Re: [dhcwg] Fwd: Working Group Last Call: Location Configuration

To all:

As someone who has been working on location referencing for Intelligent
Transportation Systems for years for the USDOT ITS standards program, I
have been following with interest the recent discussion in this group on
datums. FYI, what follows is a set of extracts from a new SAE standard
about to go to ballot (ATIS committee), called the Location Referencing
Message Specification (LRMS). The LRMS specifies data concepts and
messages for a variety of coordinate based and non-coordinate based
location referencing methods. Note in the extracts that much of what you
have been discussing is in the standard. With respect to units, altitude
is in 'Distance' units, which are a choice of integer or real expressions
for different English and Metric units. A complete XML Schema is part of
the standard, and I would be glad to provide the complete draft to members
of this group who would be interested in being official reviewers of the
standard.

Also related to the discussion on WGS-84 and ITRF, an ISO TC204 sub-working
group is developing an international location referencing standard for ITS
location referencing between navigation databases. While this standard is
not complete, ITRF has been accepted as the standard geodetic datum, being
more acceptable to our non-US members than WGS-84.

Dr. Cecil W. H. Goodwin
1564 Blue Heron Ln
Jacksonville Beach, FL 32250
Phone/Fax: 904-246-2264
Email: cwgoodwin@earthlink.net

--------------- excerpts --------------

5.15 Data Frame: GeoLocation:frame

Use: The GeoLocation sub-profile conveys a two- or three-dimensional
geographic location. The standard horizontal datum for a spot location is
WGS-84; other horizontal datums can be specified by
HorizontalDatum. Vertical Datum is an option within height.

ASN.1 Representation:

GeoLocation ::= SEQUENCE {
      latitude Latitude,
      longitude Longitude,
      horizontalDatum HorizontalDatum OPTIONAL,
      height Height OPTIONAL
          }

------------------------------------

5.26 Data Frame: Height:frame

Use: A vertical height expressed as either an altitude with respect to a
vertical datum, or a vertical level from -7 to +7, where level 0 is the
ground surface, or ground level of a structure.

ASN.1 Representation:

Height ::= CHOICE {
    altdatum SEQUENCE {
       altitude Distance,
       verticalDatum VerticalDatum OPTIONAL
                       },
    verticalLevel VerticalLevel
        }

--------------------------------------

6.17 Data Element: HorizontalDatum:cd
Use: The underlying horizontal geodetic datum for a geographic coordinate.

ASN.1 Representation:

HorizontalDatum ::= ENUMERATED {
  wgs-84 (0),
  wgs-84egm-96 (1),
  nad83 (2),
  nad27 (3)
  }

------------------------

6.59 Data Element: VerticalDatum:cd

Use: The underlying vertical geodetic datum for a geographic coordinate.

ASN.1 Representation:

VerticalDatum ::= ENUMERATED {
        wgs-84 (0),
        navd (1),
        ...}

---------------------------

6.60 Data Element: VerticalLevel:qty

Use: Vertical level specified as an ordinal class expressed positive
(above) or negative (below) the ground surface or ground level of a
structure. (vertical level code = 0).

ASN.1 Representation:

VerticalLevel ::= INTEGER (-7..7)

XML Representation:
<xs:simpleType name="VerticalLevel" >
       <xs:restriction base="xs:byte">
          <xs:minInclusive value="-7"/>
          <xs:maxInclusive value="7"/>
       </xs:restriction>
</xs:simpleType>

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Received on Thu Jul 10 11:38:34 2003