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Versions: (draft-mayrhofer-geopriv-geo-uri) 00 01 02 03 04 05 06 07 RFC 5870

GEOPRIV -- Geographic                                       A. Mayrhofer
Location/Privacy Working Group                                    nic.at
Internet-Draft                                               C. Spanring
Expires: March 5, 2010                                September 01, 2009


   A Uniform Resource Identifier for Geographic Locations ('geo' URI)
                     draft-ietf-geopriv-geo-uri-02

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   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.

Abstract

   This document specifies an Uniform Resource Identifier (URI) for
   geographic locations using the 'geo' scheme name.  A 'geo' URI
   identifies a physical location in a two- or three-dimensional
   coordinate reference system in a compact, simple, human-readable, and
   protocol independent way.  The default coordinate reference system
   used is WGS-84.






































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5

   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6

   3.  IANA Registration of 'geo' URI Scheme  . . . . . . . . . . . .  6
     3.1.  URI Scheme Name  . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  Status . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.3.  URI Scheme Syntax  . . . . . . . . . . . . . . . . . . . .  7
     3.4.  URI Scheme Semantics . . . . . . . . . . . . . . . . . . .  8
       3.4.1.  Coordinate Reference System Identification . . . . . .  8
       3.4.2.  Component Description for WGS-84 . . . . . . . . . . .  8
       3.4.3.  Location Uncertainty . . . . . . . . . . . . . . . . .  9
       3.4.4.  URI Comparison . . . . . . . . . . . . . . . . . . . .  9
       3.4.5.  Interpretation of Undefined Altitude . . . . . . . . . 10
     3.5.  Encoding Considerations  . . . . . . . . . . . . . . . . . 10
     3.6.  Applications/Protocols that use this URI Scheme  . . . . . 10
     3.7.  Interopability Considerations  . . . . . . . . . . . . . . 11
     3.8.  Contact  . . . . . . . . . . . . . . . . . . . . . . . . . 11
     3.9.  Author/Change controller . . . . . . . . . . . . . . . . . 11
     3.10. References . . . . . . . . . . . . . . . . . . . . . . . . 11

   4.  'geo' URI Parameters Registry  . . . . . . . . . . . . . . . . 11

   5.  URI Operations . . . . . . . . . . . . . . . . . . . . . . . . 12

   6.  Use Cases and Examples . . . . . . . . . . . . . . . . . . . . 13
     6.1.  Plain 'geo' URI Example  . . . . . . . . . . . . . . . . . 13
     6.2.  Hyperlink  . . . . . . . . . . . . . . . . . . . . . . . . 13
     6.3.  'geo' URI in 2-dimensional barcode . . . . . . . . . . . . 14

   7.  GML Mappings . . . . . . . . . . . . . . . . . . . . . . . . . 14
     7.1.  2D GML 'Point' . . . . . . . . . . . . . . . . . . . . . . 15
     7.2.  3D GML 'Point' . . . . . . . . . . . . . . . . . . . . . . 15
     7.3.  GML 'Circle' . . . . . . . . . . . . . . . . . . . . . . . 15
     7.4.  GML 'Sphere' . . . . . . . . . . . . . . . . . . . . . . . 16

   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
     8.1.  'geo' URI Scheme . . . . . . . . . . . . . . . . . . . . . 16
     8.2.  URI Parameter Registry . . . . . . . . . . . . . . . . . . 17
       8.2.1.  Registry Contents  . . . . . . . . . . . . . . . . . . 17
       8.2.2.  Registration Policy  . . . . . . . . . . . . . . . . . 17

   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
     9.1.  Invalid Locations  . . . . . . . . . . . . . . . . . . . . 18
     9.2.  Location Privacy . . . . . . . . . . . . . . . . . . . . . 18




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   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18

   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 19
     11.2. Informative References . . . . . . . . . . . . . . . . . . 19

   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . . 19

   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20










































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1.  Introduction

   An increasing number of Internet protocols and data formats are
   extended by specifications for adding spatial (geographic) location.
   In most cases, latitude as well as longitude of simple points are
   added as new attributes to existing data structures.  However, all
   those methods are very specific to a certain data format or protocol,
   and don't provide a protocol independent, compact and generic way to
   refer to a physical geographic location.

   Over the past few years, fast emerging location aware applications
   and location based services were observable on the Internet.  Most
   web search engines use geographic information, and a vivid open
   source mapping community brought an enormous momentum into location
   aware technology.  A wide range of tools and data sets which formerly
   were accessible to professional only became available for a wider
   audience.

   The 'geo' URI scheme is another step into that direction and aims to
   facilitate, support and standardize the problem of location
   identification in geospatial services and applications.  Accessing
   information about a particular location on earth or trigger further
   services shouldn't be any harder than clicking on a 'mailto:' link
   and write an email straight away.

   According to [RFC3986], a Uniform Resource Identifier (URI) is "a
   compact sequence of characters that identifies an abstract or
   physical resource".  The 'geo' URI scheme defined in this document
   identifies geographic locations (a physical resource) in a coordinate
   references system (CRS), per default in World Geodetic System 1984
   (WGS-84) [WGS84].  The scheme provides the textual representation of
   the location's spatial coordinates in either two or three dimensions
   (latitude, longitude, and optionally altitude for the default CRS of
   WGS-84).

   Such URIs are independent from a specific protocol, application, or
   data format, and can be used in any other protocol or data format
   that supports inclusion of arbitrary URIs.

   For the sake of usability, the definition of the URI scheme is
   strictly focused on the simplest, but also most common representation
   of a spatial location - a single point in a well known CRS.  The
   provision of more complex geometries or locations described by civic
   addresses is out of scope of this document.

   The optional "crs" URI parameter described below may be used by
   future specifications to define the use of CRSes other than WGS-84.
   This is primarily intended to cope with the case of another CRS



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   replacing WGS-84 as the predominantly used one, rather than allowing
   the arbitrary use of thousands of CRSes for the URI (which would
   clearly affect interopability).  The definition of "crs" values
   beyond the default of "wgs84" is therefore out of scope of this
   document.

   Note: The choice of WGS-84 as the default CRS is based on the
   widespread availability of Global Positioning System (GPS) devices,
   which use the WGS-84 reference system.  It is anticipated that such
   devices serve as one of the primary data sources for authoring 'geo'
   URIs, hence the adoption of the native GPS reference system for the
   URI scheme.  Also, many other data formats for representing
   geographic locations use the WGS-84 reference system, which makes
   transposing from and to such data formats less error prone (no re-
   projection involved).  It is also believed that the burden of
   potentially required spatial transformations should be put on the
   author rather then the consumer of 'geo' URI instances.


2.  Terminology

   Geographic locations in this document are defined using WGS 84 (World
   Geodetic System 1984), equivalent to the International Association of
   Oil & Gas Producers (OGP) Surveying and Positioning Committee EPSG
   (European Petroleum Survey Group) code 4326 (2 dimensions) and 4979
   (3 dimensions).  This document does not assign responsibilities for
   coordinate transformations from and to other Spatial Reference
   Systems.

   A 2-dimensional WGS-84 coordinate value is here represented as a
   comma-delimited latitude/longitude pair, measured in decimal degrees
   (un-projected).  A 3-dimensional WGS-84 coordinate value is here
   represented by appending a comma-delimited altitude value in meters
   to such pairs.

   Latitudes range from -90 to 90 and longitudes range from -180 to 180.
   Coordinates in the Southern and Western hemispheres as well as
   altitudes below the WGS-84 reference geoid are signed negative with a
   leading dash.

   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 [RFC2119].


3.  IANA Registration of 'geo' URI Scheme

   This section contains the fields required for the URI scheme



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   registration, following the guidelines in section 5.4 of [RFC4395].

3.1.  URI Scheme Name

   geo

3.2.  Status

   permanent

3.3.  URI Scheme Syntax

   The syntax of the 'geo' URI scheme is specified below in Augmented
   Backus-Naur Form (ABNF) [RFC5234]:

             geo-URI       = geo-scheme ":" geo-path
             geo-scheme    = "geo"
             geo-path      = coordinates *p
             coordinates   = coord-a "," coord-b [ "," coord-c ]

             coord-a       = num
             coord-b       = num
             coord-c       = num

             p             = crsp / uncp / parameter
             crsp          = ";crs=" crslabel
             crslabel      = "wgs84" / labeltext
             uncp          = ";u=" pnum
             parameter     = ";" pname [ "=" pvalue ]
             pname         = labeltext
             pvalue        = 1*paramchar
             paramchar     = p-unreserved / unreserved / pct-encoded

             labeltext     = 1*( alphanum / "-" )
             pnum          = 1*DIGIT [ "." 1*DIGIT ]
             num           = [ "-" ] pnum
             unreserved    = alphanum / mark
             mark          = "-" / "_" / "." / "!" / "~" / "*" /
                             "'" / "(" / ")"
             pct-encoded   = "%" HEXDIG HEXDIG
             p-unreserved  = "[" / "]" / "/" / ":" / "&" / "+" / "$"
             alphanum      = ALPHA / DIGIT

   Both "crs" and "u" parameters MUST NOT appear more than once each.
   The "crs" and "u" parameters MUST be given before any other
   parameters that may be defined in future extensions.  The "crs"
   parameter MUST be given first if both "crs" and "u" are used.  The
   definition of other parameters, and "crs" values beyond the default



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   value of "wgs84" is out of scope of this document.  Section 8.2
   discusses the IANA registration of such additional parameters and
   values.

   In case the URI identifies a location in the default CRS of WGS-84,
   its sub-components are further restricted as follows:

             coord-a        = latitude
             coord-b        = longitude
             coord-c        = altitude

             latitude       = [ "-" ] 1*2DIGIT [ "." 1*DIGIT ]
             longitude      = [ "-" ] 1*3DIGIT [ "." 1*DIGIT ]
             altitude       = [ "-" ] 1*DIGIT [ "." 1*DIGIT ]

3.4.  URI Scheme Semantics

   Data contained in a 'geo' URI identifies a physical resource: A
   spatial location on earth identified by the geographic coordinates
   encoded in the URI.

3.4.1.  Coordinate Reference System Identification

   The semantics of the 'coordinates' component depends on the CRS of
   the URI.  The CRS itself is identified by the optional 'crs'
   parameter.  A URI instance uses the default WGS-84 CRS if the 'crs'
   parameter is either missing, or contains the value of 'wgs84'.  Other
   'crs' values are currently not defined, but may be specified by
   future documents.

   Interpretation of coordinates in a wrong CRS produces invalid
   location information.  Consumers of 'geo' URIs therefore MUST NOT
   ignore the 'crs' parameter if given, and MUST NOT interpret the
   'coordinates' component without considering and understanding the
   'crs' parameter value.

   The following component description refers to the use of the default
   CRS (WGS-84) only.  Future documents specifying other 'crs' parameter
   values MUST provide similar descriptions for the 'coordinates' sub-
   components in the described CRS.

3.4.2.  Component Description for WGS-84

   The "latitude", "longitude" and "altitude" components as specified in
   the URI scheme syntax ( Section 3.3) are to be used as follows:






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   o  The "latitude" component MUST contain the latitude of the
      identified location in decimal degrees in the reference system
      WGS-84.
   o  The "longitude" component MUST contain the longitude of the
      identified location in decimal degrees in the reference system
      WGS-84.
   o  If present, the OPTIONAL "altitude" component MUST contain the
      identified altitude in meters in the reference system WGS-84.

   If the altitude of the location is unknown, the "altitude" component
   MUST NOT be present in the URI.  Specifically, unknown altitude MUST
   NOT be represented by setting the 'altitude' component to "0" (or any
   other arbitrary value).

   The "longitude" components of coordinate values reflecting the poles
   (latitude set to -90 or 90 degrees) SHOULD be set to "0", although
   consumers of "geo" URIs MUST accept such URIs with any longitude
   value from -180 to 180.

   'geo' URIs with longitude values outside the range of -180 to 180
   decimal degrees or with latitude values outside the range of -90 to
   90 degrees MUST be considered invalid.

3.4.3.  Location Uncertainty

   The 'u' ("uncertainty") parameter indicates the amount of uncertainty
   in the location as a value in meters.  Where a geo URI is used to
   identify the location of a particular subject, uncertainty indicates
   the uncertainty with which the identified location of the subject is
   known.

   The 'u' parameter is optional and it can appear only once.  If
   uncertainty is not specified, this indicates that uncertainty is
   unknown or unspecified.  If the intent is to indicate a specific
   point in space, uncertainty MAY be set to zero.  Zero uncertainty and
   absent uncertainty are never the same thing.

   Note: The number of significant digits of the value in the
   'coordinates' component MUST NOT be interpreted as an indication to
   uncertainty.

3.4.4.  URI Comparison

   Two 'geo' URIs are equal when they use the same CRS, and their
   'coord-a', 'coord-b', 'coord-c' and 'u' values are mathematically
   identical.

   Two URIs use the same CRS if both have the 'crs' parameter omitted,



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   or both have the same 'crs' parameter value, or one has the 'crs'
   parameter omitted while the other URI specifies the default CRS
   explicitely with a 'crs' parameter value of "wgs84".

   For the default CRS of WGS-84, the following definitions apply in
   addition:
   o  Where the 'latitude' component of a 'geo' URI is set to either 90
      or -90 degrees, the 'longitude' component MUST be ignored in
      comparison operations ("poles case").
   o  A 'longitude' component of 180 degrees MUST be considered equal a
      'longitude' component of -180 degrees for the purpose of URI
      comparison ("date line" case).

   An URI with undefined (missing) 'coord-c' (altitude) value MUST NOT
   be considered equal to an URI containing an 'coord-c' value, even if
   the remaining values 'coord-a', 'coord-b' and 'u' are equivalent.

3.4.5.  Interpretation of Undefined Altitude

   A consumer of a 'geo' URI in the WGS-84 CRS with undefined 'altitude'
   MAY assume that the URI refers to the respective location on earth's
   physical surface at the given 'latitude' and 'longitude' coordinate.

   However, as defined above, altitudes are relative to the WGS-84
   reference geoid rather than earth's surface.  Hence, an altitude
   value of 0 MUST NOT be mistaken to refer to "ground elevation".

3.5.  Encoding Considerations

   The 'coordinates' path component of the 'geo' URI (see Section 3.3)
   uses a comma (",") as a delimiter for subcomponents.  This delimiter
   MUST NOT be percent encoded.

   It is RECOMMENDED that for readability the contents of 'coord-a',
   'coord-b' and 'coord-c' subcomponents, as well as the 'crs' and 'u'
   parameters are never percent encoded.

   Regarding internationalization, the currently specified components do
   allow for ASCII characters exclusively, and therefore don't require
   internationalization- Future specifications of additional parameters
   might allow for introduction of non-ASCII values.  Such
   specifications MUST describe internationalization considerations for
   those parameters and their values.

3.6.  Applications/Protocols that use this URI Scheme

   As many other URI scheme definitions, the 'geo' URI provides resource
   identification independent of a specific application or protocol.



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   Examples of potential protocol mappings and use cases can be found in
   Section 6.

3.7.  Interopability Considerations

   Like other new URI schemes, the 'geo' URI requires support in client
   applications.  Users of applications which are not aware of the 'geo'
   scheme are likely unable to make direct use of the information in the
   URI.  However, the simple structure of the 'geo' URI would even allow
   manual dereference by humans.

   Clients MUST NOT attempt to dereference URIs given in an CRS that is
   unknown to the client, because doing so would produce entirely bogus
   results.

   Authors of 'geo' URIs should carefully check that coordinate
   components are set in the right CRS and in the specified order, since
   wrong order of those components (or use of coordinates in a different
   CRS without transformation) are commonly observed mistakes producing
   completely bogus locations.

   The number of digits in the coordinates values MUST NOT be
   interpreted as an indication to a certain level of accuracy or
   uncertainty.

3.8.  Contact

      Alexander Mayrhofer <alexander.mayrhofer@nic.at>
      Christian Spanring <cspanring@gmail.com>

3.9.  Author/Change controller

   The 'geo' URI scheme is registered under the IETF part of the URI
   tree.  As such, change control is up to the IETF.

3.10.  References

   RFC XXXX [change to RFC number once assigned]


4.  'geo' URI Parameters Registry

   This specification creates a new IANA Registry named "'geo' URI
   Parameters Registry".  Parameters for the 'geo' URI and values for
   these parameters MUST be registered with IANA to prevent namespace
   collisions, and provide interopability.

   Some parameters accept values that are constrained by a syntax



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   definition only, while others accept values from a predefined set
   only.  Some parameters might not accept any values at all ("flag"
   type parameter).

   The registration of values is REQUIRED for parameters that accept
   values from a predefined set only.

   The specification of a parameter MUST fully explain the syntax,
   intended usage and semantics of the parameter.  This ensures
   interopability between independent implementations.

   For parameters that are neither restricted to a set of predefined
   values nor of the "flag" type described above, the syntax of allowed
   values MUST be described in the specification, for example by using
   ABNF.

   Documents defining new parameters (or new values for existing
   parameters) MUST register them with IANA, as explained in
   Section 8.2.

   The 'geo' URI Parameter Registry contains a column named "Value
   Restriction" that describes whether or not a parameter accepts a
   value, and whether values are restricted to a predefined set.  That
   column accepts the following values:

   o  "No value": The parameter does not accept any values, and is to be
      used as a "flag" only.
   o  "Predefined": The parameter does accept values from a predefined
      set only, as specified in a RFC or other permanent and readily
      available public specification.
   o  "Constrained": The parameter accepts arbitrary values that are
      only constrained by a syntax as specified in a RFC or other
      permanent and readily available public specification.


5.  URI Operations

   Currently, just one operation on a 'geo' URI is defined - location
   dereference: In that operation, a client dereferences the URI by
   extracting the geographical coordinates from the URI path component
   ('geo-path' in the ABNF).  Further use of those coordinates (and the
   uncertainty value from the 'u' parameter) is then up to the
   application processing the URI, and might depend on the context of
   the URI.

   An application may then use this location information for various
   purposes, for example:




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   o  A web browser could use that information to open a web mapping
      service of the user's choice, and display a map of the location

   o  A navigational device such as a Global Positioning System (GPS)
      receiver could offer the user to start navigation to the location.

   Note that the examples and use cases aboves as well as in the next
   section are non-normative, and provided for information only.


6.  Use Cases and Examples

6.1.  Plain 'geo' URI Example

   The following 3-dimensional 'geo' URI example references to the
   office location of one of the authors in Vienna, Austria:

   geo:48.2010,16.3695,183

   A user could type the data extracted from this URI into a electronic
   navigation device, or even use it to locate the identified location
   on a paper map.

6.2.  Hyperlink

   'geo' URIs (like any other URI scheme) could also be embedded as
   hyperlinks in web pages.  A Hyper Text Markup Language (HTML) snippet
   with such a hyperlink could look like:

      <p>one of Vienna's popular sights is the
      <a href='geo:48.198634,16.371648;crs=wgs84'>Karlskirche</a>.

   A web browser could extract the coordinates from the HTML snippet,
   and offer the user various options (based on configuration, context),
   for example:

   o  Display a small map thumbnail when the mouse pointer hovers over
      the link.

   o  Switch to a mapping service of the user's choice once the link is
      selected.

   o  Locate nearby resources, for example by comparing the 'geo' URI
      with locations extracted from GeoRSS feeds the user has subscribed
      to.






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   o  Convert the coordinates to a format suitable for uploading to a
      navigation device.

   Note that the URI in this example also makes use of the explicit
   specification of the CRS by using the 'crs' parameter.

6.3.  'geo' URI in 2-dimensional barcode

   Due to it's short length, a 'geo' URI could easily be encoded in
   2-dimensional barcodes.  Such barcodes could be printed on business
   cards, flyers, paper maps and subsequently used by mobile devices,
   for example as follows:

   1.  User identifies such a barcode on a flyer and uses the camera on
       his mobile phone to photograph and decode the barcode

   2.  The mobile phone dereferences the 'geo' URI, and offers the user
       to calculate a navigation route to the identified location.

   3.  Using the builtin GPS receiver, the user follows the navgiation
       instructions to reach the location


7.  GML Mappings

   The Geographic Markup Language (GML) by the Open Geospatial
   Consortium (OGC) is a set of XML schemas to represent geographical
   features.  Since GML is widely accepted, this document includes
   instructions on how to transpose 'geo' URIs from and to GML
   documents.  The instructions in this section are not normative.

   For the following sections, "%lat%", "%lon%", "%alt%" and "%unc%" are
   placeholders for latitude, longitude, altitude and uncertainty
   values.  The mappings use WGS-84, and are defined in the following
   sections.

   Note: GML documents in other reference systems could be used as well
   if a transformation into "urn:ogc:def:crs:EPSG::4979" or
   "urn:ogc:def:crs:EPSG::4326" is defined and applied before the
   mapping step.  Such transformations are typically not lossless.

   GML uses the 'double' type from XML schema, and the mapping examples
   assume that numbers in the form of "3.32435e2" in GML are properly
   converted to decimal when placed in the 'geo' URI.







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7.1.  2D GML 'Point'

   A 2D GML 'Point' [RFC5491] is constructed from a 'geo' URI that has
   two coordinates and an uncertainty ("u") parameter that is absent or
   zero.  A GML point is always converted to a 'geo' URI that has no
   uncertainty parameter.

   'geo' URI:

      geo:%lat%,%lon%

   GML document:

     <Point srsName="urn:ogc:def:crs:EPSG::4326"
            xmlns="http://www.opengis.net/gml">
       <pos>%lat% %lon%</pos>
     </Point>

   Note that a 'geo' URI with an uncertainty value of zero is converted
   to a GML 'Point', but a GML 'Point' cannot be translated to a 'geo'
   URI with zero uncertainty.

7.2.  3D GML 'Point'

   A 3D GML 'Point' [RFC5491] is constructed from a 'geo' URI that has
   three coordinates and an uncertainty parameter that is absent or
   zero.  A GML point is always converted to a 'geo' URI that has no
   uncertainty parameter.

   'geo' URI:

      geo:%lat%,%lon%,%alt%

   GML document:

     <Point srsName="urn:ogc:def:crs:EPSG::4979"
            xmlns="http://www.opengis.net/gml">
       <pos>%lat% %lon% %alt%</pos>
     </Point>

7.3.  GML 'Circle'

   A GML 'Circle' [RFC5491] is constructed from a 'geo' URI that has two
   coordinates and an uncertainty parameter that is present and non-
   zero.






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   'geo' URI:

      geo:%lat%,%lon%;u=%unc%

   GML document:

      <gs:Circle srsName="urn:ogc:def:crs:EPSG::4326"
                 xmlns:gml="http://www.opengis.net/gml"
                 xmlns:gs="http://www.opengis.net/pidflo/1.0">
        <gml:pos>%lat% %lon%</gml:pos>
        <gs:radius uom="urn:ogc:def:uom:EPSG::9001">
          %unc%
        </gs:radius>
      </gs:Circle>

7.4.  GML 'Sphere'

   A GML 'sphere' [RFC5491] is constructed from a 'geo' URI that has
   three coordinates and an uncertainty parameter that is present and
   non-zero.

   'geo' URI:

      geo:%lat%,%lon%,%alt%;u=%unc%

   GML document:

      <gs:Sphere srsName="urn:ogc:def:crs:EPSG::4979"
                 xmlns:gml="http://www.opengis.net/gml"
                 xmlns:gs="http://www.opengis.net/pidflo/1.0">
        <gml:pos>%lat% %lon% %alt%</gml:pos>
        <gs:radius uom="urn:ogc:def:uom:EPSG::9001">
          %unc%
        </gs:radius>
      </gs:Sphere>


8.  IANA Considerations

8.1.  'geo' URI Scheme

   This document requests assignment of the 'geo' URI scheme in the IETF
   part of the URI scheme tree, according to the guidelines in BCP 115
   (RFC 4395) [RFC4395].  The definitions required for the assignment
   are contained in Section 3.






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8.2.  URI Parameter Registry

   This document creates a new IANA Registry named "geo URI Parameters",
   according to the information in Section 4 and the definition in this
   section.

8.2.1.  Registry Contents

   When registering a new 'geo' URI Parameter, the following information
   MUST be provided:

   o  Name of the Parameter.
   o  Whether the Parameter accepts no value ("No value"), values from a
      predefined set ("Predefined"), or values constrained by a syntax
      only ("Constrained").
   o  Reference to the RFC or other permanent and readily available
      public specification defining the parameters and the new values.

   When registering a new value for an existing 'geo' URI Parameter, the
   following information MUST be provided:

   o  Name of the Parameter.
   o  Reference to the RFC or other permanent and readily available
      public specification defining the new values.

   The following table provides the initial values for this registry:

       Parameter Name          Value Restriction     Reference(s)
       ----------------------------------------------------------
       crs                     Predefined            [RFCxxxx]
       u                       Constrained           [RFCxxxx]

   [Note to RFC Editor: Replace RFCxxxx with reference to this document]

8.2.2.  Registration Policy

   The Registration Policy for 'geo' URI Parameters and their value
   definitions shall be "Specification Required, Designated Expert", as
   defined in [RFC5226].


9.  Security Considerations

   Because the 'geo' URI is not tied to any specific protocol, and
   identifies a physical location rather than a network resource, most
   of the general security considerations on URIs (Section 7 of RFC
   3986) do not apply.  However, the following (additional) issues
   apply:



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9.1.  Invalid Locations

   The URI syntax (Section 3.3) makes it possible to construct 'geo'
   URIs which don't identify a valid location on earth.  Applications
   MUST NOT use URIs with such values, and SHOULD warn the user when
   such URIs are encountered.

   An example of such an URI refering to an invalid location would be
   <geo:94,0> (latitude "beyond" north pole).

9.2.  Location Privacy

   A 'geo' URI by itself is just an opaque reference to a physical
   location, expressed by a set of spatial oordinates.  This does not
   fit the "Location Information" definition according to Section 5.2 of
   GEOPRIV Requirements [RFC3693], because there is not necessarily a
   "Device" involved.

   Because there is also no way to specify the identity of a "Target" in
   a 'geo' URI by itself, it does also not fit the specification of an
   "Location Object" (Section 5.2 of RFC3693).

   However, by putting a 'geo' URI into a context that allows
   identification of a "Target", the URI might become part of a
   "Location Object", and would then be subject to GEOPRIV rules.

   Therefore, Publishers of 'geo' URIs that are put into such contexts
   MUST consider privacy issues, particularly in cases where a URI
   instance is combined with Personally Identifyable Information (PII)
   with the intent to describe the location of a Target that is a
   person.


10.  Acknowledgements

   Martin Thomson has provided significant text around the definition of
   the "uncertainty" parameter and the GML mappings.

   The authors further wish to acknowledge the helpful contributions
   from Carl Reed, Bill McQuillan, Martin Kofal, Andrew Turner, Kim
   Sanders, Ted Hardie, Culllen Jennings, Klaus Darilion and Bjorn
   Hoehrmann.


11.  References






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11.1.  Normative References

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [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.

11.2.  Informative References

   [RFC4395]  Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
              Registration Procedures for New URI Schemes", BCP 115,
              RFC 4395, February 2006.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC3693]  Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
              J. Polk, "Geopriv Requirements", RFC 3693, February 2004.

   [WGS84]    National Imagery and Mapping Agency, "Department of
              Defense World Geodetic System 1984, Third Edition",
              NIMA TR8350.2, January 2000.


Appendix A.  Change Log

   [Note to editors: This section is to be removed before publication -
   XML source available on request]

   draft-ietf-geopriv-geo-uri-02
   o  Added IANA registry for 'geo' URI Parameters and values
   o  Moved change log to appendix
   o  Added "u" parameter to ABNF, restructred ABNF slightly
   o  Added new section describing uncertainty
   o  Changed mapping examples, added some for uncertainty





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   o  Added text that number of digits shouldn't be confused with
      uncertainty or accuracy
   o  marked GML mappings as non-normative based on URI expert review
      advice
   o  added internationalization consideration section
   o  various other changes based on Expert Review

   draft-ietf-geopriv-geo-uri-01
   o  added parameters to ABNF
   o  added optional 'crs' parameter to allow future use of other CRSes
   o  Many other changes to not preclude the future specification of
      other CRSes.
   o  some typos fixes - credits Bill McQuillan

   draft-ietf-geopriv-geo-uri-00
   o  submitted as WG item
   o  changed IPR text because of text used from RFC 4395
   o  added considerations for comparing +180/-180 longitude URIs
   o  some editorial changes

   draft-mayrhofer-geopriv-geo-uri-01
   o  added terminology text about WGS-84 (credits Carl Reed)
   o  removed "resolution" / "uncertainty" text
   o  added considerations regarding poles
   o  added text about invalid URIs

   draft-mayrhofer-geopriv-geo-uri-00
   o  Initial version under new name, reverting to "plain" lat/lon
      scheme, with the "tiling" scheme moved to seperate draft
      (potentially published as "draft-mayrhofer-geopriv-geotile-uri").
      refer to draft-mayrhofer-geo-uri-01 for the history of this
      document.
   o  Added GML mapping section

   draft-mayrhofer-geo-uri-01
   o  removed parameters

   draft-mayrhofer-geo-uri-00
   o  initial draft












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Authors' Addresses

   Alexander Mayrhofer
   nic.at GmbH
   Karlsplatz 1/2/9
   Wien  A-1010
   Austria

   Phone: +43 1 5056416 34
   Email: alexander.mayrhofer@nic.at
   URI:   http://www.nic.at/


   Christian   Spanring
   5 Crawford St
   Cambridge  02139

   Phone: +1 617 800 7885
   Email: christian@spanring.eu
   URI:   http://www.spanring.eu/































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