.1.2. Decoding a Location from DHCP Geodetic Form
If receiving the binary form created in the previous section, this If receiving the binary form created in the previous section, this
section describes how that would be interpreted. The result is then section describes how that would be interpreted. The result is then
represented as a GML object, as defined in [GeoShape]. represented as a GML object, as defined in [GeoShape].
A Latitude value of 1110111100010010010011011000001101 decodes to a A latitude value of 1110111100010010010011011000001101 decodes to a
value of -33.8570095003 (to 10 decimal places). The Longitude value value of -33.8570095003 (to 10 decimal places). The longitude value
of 0100101110011011100010111011000011 decodes to 151.2152005136. of 0100101110011011100010111011000011 decodes to 151.2152005136.
Decoding Tip: If the raw values of Latitude and Longitude are placed Decoding Tip: If the raw values of latitude and longitude are placed
in integer variables, the actual value can be derived by the in integer variables, the actual value can be derived by the
following process: following process:
1. If the highest order bit is set (i.e. the number is a twos 1. If the highest order bit is set (i.e., the number is a two's
complement negative), then subtract 2 to the power of 34 (the complement negative), then subtract 2 to the power of 34 (the
total number of bits). total number of bits).
2. Divide the result by 2 to the power of 25 (the number of 2. Divide the result by 2 to the power of 25 (the number of
fractional bits) to determine the final value. fractional bits) to determine the final value.
The same principle can be applied when decoding Altitude values, The same principle can be applied when decoding altitude values,
except with different powers of 2 (30 and 8 respectively). except with different powers of 2 (30 and 8, respectively).
The Latitude and Longitude Uncertainty are both 18, which gives an The latitude and longitude uncertainty are both 18, which gives an
uncertainty value using the formula from Section 2.3.1 of uncertainty value of 0.0009765625 using the formula from
0.0009765625. Therefore, the decoded Latitudes is -33.8570095003 +/- Section 2.3.2. Therefore, the decoded latitude is -33.8570095003 +/-
0.0009765625 (or the range from -33.8579860628 to -33.8560329378) and 0.0009765625 (or the range from -33.8579860628 to -33.8560329378) and
the decoded Longitude is 151.2152005136 +/- 0.0009765625 (or the the decoded longitude is 151.2152005136 +/- 0.0009765625 (or the
range from 151.2142239511 to 151.2161770761). range from 151.2142239511 to 151.2161770761).
The encoded Altitude of 000000000000000010000110110011 decodes to The encoded altitude of 000000000000000010000110110011 decodes to
33.69921875. The encoded uncertainty of 15 gives a value of 64, 33.69921875. The encoded uncertainty of 15 gives a value of 64;
therefore the final uncertainty is 33.69921875 +/- 64 (or the range therefore, the final uncertainty is 33.69921875 +/- 64 (or the range
from -30.30078125 to 97.69921875). from -30.30078125 to 97.69921875).
C.1.2.1. GML Representation of Decoded Locations C.1.2.1. GML Representation of Decoded Locations
The following GML shows the value decoded in the previous example as The following GML shows the value decoded in the previous example as
a point in a three dimensional CRS: a point in a three-dimensional CRS:
<gml:Point srsName="urn:ogc:def:crs:EPSG::4979" <gml:Point srsName="urn:ogc:def:crs:EPSG::4979"
xmlns:gml="http://www.opengis.net/gml"> xmlns:gml="http://www.opengis.net/gml">
<gml:pos>-33.8570095003 151.2152005136 33.69921875</gml:pos> <gml:pos>-33.8570095003 151.2152005136 33.69921875</gml:pos>
</gml:Point> </gml:Point>
The following example uses all of the decoded information from the The following example uses all of the decoded information from the
previous example: previous example:
<gs:Prism srsName="urn:ogc:def:crs:EPSG::4979" <gs:Prism srsName="urn:ogc:def:crs:EPSG::4979"
xmlns:gs="http://www.opengis.net/pidflo/1.0" xmlns:gs="http://www.opengis.net/pidflo/1.0"
xmlns:gml="http://www.opengis.net/gml"> xmlns:gml="http://www.opengis.net/gml">
<gs:base> <gs:base>
<gml:Polygon> <gml:Polygon>
<gml:exterior> <gml:exterior>
<gml:LinearRing> <gml:LinearRing>
<gml:posList> <gml:posList>
-33.8579860628 151.2142239511 -30.30078125 -33.8579860628 151.2142239511 -30.30078125
-33.8579860628 151.2161770761 -30.30078125 -33.8579860628 151.2161770761 -30.30078125
-33.8560329378 151.2161770761 -30.30078125 -33.8560329378 151.2161770761 -30.30078125
-33.8560329378 151.2142239511 -30.30078125 -33.8560329378 151.2142239511 -30.30078125
-33.8579860628 151.2142239511 -30.30078125 -33.8579860628 151.2142239511 -30.30078125
</gml:posList> </gml:posList>
</gml:LinearRing> </gml:LinearRing>
</gml:exterior> </gml:exterior>
</gml:Polygon> </gml:Polygon>
</gs:base> </gs:base>
<gs:height uom="urn:ogc:def:uom:EPSG::9001"> <gs:height uom="urn:ogc:def:uom:EPSG::9001">
128 128
</gs:height> </gs:height>
</gs:Prism> </gs:Prism>
Note that this representation is only appropriate if the uncertainty Note that this representation is only appropriate if the uncertainty
is sufficiently small. [GeoShape] recommends that distances between is sufficiently small. [GeoShape] recommends that distances between
polygon vertices be kept short. A GML representation like this one polygon vertices be kept short. A GML representation like this one
is only appropriate where uncertainty is less than 1 degree (an is only appropriate where uncertainty is less than 1 degree (an
encoded value of 9 or greater). encoded value of 9 or greater).
Appendix D. Changes from RFC 3825 Appendix D. Changes from RFC 3825
This section lists the major changes between RFC 3825 and this This section lists the major changes between RFC 3825 and this
document. Minor changes, including style, grammar, spelling and document. Minor changes, including style, grammar, spelling, and
editorial changes are not mentioned here. editorial changes, are not mentioned here.
o Section 1 now includes clarifications on wired and wireless uses. o Section 1 now includes clarifications on wired and wireless uses.
o The former Sections 1.2 and 1.3 have been removed. Section 1.2 o The former Sections 1.2 and 1.3 have been removed. Section 1.2
now defines the concepts of uncertainty and resolution, as well now defines the concepts of uncertainty and resolution, as well as
as conversion between the DHCP option formats and PIDF-LO. conversion between the DHCP option formats and PIDF-LO.
o A DHCPv6 GeoLoc Option is now defined (Section 2.1) as well
as a new DHCPv4 GeoLoc Option (Section 2.2.2). o A DHCPv6 GeoLoc Option is now defined (Section 2.1) as well as a
o The former Datum field has been split into three fields: new DHCPv4 GeoLoc Option (Section 2.2.2).
Ver, Res and Datum. These fields are used in both the
DHCPv4 GeoLoc Option and the DHCPv6 GeoLoc Option. o The former Datum field has been split into three fields: Ver, Res,
and Datum. These fields are used in both the DHCPv4 GeoLoc Option
and the DHCPv6 GeoLoc Option.
o Section 2.2.3 has been added, describing option support o Section 2.2.3 has been added, describing option support
requirements on DHCP clients and servers. requirements on DHCP clients and servers.
o Section 2.3 has been added, describing the Latitude and
Longitude fields. o Section 2.3 has been added, describing the Latitude and Longitude
o Section 2.3.1 has been added, covering Latitude and Longitude fields.
o Section 2.3.1 has been added, covering latitude and longitude
resolution. resolution.
o Section 2.3.2 has been added, covering Latitude and Longitude
o Section 2.3.2 has been added, covering latitude and longitude
uncertainty. uncertainty.
o Section 2.4 has been added, covering values of the Altitude
field (Sections 2.4.1, 2.4.2 and 2.4.3), Altitude resolution o Section 2.4 has been added, covering values of the Altitude field
(Section 2.4.4), and Altitude uncertainty (Section 2.4.5). (Sections 2.4.1, 2.4.2, and 2.4.3), altitude resolution
(Section 2.4.4), and altitude uncertainty (Section 2.4.5).
o Section 2.5 has been added, covering the Datum field. o Section 2.5 has been added, covering the Datum field.
o Section 3 (Security Considerations) has added a recommendation
on link layer confidentiality. o Section 3 (Security Considerations) has added a recommendation on
o Section 4 (IANA Considerations) has consolidated material link-layer confidentiality.
relating to parameter allocation for both the DHCPv4 and
DHCPv6 option parameters, and has been rewritten to o Section 4 (IANA Considerations) has consolidated material relating
conform to the practices recommended in RFC 5226. to parameter allocation for both the DHCPv4 and DHCPv6 option
o The material formerly in Appendix A has been updated and parameters, and has been rewritten to conform to the practices
shortened and has been moved to Appendix B. recommended in RFC 5226.
o The material formerly in Appendix A has been updated and shortened
and has been moved to Appendix B.
o An Appendix A on GML mapping has been added. o An Appendix A on GML mapping has been added.
o Appendix C has been added, providing an example of uncertainty o Appendix C has been added, providing an example of uncertainty
encoding. encoding.
o Appendix D has been added, detailing the changes from RFC 3825. o Appendix D has been added, detailing the changes from RFC 3825.
Authors' Addresses Authors' Addresses
James M. Polk James M. Polk
Cisco Systems Cisco Systems
2200 East President George Bush Turnpike 2200 East President George Bush Turnpike
Richardson, Texas 75082 USA Richardson, TX 75082
USA USA
EMail: jmpolk@cisco.com EMail: jmpolk@cisco.com
Marc Linsner Marc Linsner
Cisco Systems Cisco Systems
Marco Island, FL 34145 USA Marco Island, FL 34145
USA USA
EMail: marc.linsner@cisco.com EMail: marc.linsner@cisco.com
Martin Thomson Martin Thomson
Andrew Corporation Andrew Corporation
PO Box U40 PO Box U40
Wollongong University Campus, NSW 2500 Wollongong University Campus, NSW 2500
AU AU
EMail: martin.thomson@andrew.com EMail: martin.thomson@andrew.com
Bernard Aboba Bernard Aboba (editor)
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052 USA Redmond, WA 98052
USA USA
EMail: bernard_aboba@hotmail.com EMail: bernard_aboba@hotmail.com
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