Subject: [Geopriv] [geopriv] #32: Appendix B

From: "geopriv issue tracker" <[email-masked]>
Date: Fri, 05 Mar 2010 06:27:58 -0000

#32: Appendix B
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 Reporter:  bernard_aboba@…            |       Owner:  martin.thomson@…          
     Type:  defect                     |      Status:  new                       
 Priority:  major                      |   Milestone:  draft-ietf-geopriv-3825bis
Component:  rfc3825bis                 |     Version:  1.0                       
 Severity:  Active WG Document         |    Keywords:                            
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 See Martin's post:
 http://www.ietf.org/mail-archive/web/geopriv/current/msg08343.html

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/geopriv/trac/ticket/32>
geopriv <http://tools.ietf.org/geopriv/>

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From: "geopriv issue tracker" <[email-masked]>
Date: Sun, 07 Mar 2010 21:51:36 -0000

#32: Appendix B
---------------------------------------+------------------------------------
 Reporter:  bernard_aboba@…            |        Owner:  martin.thomson@…          
     Type:  defect                     |       Status:  closed                    
 Priority:  major                      |    Milestone:  draft-ietf-geopriv-3825bis
Component:  rfc3825bis                 |      Version:  1.0                       
 Severity:  Active WG Document         |   Resolution:  fixed                     
 Keywords:                             |  
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Changes (by bernard_aboba@…):

  * status:  new => closed
  * resolution:  => fixed

Comment:

 I substituted the text in Appendix B.1, leaving B.2 alone.  Some of the
 original material in Appendix B.1 appeared important in understand the
 encoding (such as information on how the Altitude was determined), so I
 left that in.

 Here is the text of Appendix B and B.1 as it appears in -09:

 Appendix B. Calculations of Resolution

    The following examples for two different locations demonstrate how
    the Resolution values for Latitude, Longitude, and Altitude (used in
    the version 0 DHCPv4 option) can be calculated.  In both examples,
    the geo-location values were derived from maps using the WGS84 map
    datum, therefore in these examples, the Datum field would have a
    value = 1 (00000001, or 0x01).

 B.1.  Location Configuration Information of "White House" (Example 1)

    The grounds of the White House in Washington D.C. (1600 Pennsylvania
    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
    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
    inside a structure, we assume an Altitude value of 15 meters,
    interpolated from the US Geological survey map, Washington Washington
    West quadrangle.

    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
    easily identifiable location on our planet.

    In this example, the requirement of emergency responders in North
    America via their NENA Model Legislation [NENA] could be met by a
    LatUnc value of 21 and a LongUnc value of 20.  This would yield a
    geo-location that is Latitude 38.8984375 north to Latitude 38.8988616
    north and Longitude -77.0371094 to Longitude -77.0375977.  This is an
    area of approximately 89 feet by 75 feet or 6669 square feet, which
    is very close to the 7000 square feet requested by NENA.  In this
    example, a service provider could enforce that a device send a
    Location Configuration Information with this minimum amount of
    resolution for this particular location when calling emergency
    services.

   An approximate representation of this location might be provided using
   the version 0 encoding as follows:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Code (123)  |  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|0 0 0 1 0 0 1 1 0 1.
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                Latitude (cont'd)              |  LongUnc  |   .
     .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)                      |
     .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 |   AltUnc  |                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.
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .  Alt (cont'd) |Ver| Res |Datum|
     .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.

 Decoding Location Configuration Information with Resolution

    Decoding this option gives a latitude of 38.897647 (to 7 decimal
    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
    and 17 bits of resolution; version 0 (resolution) and the WGS84
    datum.

    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
    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
    values in the range from 0 to 32 meters.

 GML Representation of Decoded Location Configuration Information

    The following GML shows the value decoded in the previous example as
    a point in a three dimensional CRS:

     <gml:Point srsName="urn:ogc:def:crs:EPSG::4979"
                xmlns:gml="http://www.opengis.net/gml";>
       <gml:pos>38.897647 -77.0366 15</gml:pos>
     </gml:Point>

    This representation ignores the values included in the resolution
    parameters.  If resolution values are provided, a rectangular prism
    can be used to represent the location.

    The following example uses all of the decoded information from the
    previous example:

   <gs:Prism srsName="urn:ogc:def:crs:EPSG::4979"
       xmlns:gs="http://www.opengis.net/pidflo/1.0";
       xmlns:gml="http://www.opengis.net/gml";>
     <gs:base>
       <gml:Polygon>
        <gml:exterior>
           <gml:LinearRing>
            <gml:posList>
               38.8964844 -77.0390625 0
               38.8964844 -77.0351563 0
               38.8984375 -77.0351563 0
               38.8984375 -77.0390625 0
               38.8964844 -77.0390625 0
             </gml:posList>
           </gml:LinearRing>
         </gml:exterior>
       </gml:Polygon>
     </gs:base>
     <gs:height uom="urn:ogc:def:uom:EPSG::9001">
       32
     </gs:height>
   </gs:Prism>

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Ticket URL: <http://trac.tools.ietf.org/wg/geopriv/trac/ticket/32#comment:1>
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