GeoPriv M. Linsner
Internet Draft Cisco Systems
Intended status: Standards Track A. Thomson
Expires: December 27, 2007 Cisco Systems
June 26, 2007
Relative Location for Civic Location Format
draft-linsner-geopriv-relativeloc-01.txt
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Copyright (C) The IETF Trust (2007).
Abstract
This document defines additional civic address parameters for use in
Location Objects [1] and [4]. The format is based on the civic
address definition of PIDF-LO. These additional parameters allow
expression of a relative location.
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Conventions used in this document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [1].
Table of Contents
1. Introduction...................................................2
2. Additions to PIDF-LO...........................................3
3. Additions to DHCP Civic Location Option........................3
4. Relative Location..............................................3
4.1. Examples of the relative location parameters..............5
5. Example Schema.................................................6
6. Security Considerations........................................6
7. IANA Considerations............................................7
7.1. XML Schema Registration...................................7
7.2. CAType Registry Update....................................7
8. Acknowledgments................................................7
9. References.....................................................8
9.1. Normative References......................................8
9.2. Informative References....................................8
Author's Addresses................................................8
Intellectual Property Statement...................................8
Disclaimer of Validity............................................9
1. Introduction
Wireless LAN technologies are adding capabilities to locate serving
hosts via radio frequency measurement technologies. This new
capability is able to provide additional and more accurate location
information when used inside a building, or on a campus in
conjunction with civic addressing. The data produced from these
technologies is most useful if expressed as relative position.
Relative position dictates the expression of an anchor point, or
starting point for measurement, hence providing both the relative
position and relative location offset from the relative position is
provided.
The data included within the relative position parameters is
supplementary to, not exclusive of, the existing civic location data
expressed in PIDF-LO [1] and DHCP Civic Location option [4]. An
example of this may be a popular wireless hotspot located at 234 N.
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Main St. It is reasonable to expect that 234 N. Main St. covers a
geographic area that encompasses several hundred square meters. The
wireless network architecture for this hotspot could include several
wireless infrastructure access points. The supplementary data
provided via relative location would enable a more granular location
expression. In addition to providing 234 N. Main St., a relative
position like "20 feet south and 40 feet east of the main entrance"
could be added.
It is expected this supplementary civic location data will be used
within the confines of the associated civic location and SHOULD not
be used to represent locations that are off-campus, or outside the
boundary of the expressed civic address. In other words, using the
cited example, providing a street address of 234 N. Main St. and then
provide this relative location data that result in the location
residing at another street address SHOULD not be allowed.
Although [1] and [4] currently supports additional elements, like
CAtypes 28 (room), 32 (additional code), or 33 (seat), results from
the radio frequency measurement technologies are alternatives to
these existing elements and in some cases the resultant location can
be more accurate.
2. Additions to PIDF-LO
PIDF-LO, as updated by [2], includes a full set of parameters used to
describe civic locations. The new parameters defined here are
additional to the updated set and provide a means to describe a
host's civic location with added granularity.
3. Additions to DHCP Civic Location Option
The new parameters defined here are additional and will update DHCP
Civic Location Option [4]
4. Relative Location
Relative location is defined by 2 new parameters, reference point and
relative position. Reference point, similar to geodetic datum,
defines the anchor point (0,0 point) used for measurement of the
relative position parameter. Measurement from the anchor point is
provided in 3 dimensions, X, Y and Z. The east-west dimension is
labeled X and north-south dimension is labeled Y. A positive Y value
is considered north of the reference point, a negative Y value south
of the reference point, a positive X value for east of the reference
point and a negative X value for west of the reference point. An
additional value in this relative position parameter defines the unit
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of measure (UoM). Lack of expressing a measurement unit defaults the
unit value to meters.
The fourth, height or altitude parameter (Z) found in normal geodetic
systems can be optionally expressed via these new parameters but
might be more useful converted to floor values and expressed in via
CAtype 27, the FLR or Floor parameter, previously defined for [1] and
[4]. If the altitude (Z) parameter is expressed, it is assumed to
utilize locally significant ground level (the ground directly below
the relative location) as the reference point from which to measure.
To provide the most accurate location and due to the uniqueness of
earth curvature with respect to perpendicular lines, the east-west
measurement SHOULD be calculated/plotted first, followed by the
north-south value.
For this usage, defining the reference point of local significance is
completely subjective, but utilizing intuitively obviously locations,
like 'Elevator', 'Exit Door', 'Stairwell', etc. is suggested.
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New Civic CAtype Description Example
Field
REFPT 40 Reference Point Elevator
RELPOS-X 41 Relative Position X <X>-12</X>
RELPOS-Y 42 Relative Position Y <Y>35</Y>
RELPOS-Z 43 Relative Position Z <Z>60</Z>
optional
RELPOS-UOW 44 Units of measurement for <UoW>feet</UoW>
relative position
Optional,
default value
meters.
Table 1: New Civic CAtypes
4.1. Examples of the relative location parameters
A location that is 20 meters west and 31 meters south of elevator-1
<REFPT>elevator-1</REFPT>
<RELPOS-X>-20</RELPOS-X>
<RELPOS-Y>-31</RELPOS-Y>
A location that is 51 feet north and 23 feet east of the corner
office
<REFPT>corner_office</REFPT>
<RELPOS-X>23</RELPOS-X>
<RELPOS-Y>51</RELPOS-Y>
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<RELPOS-UOM>feet</RELPOS-UOM>
5. Example Schema
<xs:schema targetNamespace="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:xml="http://www.w3.org/XML/1998/namespace"
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:import namespace="http://www.w3.org/XML/1998/namespace"
schemaLocation="http://www.w3.org/2001/xml.xsd" />
<xs:element name="civicAddress" type="ca:civicAddress" />
<xs:complexType name="caType">
<xs:simpleContent>
<xs:extension base="xs:token">
<xs:attribute ref="xml:lang" use="optional" />
</xs:extension>
</xs:simpleContent>
</xs:complexType>
<xs:complexType name="civicAddress">
<xs:sequence>
<!-- additions to civicAddress -->
<xs:element name="refpt" type="ca:caType" minOccurs="0" />
<xs:element name="relpos-x" type="ca:caType" minOccurs="0" />
<xs:element name="relpos-y" type="ca:caType" minOccurs="0" />
<xs:element name="relpos-z" type="ca:caType" minOccurs="0" />
<xs:element name="relpos-uom" type="ca:UoM" minOccurs="0" />
</xs:sequence>
</xs:complexType>
<xs:simpleType name="UoM">
<xs:restriction base="ca:caType">
<xs:enumeration value="feet" />
<xs:enumeration value="meters" />
</xs:restriction>
</xs:simpleType>
</xs:schema>
6. Security Considerations
The XML parameters defined in the document are additions to the
current PIDF-LO specification. Therefore the parameters defined here
are subject to the same security considerations of [1].
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7. IANA Considerations
7.1. XML Schema Registration
IANA will update the registered XML schema with additions as shown in
section 5. of this document.
URI: urn:ietf:params:xml:schema:pidf:geopriv10:civicAddr
7.2. CAType Registry Update
IANA will update the civic address type registry established by
RFC4776. The additions to the registry are shown in Table 1 of the
document.
8. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
The authors would like to thank Martin Thomson and Carl Reed for
their contributions to this draft.
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9. References
9.1. Normative References
[1] Petersen, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005.
[2] Thomson, M. & Winterbottom, J., "Revised Civic Location Format
for PIDF-LO", draft-ietf-geopriv-revised-civic-lo-05.txt,
February 2007.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[4] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4
and DHCPv6) Option for Civic Addresses Configuration
Information", RFC4776, November 2006
9.2. Informative References
Author's Addresses
Marc Linsner
Cisco Systems, Inc.
Marco Island, Florida, USA
Email: mlinsner@cisco.com
Allan Thomson
Cisco Systems, Inc.
San Jose, California, USA
Email: althomso@cisco.com
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Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Martin Thomson and Carl Reed made significant contributions to both
the usage and technical aspects of the relative location addition to
civic locations.
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