All adopted OpenGIS specifications are publicly available and royalty free.
They may be found at www.opengis.org/ogcSpecs.htm . Then go to either
"OpenGISŪ Implementation Specifications" or "Access approved schemas" to
actually download a given OpenGIS specification. Look for GML 3 related
links.

http://schemas.opengis.net/gml/3.0.1/base/direction.xsd

http://www.tschofenig.com/drafts/draft-tschofenig-geopriv-authz-policies-00.txt
http://www.tschofenig.com/drafts/draft-cuellar-geopriv-lo-ml-01.txt
http://www.unreason.com/jfp/ietf/draft-peterson-geopriv-pidf-lo.html


<redefine
  schemaLocation="http://www.example.com/schemas/address.xsd">

  <!-- redefinition of Address -->
  <complexType name="Address">
   <complexContent>
     <extension base="ipo:Address">
      <sequence>
       <element name="country" type="string"/>
      </sequence>
     </extension>
   </complexContent>
  </complexType>

 </redefine>

As well as the GML schema for temporal
(opengis:specification:gml:schema-xsd:temporal:v3.0c6) you might check a
document called OGC Recommendation Paper on Units of Measure Use and
Definition Recommendations
(http://www.opengis.org/techno/discussions/02-007r4.pdf).  This
recommendation paper provides recommendations for use and definition of
the units of measure used for numerical quantities.  These
recommendations are more widespread than OpenGIS only, and are being
proposed at other organizations, including POSC, W3C, CSIRO, PIDX, and
OASIS.  Examples are provided in XML and XML Schema.  This document also
covers angular measurements.  It should be noted that this
recommendation paper references ISO 1000 (base units) and ISO CD 19118
(N1136 - Geographic information - Encoding).  I only mention these
reference as it could provide fundamental definitions for how a location
measurement is encoded in the Location Object (such as angular units)

Nadine Abbott
-------------

For wireless 9-1-1 calls, the geodetic location is provided from the
wireless carriers in a binary coded form over SS7 (ISUP or TCAP/E2,
carried in Calling Geodetic Location parameter; see ANSI T1.628-2000 for
the coding of the CGL--similar, but not the same as the DHCP-LO).  The
location information is processed by an E9-1-1 Database for delivery to
Public Safety Answering Points (PSAPs).  The geodetic location
information that is provided to 9-1-1 Public Safety Answering Points via
queries to these E9-1-1 DBs uses the following NENA formats:

Longitude:
11 bytes; Numeric; 
Longitude/X coordinate.  Right Justified; pad field with zeros to left
of decimal degrees.  +long:  east of Greenwich; -long:  west of
Greenwich.  (Can be used for wireline as well as wireless) Sample: 
+000.######

Latitude 
10 bytes; Numeric; 
Latitude/Y coordinate.  Right Justified; pad field with zeros to left of
decimal degrees.  +lat:  north of equator; -lat:  south of equator. 
(Can be used for wireline as well as wireless) Sample:  +00.######

Elevation 
5 bytes; Numeric;
Elevation/Altitude indicated as height above mean sea level, measured in
meters (Can be used for wireline) Sample: #####

Datum 
2 bytes; alphanumeric;
Specifies the map projection and coordinate system recommended for the
display of the Longitude and Latitude coordinates. Two systems are
commonly used for North America. The code 83 identifies North American
Datum for 1983 (NAD83). Code 84 identifies the World Geodetic System
for 1984 (WGS84). Other codes may be added as additional datum become
available through authorized entities.
Where x =
83 = NAD83
84 = WGS84


Issues lists
http://www.tschofenig.com/geopriv/authz/issues.html


In GML 3.1, position and pos are recommended as the preferred means for
specifying a point. They avoid the format issues of coordinates by
extending a doublelist, so latitude and longitude are both specified as
degrees and decimal degrees, with a single space between elements in the
list. The example as provided in the current GeoPriv draft would change
as follows if using position and pos in place of location and coordinates.

<?xml version="1.0" encoding="UTF-8"?>
    <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:geotarget@example.com">
     <tuple id="sg89ae">
      <status>
       <gp:geopriv>
         <gp:location-info>
           <gml:position>
             <gml:Point gml:id="point1" srsName="urn:EPSG:geographicCRS:4326">
               <gml:pos>37.775 -122.4194</gml:pos>
             </gml:Point>
            </gml:location>
         </gp:location-info>
         <gp:usage-rules>
           <gp:retransmission-allowed>no</gp:retransmission-allowed>
           <gp:retention-expiry>2003-06-23T04:57:29Z</gp:retention-expiry>
         </gp:usage-rules>
       </gp:geopriv>
      </status>
      <timestamp>2003-06-22T20:57:29Z</timestamp>
     </tuple>
    </presence>