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diff --git a/doc/rfc/rfc5491.txt b/doc/rfc/rfc5491.txt new file mode 100644 index 0000000..ebd1844 --- /dev/null +++ b/doc/rfc/rfc5491.txt @@ -0,0 +1,1571 @@ + + + + + + +Network Working Group J. Winterbottom +Request for Comments: 5491 M. Thomson +Updates: 4119 Andrew Corporation +Category: Standards Track H. Tschofenig + Nokia Siemens Networks + March 2009 + + + GEOPRIV Presence Information Data Format Location Object (PIDF-LO) + Usage Clarification, Considerations, and Recommendations + +Status of This Memo + + This document specifies an Internet standards track protocol for the + Internet community, and requests discussion and suggestions for + improvements. Please refer to the current edition of the "Internet + Official Protocol Standards" (STD 1) for the standardization state + and status of this protocol. Distribution of this memo is unlimited. + +Copyright Notice + + Copyright (c) 2009 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents in effect on the date of + publication of this document (http://trustee.ietf.org/license-info). + Please review these documents carefully, as they describe your rights + and restrictions with respect to this document. + + + + + + + + + + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 1] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +Abstract + + The Presence Information Data Format Location Object (PIDF-LO) + specification provides a flexible and versatile means to represent + location information. There are, however, circumstances that arise + when information needs to be constrained in how it is represented. + In these circumstances, the range of options that need to be + implemented are reduced. There is growing interest in being able to + use location information contained in a PIDF-LO for routing + applications. To allow successful interoperability between + applications, location information needs to be normative and more + tightly constrained than is currently specified in RFC 4119 (PIDF- + LO). This document makes recommendations on how to constrain, + represent, and interpret locations in a PIDF-LO. It further + recommends a subset of Geography Markup Language (GML) 3.1.1 that is + mandatory to implement by applications involved in location-based + routing. + +Table of Contents + + 1. Introduction ....................................................3 + 2. Terminology .....................................................3 + 3. Using Location Information ......................................4 + 3.1. Single Civic Location Information ..........................7 + 3.2. Civic and Geospatial Location Information ..................7 + 3.3. Manual/Automatic Configuration of Location Information .....8 + 3.4. Multiple Location Objects in a Single PIDF-LO ..............9 + 4. Geodetic Coordinate Representation .............................10 + 5. Geodetic Shape Representation ..................................10 + 5.1. Polygon Restrictions ......................................12 + 5.2. Shape Examples ............................................13 + 5.2.1. Point ..............................................13 + 5.2.2. Polygon ............................................14 + 5.2.3. Circle .............................................17 + 5.2.4. Ellipse ............................................17 + 5.2.5. Arc Band ...........................................19 + 5.2.6. Sphere .............................................21 + 5.2.7. Ellipsoid ..........................................22 + 5.2.8. Prism ..............................................24 + 6. Security Considerations ........................................26 + 7. Acknowledgments ................................................26 + 8. References .....................................................26 + 8.1. Normative References ......................................26 + 8.2. Informative References ....................................27 + + + + + + + +Winterbottom, et al. Standards Track [Page 2] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +1. Introduction + + The Presence Information Data Format Location Object (PIDF-LO) + [RFC4119] is the recommended way of encoding location information and + associated privacy policies. Location information in a PIDF-LO may + be described in a geospatial manner based on a subset of Geography + Markup Language (GML) 3.1.1 [OGC-GML3.1.1] or as civic location + information [RFC5139]. A GML profile for expressing geodetic shapes + in a PIDF-LO is described in [GeoShape]. Uses for the PIDF-LO are + envisioned in the context of numerous location-based applications. + This document makes recommendations for formats and conventions to + make interoperability less problematic. + + The PIDF-LO provides a general presence format for representing + location information, and permits specification of location + information relating to a whole range of aspects of a Target. The + general presence data model is described in [RFC4479] and caters to a + presence document to describe different aspects of the reachability + of a presentity. Continuing this approach, a presence document may + contain several GEOPRIV objects that specify different locations and + aspects of reachability relating to a presentity. This degree of + flexibility is important, and recommendations in this document make + no attempt to forbid the usage of a PIDF-LO in this manner. This + document provides a specific set of guidelines for building presence + documents when it is important to unambiguously convey exactly one + location. + +2. Terminology + + 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 [RFC2119]. + + The definition for "Target" is taken from [RFC3693]. + + In this document a "discrete location" is defined as a place, point, + area, or volume in which a Target can be found. + + The term "compound location" is used to describe location information + represented by a composite of both civic and geodetic information. + An example of compound location might be a geodetic polygon + describing the perimeter of a building and a civic element + representing the floor in the building. + + The term "method" in this document refers to the mechanism used to + determine the location of a Target. This may be something employed + by a location information server (LIS), or by the Target itself. It + + + + +Winterbottom, et al. Standards Track [Page 3] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + specifically does not refer to the location configuration protocol + (LCP) used to deliver location information either to the Target or + the Recipient. + + The term "source" is used to refer to the LIS, node, or device from + which a Recipient (Target or Third-Party) obtains location + information. + +3. Using Location Information + + The PIDF format provides for an unbounded number of <tuple>, + <device>, and <person> elements. Each of these elements contains a + single <status> element that may contain more than one <geopriv> + element as a child. Each <geopriv> element must contain at least the + following two child elements: <location-info> element and <usage- + rules> element. One or more elements containing location information + are contained inside a <location-info> element. + + Hence, a single PIDF document may contain an arbitrary number of + location objects, some or all of which may be contradictory or + complementary. Graphically, the structure of a PIDF-LO document can + be depicted as shown in Figure 1. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 4] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + <presence> + <tuple> -- #1 + <status> + <geopriv> -- #1 + <location-info> + location element #1 + location element #2 + ... + location element #n + <usage-rules> + </geopriv> + <geopriv> -- #2 + <geopriv> -- #3 + ... + <geopriv> -- #m + </status> + </tuple> + <device> + <geopriv> -- #1 + <location-info> + location element(s) + <usage-rules> + </geopriv> + <geopriv> -- #2 + ... + <geopriv> -- #m + </device> + <person> + <geopriv> -- #1 + <location-info> + location element(s) + <usage-rules> + </geopriv> + <geopriv> -- #2 + ... + <geopriv> -- #m + </person> + <tuple> -- #2 + <device> -- #2 + <person> -- #2 + ... + <tuple> -- #o + </presence> + + Figure 1: Structure of a PIDF-LO Document + + + + + + +Winterbottom, et al. Standards Track [Page 5] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + All of these potential sources and storage places for location lead + to confusion for the generators, conveyors, and consumers of location + information. Practical experience within the United States National + Emergency Number Association (NENA) in trying to solve these + ambiguities led to a set of conventions being adopted. These rules + do not have any particular order, but should be followed by creators + and consumers of location information contained in a PIDF-LO to + ensure that a consistent interpretation of the data can be achieved. + + Rule #1: A <geopriv> element MUST describe a discrete location. + + Rule #2: Where a discrete location can be uniquely described in more + than one way, each location description SHOULD reside in a + separate <tuple>, <device>, or <person> element; only one geopriv + element per tuple. + + Rule #3: Providing more than one <geopriv> element in a single + presence document (PIDF) MUST only be done if the locations refer + to the same place or are put into different element types. For + example, one location in a <tuple>, a second location in a + <device> element, and a third location in a <person> element. + + This may occur if a Target's location is determined using a + series of different techniques or if the Target wishes to + represent her location as well as the location of her PC. In + general, avoid putting more than one location into a document + unless it makes sense to do so. + + Rule #4: Providing more than one location chunk in a single + <location-info> element SHOULD be avoided where possible. Rule #5 + and Rule #6 provide further refinement. + + Rule #5: When providing more than one location chunk in a single + <location-info> element, the locations MUST be provided by a + common source at the same time and by the same location + determination method. + + Rule #6: Providing more than one location chunk in a single + <location-info> element SHOULD only be used for representing + compound location referring to the same place. + + For example, a geodetic location describing a point, and a + civic location indicating the floor in a building. + + + + + + + + +Winterbottom, et al. Standards Track [Page 6] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + Rule #7: Where the compound location is provided in a single + <location-info> element, the coarse location information MUST be + provided first. + + For example, a geodetic location describing an area and a civic + location indicating the floor should be represented with the + area first followed by the civic location. + + Rule #8: Where a PIDF document contains more than one <geopriv> + element, the priority of interpretation is given to the first + <device> element in the document containing a location. If no + <device> element containing a location is present in the document, + then priority is given to the first <tuple> element containing a + location. Locations contained in <person> tuples SHOULD only be + used as a last resort. + + Rule #9: Where multiple PIDF documents can be sent or received + together, say in a multi-part MIME body, and current location + information is required by the recipient, then document selection + SHOULD be based on document order, with the first document + considered first. + + The following examples illustrate the application of these rules. + +3.1. Single Civic Location Information + + Jane is at a coffee shop on the ground floor of a large shopping + mall. Jane turns on her laptop and connects to the coffee shop's + WiFi hotspot; Jane obtains a complete civic address for her current + location, for example, using the DHCP civic mechanism defined in + [RFC4776]. A Location Object is constructed consisting of a single + PIDF document, with a single <tuple> or <device> element, a single + <status> element, a single <geopriv> element, and a single location + chunk residing in the <location-info> element. This document is + unambiguous, and should be interpreted consistently by receiving + nodes if sent over the network. + +3.2. Civic and Geospatial Location Information + + Mike is visiting his Seattle office and connects his laptop into the + Ethernet port in a spare cube. In this case, location information is + geodetic location, with the altitude represented as a building floor + number. Mike's main location is the point specified by the geodetic + coordinates. Further, Mike is on the second floor of the building + located at these coordinates. Applying rules #6 and #7, the + resulting compound location information is shown in Figure 2. + + + + + +Winterbottom, et al. Standards Track [Page 7] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:gml="http://www.opengis.net/gml" + xmlns:cl="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr" + entity="pres:mike@seattle.example.com"> + <dm:device id="mikepc"> + <gp:geopriv> + <gp:location-info> + <gml:Point srsName="urn:ogc:def:crs:EPSG::4326"> + <gml:pos>-43.5723 153.21760</gml:pos> + </gml:Point> + <cl:civicAddress> + <cl:FLR>2</cl:FLR> + </cl:civicAddress> + </gp:location-info> + <gp:usage-rules/> + <gp:method>Wiremap</gp:method> + </gp:geopriv> + <dm:deviceID>mac:8asd7d7d70cf</dm:deviceID> + <dm:timestamp>2007-06-22T20:57:29Z</dm:timestamp> + </dm:device> + </presence> + + Figure 2: PIDF-LO Containing a Compound Location + +3.3. Manual/Automatic Configuration of Location Information + + Loraine has a predefined civic location stored in her laptop, since + she normally lives in Sydney, the address is for her Sydney-based + apartment. Loraine decides to visit sunny San Francisco, and when + she gets there, she plugs in her laptop and makes a call. Loraine's + laptop receives a new location from the visited network in San + Francisco. As this system cannot be sure that the preexisting and + new location both describe the same place, Loraine's computer + generates a new PIDF-LO and will use this to represent Loraine's + location. If Loraine's computer were to add the new location to her + existing PIDF location document (breaking rule #3), then the correct + information may still be interpreted by the Location Recipient + providing Loraine's system applies rule #9. In this case, the + resulting order of location information in the PIDF document should + be San Francisco first, followed by Sydney. Since the information is + provided by different sources, rule #8 should also be applied and the + information placed in different tuples with the tuple containing the + San Francisco location first. + + + + + + +Winterbottom, et al. Standards Track [Page 8] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +3.4. Multiple Location Objects in a Single PIDF-LO + + Vanessa has her PC with her at the park, but due to a + misconfiguration, her PC reports her location as being in the office. + The resulting PIDF-LO will have a <device> element showing the + location of Vanessa's PC as the park, and a <person> element saying + that Vanessa is in her office. + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr" + xmlns:gml="http://www.opengis.net/gml" + xmlns:gs="http://www.opengis.net/pidflo/1.0" + entity="pres:ness@example.com"> + <dm:device id="nesspc-1"> + <gp:geopriv> + <gp:location-info> + <ca:civicAddress xml:lang="en-AU"> + <ca:country>AU</ca:country> + <ca:A1>NSW</ca:A1> + <ca:A3> Wollongong + </ca:A3><ca:A4>North Wollongong + </ca:A4> + <ca:RD>Flinders</ca:RD><ca:STS>Street</ca:STS> + <ca:RDBR>Campbell Street</ca:RDBR> + <ca:LMK> + Gilligan's Island + </ca:LMK> <ca:LOC>Corner</ca:LOC> + <ca:NAM> Video Rental Store </ca:NAM> + <ca:PC>2500</ca:PC> + <ca:ROOM> Westerns and Classics </ca:ROOM> + <ca:PLC>store</ca:PLC> + <ca:POBOX>Private Box 15</ca:POBOX> + </ca:civicAddress> + </gp:location-info> + <gp:usage-rules/> + <gp:method>GPS</gp:method> + </gp:geopriv> + <dm:deviceID>mac:1234567890ab</dm:deviceID> + <dm:timestamp>2007-06-22T20:57:29Z</dm:timestamp> + </dm:device> + <dm:person id="ness"> + <gp:geopriv> + <gp:location-info> + <gs:Circle srsName="urn:ogc:def:crs:EPSG::4326"> + <gml:pos>-34.410649 150.87651</gml:pos> + <gs:radius uom="urn:ogc:def:uom:EPSG::9001"> + + + +Winterbottom, et al. Standards Track [Page 9] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + 30 + </gs:radius> + </gs:Circle> + </gp:location-info> + <gp:usage-rules/> + <gp:method>Manual</gp:method> + </gp:geopriv> + <dm:timestamp>2007-06-24T12:28:04Z</dm:timestamp> + </dm:person> + </presence> + + Figure 3: PIDF-LO Containing Multiple Location Objects + +4. Geodetic Coordinate Representation + + The geodetic examples provided in RFC 4119 [RFC4119] are illustrated + using the <gml:location> element, which uses the <gml:coordinates> + element inside the <gml:Point> element, and this representation has + several drawbacks. Firstly, it has been deprecated in later versions + of GML (3.1 and beyond) making it inadvisable to use for new + applications. Secondly, the format of the coordinates type is opaque + and so can be difficult to parse and interpret to ensure consistent + results, as the same geodetic location can be expressed in a variety + of ways. The PIDF-LO Geodetic Shapes specification [GeoShape] + provides a specific GML profile for expressing commonly used shapes + using simple GML representations. The shapes defined in [GeoShape] + are the recommended shapes to ensure interoperability. + +5. Geodetic Shape Representation + + The cellular mobile world today makes extensive use of geodetic-based + location information for emergency and other location-based + applications. Generally, these locations are expressed as a point + (either in two or three dimensions) and an area or volume of + uncertainty around the point. In theory, the area or volume + represents a coverage in which the user has a relatively high + probability of being found, and the point is a convenient means of + defining the centroid for the area or volume. In practice, most + systems use the point as an absolute value and ignore the + uncertainty. It is difficult to determine if systems have been + implemented in this manner for simplicity, and even more difficult to + predict if uncertainty will play a more important role in the future. + An important decision is whether an uncertainty area should be + specified. + + + + + + + +Winterbottom, et al. Standards Track [Page 10] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + The PIDF-LO Geodetic Shapes specification [GeoShape] defines eight + shape types, most of which are easily translated into shape + definitions used in other applications and protocols, such as the + Open Mobile Alliance (OMA) Mobile Location Protocol (MLP). For + completeness, the shapes defined in [GeoShape] are listed below: + + o Point (2d and 3d) + + o Polygon (2d) + + o Circle (2d) + + o Ellipse (2d) + + o Arc band (2d) + + o Sphere (3d) + + o Ellipsoid (3d) + + o Prism (3d) + + The above-listed shapes MUST be implemented. + + The GeoShape specification [GeoShape] also describes a standard set + of coordinate reference systems (CRS), unit of measure (UoM) and + conventions relating to lines and distances. The use of the world + geodetic system 1984 (WGS84) [WGS84] coordinate reference system and + the usage of European petroleum survey group (EPSG) code 4326 (as + identified by the URN urn:ogc:def:crs:EPSG::4326, [CRS-URN]) for two- + dimensional (2d) shape representations and EPSG 4979 (as identified + by the URN urn:ogc:def:crs:EPSG::4979) for three-dimensional (3d) + volume representations is mandated. Distance and heights are + expressed in meters using EPSG 9001 (as identified by the URN + urn:ogc:def:uom:EPSG::9001). Angular measures MUST use either + degrees or radians. Measures in degrees MUST be identified by the + URN urn:ogc:def:uom:EPSG::9102, measures in radians MUST be + identified by the URN urn:ogc:def:uom:EPSG::9101. Angles + representing bearings are measured in a clockwise direction from + Northing, as defined by the WGS84 CRS, not magnetic north. + + Implementations MUST specify the CRS using the srsName attribute on + the outermost geometry element. The CRS MUST NOT be respecified or + changed for any sub-elements. The srsDimension attribute SHOULD be + omitted, since the number of dimensions in these CRSs is known. A + CRS MUST be specified using the above URN notation only; + implementations do not need to support user-defined CRSs. + + + + +Winterbottom, et al. Standards Track [Page 11] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + Numerical values for coordinates and measures are expressed using the + lexical representation for "double" defined in + [W3C.REC-xmlschema-2-20041028]. Leading zeros and trailing zeros + past the decimal point are not significant; for instance "03.07500" + is equivalent to "3.075". + + It is RECOMMENDED that uncertainty is expressed at a confidence of + 95% or higher. Specifying a convention for confidence enables better + use of uncertainty values. + +5.1. Polygon Restrictions + + The polygon shape type defined in [GeoShape] intentionally does not + place any constraints on the number of vertices that may be included + to define the bounds of a polygon. This allows arbitrarily complex + shapes to be defined and conveyed in a PIDF-LO. However, where + location information is to be used in real-time processing + applications, such as location-dependent routing, having arbitrarily + complex shapes consisting of tens or even hundreds of points could + result in significant performance impacts. To mitigate this risk, + Polygon shapes SHOULD be restricted to a maximum of 15 points (16 + including the repeated point) when the location information is + intended for use in real-time applications. This limit of 15 points + is chosen to allow moderately complex shape definitions while at the + same time enabling interoperation with other location transporting + protocols such as those defined in the 3rd Generation Partnership + Project (3GPP) (see [3GPP.23.032]) and OMA where the 15-point limit + is already imposed. + + The edges of a polygon are defined by the shortest path between two + points in space (not a geodesic curve). Two-dimensional points MAY + be interpreted as having a zero value for their altitude component. + To avoid significant errors arising from potential geodesic + interpolation, the length between adjacent vertices SHOULD be + restricted to a maximum of 130 km. More information relating to this + restriction is provided in [GeoShape]. + + A connecting line SHALL NOT cross another connecting line of the same + Polygon. + + Polygons MUST be defined with the upward normal pointing up. This is + accomplished by defining the vertices in a counter-clockwise + direction. + + Points specified in a polygon using three-dimensional coordinates + MUST all have the same altitude. + + + + + +Winterbottom, et al. Standards Track [Page 12] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +5.2. Shape Examples + + This section provides some examples of where some of the more complex + shapes are used, how they are determined, and how they are + represented in a PIDF-LO. Complete details on all of the GeoShape + types are provided in [GeoShape]. + +5.2.1. Point + + The point shape type is the simplest form of geodetic location + information (LI), which is natively supported by GML. The gml:Point + element is used when there is no known uncertainty. A point also + forms part of a number of other geometries. A point may be specified + using either WGS 84 (latitude, longitude) or WGS 84 (latitude, + longitude, altitude). Figure 4 shows a 2d point: + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:cl="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr" + xmlns:gml="http://www.opengis.net/gml" + entity="pres:point2d@example.com"> + <dm:device id="point2d"> + <gp:geopriv> + <gp:location-info> + <gml:Point srsName="urn:ogc:def:crs:EPSG::4326"> + <gml:pos>-34.407 150.883</gml:pos> + </gml:Point> + </gp:location-info> + <gp:usage-rules/> + <gp:method>Wiremap</gp:method> + </gp:geopriv> + <dm:deviceID>mac:1234567890ab</dm:deviceID> + <dm:timestamp>2007-06-22T20:57:29Z</dm:timestamp> + </dm:device> + </presence> + + Figure 4: PIDF-LO Containing a Two-Dimensional Point + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 13] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + Figure 5 shows a 3d point: + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:gml="http://www.opengis.net/gml" + entity="pres:point3d@example.com"> + <dm:device id="point3d"> + <gp:geopriv> + <gp:location-info> + <gml:Point srsName="urn:ogc:def:crs:EPSG::4979" + xmlns:gml="http://www.opengis.net/gml"> + <gml:pos>-34.407 150.883 24.8</gml:pos> + </gml:Point> + </gp:location-info> + <gp:usage-rules/> + <gp:method>Wiremap</gp:method> + </gp:geopriv> + <dm:deviceID>mac:1234567890ab</dm:deviceID> + <dm:timestamp>2007-06-22T20:57:29Z</dm:timestamp> + </dm:device> + </presence> + + Figure 5: PIDF-LO Containing a Three-Dimensional Point + +5.2.2. Polygon + + The polygon shape type may be used to represent a building outline or + coverage area. The first and last points of the polygon have to be + the same. For example, looking at the hexagon in Figure 6 with + vertices, A, B, C, D, E, and F. The resulting polygon will be + defined with 7 points, with the first and last points both having the + coordinates of point A. + + F--------------E + / \ + / \ + / \ + A D + \ / + \ / + \ / + B--------------C + + Figure 6: Example of a Polygon + + + + + + +Winterbottom, et al. Standards Track [Page 14] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:gml="http://www.opengis.net/gml" + entity="pres:hexagon@example.com"> + <tuple id="polygon-pos"> + <status> + <gp:geopriv> + <gp:location-info> + <gml:Polygon srsName="urn:ogc:def:crs:EPSG::4326"> + <gml:exterior> + <gml:LinearRing> + <gml:pos>43.311 -73.422</gml:pos> <!--A--> + <gml:pos>43.111 -73.322</gml:pos> <!--F--> + <gml:pos>43.111 -73.222</gml:pos> <!--E--> + <gml:pos>43.311 -73.122</gml:pos> <!--D--> + <gml:pos>43.411 -73.222</gml:pos> <!--C--> + <gml:pos>43.411 -73.322</gml:pos> <!--B--> + <gml:pos>43.311 -73.422</gml:pos> <!--A--> + </gml:LinearRing> + </gml:exterior> + </gml:Polygon> + </gp:location-info> + <gp:usage-rules/> + <gp:method>Wiremap</gp:method> + </gp:geopriv> + </status> + <timestamp>2007-06-22T20:57:29Z</timestamp> + </tuple> + </presence> + + Figure 7: PIDF-LO Containing a Polygon + + In addition to the form shown in Figure 7, GML supports a posList + that provides a more compact representation for the coordinates of + the Polygon vertices than the discrete pos elements. The more + compact form is shown in Figure 8. Both forms are permitted. + + + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 15] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:gml="http://www.opengis.net/gml" + entity="pres:hexagon@example.com"> + <tuple id="polygon-poslist"> + <status> + <gp:geopriv> + <gp:location-info> + <gml:Polygon srsName="urn:ogc:def:crs:EPSG::4326"> + <gml:exterior> + <gml:LinearRing> + <gml:posList> + 43.311 -73.422 43.111 -73.322 + 43.111 -73.222 43.311 -73.122 + 43.411 -73.222 43.411 -73.322 + 43.311 -73.422 + </gml:posList> + </gml:LinearRing> + </gml:exterior> + </gml:Polygon> + </gp:location-info> + <gp:usage-rules/> + <gp:method>Wiremap</gp:method> + </gp:geopriv> + </status> + <timestamp>2007-06-22T20:57:29Z</timestamp> + </tuple> + </presence> + + Figure 8: Compact Form of a Polygon Expressed in a PIDF-LO + + + + + + + + + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 16] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +5.2.3. Circle + + The circular area is used for coordinates in two-dimensional CRSs to + describe uncertainty about a point. The definition is based on the + one-dimensional geometry in GML, gml:CircleByCenterPoint. The center + point of a circular area is specified by using a two-dimensional CRS; + in three dimensions, the orientation of the circle cannot be + specified correctly using this representation. A point with + uncertainty that is specified in three dimensions should use the + sphere shape type. + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:gml="http://www.opengis.net/gml" + xmlns:gs="http://www.opengis.net/pidflo/1.0" + entity="pres:circle@example.com"> + <tuple id="circle"> + <status> + <gp:geopriv> + <gp:location-info> + <gs:Circle srsName="urn:ogc:def:crs:EPSG::4326"> + <gml:pos>42.5463 -73.2512</gml:pos> + <gs:radius uom="urn:ogc:def:uom:EPSG::9001"> + 850.24 + </gs:radius> + </gs:Circle> + </gp:location-info> + <gp:usage-rules/> + <gp:method>OTDOA</gp:method> + </gp:geopriv> + </status> + </tuple> + </presence> + + Figure 9: PIDF-LO Containing a Circle + +5.2.4. Ellipse + + An elliptical area describes an ellipse in two-dimensional space. + The ellipse is described by a center point, the length of its semi- + major and semi-minor axes, and the orientation of the semi-major + axis. Like the circular area (Circle), the ellipse MUST be specified + using the two-dimensional CRS. + + + + + + + + +Winterbottom, et al. Standards Track [Page 17] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:gml="http://www.opengis.net/gml" + xmlns:gs="http://www.opengis.net/pidflo/1.0" + entity="pres:Ellipse@somecell.example.com"> + <tuple id="ellipse"> + <status> + <gp:geopriv> + <gp:location-info> + <gs:Ellipse srsName="urn:ogc:def:crs:EPSG::4326"> + <gml:pos>42.5463 -73.2512</gml:pos> + <gs:semiMajorAxis uom="urn:ogc:def:uom:EPSG::9001"> + 1275 + </gs:semiMajorAxis> + <gs:semiMinorAxis uom="urn:ogc:def:uom:EPSG::9001"> + 670 + </gs:semiMinorAxis> + <gs:orientation uom="urn:ogc:def:uom:EPSG::9102"> + 43.2 + </gs:orientation> + </gs:Ellipse> + </gp:location-info> + <gp:usage-rules/> + <gp:method>Device-Assisted_A-GPS</gp:method> + </gp:geopriv> + </status> + <timestamp>2007-06-22T20:57:29Z</timestamp> + </tuple> + </presence> + + Figure 10: PIDF-LO Containing an Ellipse + + The gml:pos element indicates the position of the center, or origin, + of the ellipse. The gs:semiMajorAxis and gs:semiMinorAxis elements + are the length of the semi-major and semi-minor axes, respectively. + The gs:orientation element is the angle by which the semi-major axis + is rotated from the first axis of the CRS towards the second axis. + For WGS 84, the orientation indicates rotation from Northing to + Easting, which, if specified in degrees, is roughly equivalent to a + compass bearing (if magnetic north were the same as the WGS north + pole). Note: An ellipse with equal major and minor axis lengths is a + circle. + + + + + + + + + +Winterbottom, et al. Standards Track [Page 18] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +5.2.5. Arc Band + + The arc band shape type is commonly generated in wireless systems + where timing advance or code offsets sequences are used to compensate + for distances between handsets and the access point. The arc band is + represented as two radii emanating from a central point, and two + angles that represent the starting angle and the opening angle of the + arc. In a cellular environment, the central point is nominally the + location of the cell tower, the two radii are determined by the + extent of the timing advance, and the two angles are generally + provisioned information. + + For example, Paul is using a cellular wireless device and is 7 timing + advance symbols away from the cell tower. For a GSM-based network, + this would place Paul roughly between 3,594 meters and 4,148 meters + from the cell tower, providing the inner and outer radius values. If + the start angle is 20 degrees from north, and the opening angle is + 120 degrees, an arc band representing Paul's location would look + similar to Figure 11. + + N ^ ,.__ + | a(s) / `-. + | 20 / `-. + |--. / `. + | `/ \ + | /__ \ + | . `-. \ + | . `. \ + |. \ \ . + ---c-- a(o) -- | | --> + |. / 120 ' | E + | . / ' + | . / ; + .,' / + r(i)`. / + (3594m) `. / + `. ,' + `. ,' + r(o)`' + (4148m) + + Figure 11: Example of an Arc Band + + The resulting PIDF-LO is shown in Figure 12. + + + + + + + +Winterbottom, et al. Standards Track [Page 19] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:gml="http://www.opengis.net/gml" + xmlns:gs="http://www.opengis.net/pidflo/1.0" + entity="pres:paul@somecell.example.com"> + <tuple id="arcband"> + <status> + <gp:geopriv> + <gp:location-info> + <gs:ArcBand srsName="urn:ogc:def:crs:EPSG::4326"> + <gml:pos>-43.5723 153.21760</gml:pos> + <gs:innerRadius uom="urn:ogc:def:uom:EPSG::9001"> + 3594 + </gs:innerRadius> + <gs:outerRadius uom="urn:ogc:def:uom:EPSG::9001"> + 4148 + </gs:outerRadius> + <gs:startAngle uom="urn:ogc:def:uom:EPSG::9102"> + 20 + </gs:startAngle> + <gs:openingAngle uom="urn:ogc:def:uom:EPSG::9102"> + 20 + </gs:openingAngle> + </gs:ArcBand> + </gp:location-info> + <gp:usage-rules/> + <gp:method>TA-NMR</gp:method> + </gp:geopriv> + </status> + <timestamp>2007-06-22T20:57:29Z</timestamp> + </tuple> + </presence> + + Figure 12: PIDF-LO Containing an Arc Band + + An important note to make on the arc band is that the center point + used in the definition of the shape is not included in resulting + enclosed area, and that Target may be anywhere in the defined area of + the arc band. + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 20] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +5.2.6. Sphere + + The sphere is a volume that provides the same information as a circle + in three dimensions. The sphere has to be specified using a three- + dimensional CRS. Figure 13 shows the sphere shape type, which is + identical to the circle example, except for the addition of an + altitude in the provided coordinates. + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:gml="http://www.opengis.net/gml" + xmlns:gs="http://www.opengis.net/pidflo/1.0" + entity="pres:sphere@example.com"> + <tuple id="sphere"> + <status> + <gp:geopriv> + <gp:location-info> + <gs:Sphere srsName="urn:ogc:def:crs:EPSG::4979"> + <gml:pos>42.5463 -73.2512 26.3</gml:pos> + <gs:radius uom="urn:ogc:def:uom:EPSG::9001"> + 850.24 + </gs:radius> + </gs:Sphere> + </gp:location-info> + <gp:usage-rules/> + <gp:method>Device-Based_A-GPS</gp:method> + </gp:geopriv> + </status> + </tuple> + </presence> + + Figure 13: PIDF-LO Containing a Sphere + + + + + + + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 21] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +5.2.7. Ellipsoid + + The ellipsoid is the volume most commonly produced by GPS systems. + It is used extensively in navigation systems and wireless location + networks. The ellipsoid is constructed around a central point + specified in three dimensions, and three axes perpendicular to one + another are extended outwards from this point. These axes are + defined as the semi-major (M) axis, the semi-minor (m) axis, and the + vertical (v) axis, respectively. An angle is used to express the + orientation of the ellipsoid. The orientation angle is measured in + degrees from north, and represents the direction of the semi-major + axis from the center point. + + \ + _.-\""""^"""""-._ + .' \ | `. + / v m \ + | \ | | + | -c ----M---->| + | | + \ / + `._ _.' + `-...........-' + + Figure 14: Example of an Ellipsoid + + + + + + + + + + + + + + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 22] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + A PIDF-LO containing an ellipsoid appears as shown in Figure 15. + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:gml="http://www.opengis.net/gml" + xmlns:gs="http://www.opengis.net/pidflo/1.0" + entity="pres:somone@gpsreceiver.example.com"> + <tuple id="ellipsoid"> + <status> + <gp:geopriv> + <gp:location-info> + <gs:Ellipsoid srsName="urn:ogc:def:crs:EPSG::4979"> + <gml:pos>42.5463 -73.2512 26.3</gml:pos> + <gs:semiMajorAxis uom="urn:ogc:def:uom:EPSG::9001"> + 7.7156 + </gs:semiMajorAxis> + <gs:semiMinorAxis uom="urn:ogc:def:uom:EPSG::9001"> + 3.31 + </gs:semiMinorAxis> + <gs:verticalAxis uom="urn:ogc:def:uom:EPSG::9001"> + 28.7 + </gs:verticalAxis> + <gs:orientation uom="urn:ogc:def:uom:EPSG::9102"> + 90 + </gs:orientation> + </gs:Ellipsoid> + </gp:location-info> + <gp:usage-rules/> + <gp:method>Hybrid_A-GPS</gp:method> + </gp:geopriv> + </status> + <timestamp>2007-06-22T20:57:29Z</timestamp> + </tuple> + </presence> + + Figure 15: PIDF-LO Containing an Ellipsoid + + + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 23] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +5.2.8. Prism + + A prism may be used to represent a section of a building or range of + floors of building. The prism extrudes a polygon by providing a + height element. It consists of a base made up of coplanar points + defined in 3 dimensions all at the same altitude. The prism is then + an extrusion from this base to the value specified in the height + element. The height of the Prism MUST be a positive value. The + first and last points of the polygon have to be the same. + + For example, looking at the cube in Figure 16: if the prism is + extruded from the bottom up, then the polygon forming the base of the + prism is defined with the points A, B, C, D, A. The height of the + prism is the distance between point A and point E in meters. + + G-----F + /| /| + / | / | + H--+--E | + | C--|--B + | / | / + |/ |/ + D-----A + + Figure 16: Example of a Prism + + + + + + + + + + + + + + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 24] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + The resulting PIDF-LO is shown in Figure 17. + + <presence xmlns="urn:ietf:params:xml:ns:pidf" + xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10" + xmlns:gml="http://www.opengis.net/gml" + xmlns:gs="http://www.opengis.net/pidflo/1.0" + entity="pres:mike@someprism.example.com"> + <tuple id="prism"> + <status> + <gp:geopriv> + <gp:location-info> + <gs:Prism srsName="urn:ogc:def:crs:EPSG::4979"> + <gs:base> + <gml:Polygon> + <gml:exterior> + <gml:LinearRing> + <gml:posList> + 42.556844 -73.248157 36.6 <!--A--> + 42.656844 -73.248157 36.6 <!--B--> + 42.656844 -73.348157 36.6 <!--C--> + 42.556844 -73.348157 36.6 <!--D--> + 42.556844 -73.248157 36.6 <!--A--> + </gml:posList> + </gml:LinearRing> + </gml:exterior> + </gml:Polygon> + </gs:base> + <gs:height uom="urn:ogc:def:uom:EPSG::9001"> + 2.4 + </gs:height> + </gs:Prism> + </gp:location-info> + <gp:usage-rules/> + <gp:method>Wiremap</gp:method> + </gp:geopriv> + </status> + <timestamp>2007-06-22T20:57:29Z</timestamp> + </tuple> + </presence> + + Figure 17: PIDF-LO Containing a Prism + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 25] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +6. Security Considerations + + The primary security considerations relate to how location + information is conveyed and used, which are outside the scope of this + document. This document is intended to serve only as a set of + guidelines as to which elements MUST or SHOULD be implemented by + systems wishing to perform location dependent routing. The + ramification of such recommendations is that they extend to devices + and clients that wish to make use of such services. + +7. Acknowledgments + + The authors would like to thank the GEOPRIV working group for their + discussions in the context of PIDF-LO, in particular Carl Reed, Ron + Lake, James Polk, Henning Schulzrinne, Jerome Grenier, Roger Marshall + and Robert Sparks. Furthermore, we would like to thank Jon Peterson + as the author of PIDF-LO and Nadine Abbott for her constructive + comments in clarifying some aspects of the document. + + Thanks to Karen Navas for pointing out some omissions in the + examples. + +8. References + +8.1. Normative References + + [GeoShape] Thomson, M. and C. Reed, "GML 3.1.1 PIDF-LO Shape + Application Schema for use by the Internet Engineering + Task Force (IETF)", Candidate OpenGIS Implementation + Specification 06-142r1, Version: 1.0, April 2007. + + [OGC-GML3.1.1] + Portele, C., Cox, S., Daisy, P., Lake, R., and A. + Whiteside, "Geography Markup Language (GML) 3.1.1", + OGC 03-105r1, July 2003. + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object + Format", RFC 4119, December 2005. + + [RFC4479] Rosenberg, J., "A Data Model for Presence", RFC 4479, + July 2006. + + [RFC5139] Thomson, M. and J. Winterbottom, "Revised Civic Location + Format for Presence Information Data Format Location + Object (PIDF-LO)", RFC 5139, February 2008. + + + +Winterbottom, et al. Standards Track [Page 26] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + + [W3C.REC-xmlschema-2-20041028] + Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes + Second Edition", World Wide Web Consortium + Recommendation REC-xmlschema-2-20041028, October 2004, + <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>. + +8.2. Informative References + + [3GPP.23.032] + 3rd Generation Partnership Project, "Universal + Geographical Area Description (GAD)", 3GPP TS 23.032 + V6.0.0, January 2005, + <http://www.3gpp.org/ftp/Specs/html-info/23032.htm>. + + [CRS-URN] Whiteside, A., "GML 3.1.1 Common CRSs Profile", OGC 03- + 105r1, November 2005. + + [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and + J. Polk, "Geopriv Requirements", RFC 3693, February 2004. + + [RFC4776] Schulzrinne, H., "Dynamic Host Configuration Protocol + (DHCPv4 and DHCPv6) Option for Civic Addresses + Configuration Information", RFC 4776, November 2006. + + [WGS84] US National Imagery and Mapping Agency, "Department of + Defense (DoD) World Geodetic System 1984 (WGS 84), Third + Edition", NIMA TR8350.2, January 2000. + + + + + + + + + + + + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 27] + +RFC 5491 GEOPRIV PIDF-LO Usage March 2009 + + +Authors' Addresses + + James Winterbottom + Andrew Corporation + Wollongong + NSW Australia + + EMail: james.winterbottom@andrew.com + + + Martin Thomson + Andrew Corporation + Wollongong + NSW Australia + + EMail: martin.thomson@andrew.com + + + Hannes Tschofenig + Nokia Siemens Networks + Linnoitustie 6 + Espoo 02600 + Finland + + Phone: +358 (50) 4871445 + EMail: Hannes.Tschofenig@gmx.net + URI: http://www.tschofenig.priv.at + + + + + + + + + + + + + + + + + + + + + + + + +Winterbottom, et al. Standards Track [Page 28] + |