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I have a very simple kml file written as xml format:

<?xml version="1.0" encoding="utf-8"?>
<kml xmlns:kml="http://earth.google.com/kml/2.2">
  <Document id="featureCollection">
    <Style id="defaultStyle">
      <LineStyle>
        <width>1.5</width>
      </LineStyle>
      <PolyStyle>
        <color>7d8a30c4</color>
      </PolyStyle>
    </Style>
    <Folder>
      <Placemark>
        <styleUrl>#defaultStyle</styleUrl>
        <ExtendedData>
          <Data name="innerwater">
            <value></value>
          </Data>
          <Data name="shape_len">
            <value>0</value>
          </Data>
          <Data name="shape_are">
            <value>0</value>
          </Data>
          <Data name="perimeter">
            <value>0</value>
          </Data>
          <Data name="sde_sfgis">
            <value>0</value>
          </Data>
          <Data name="objectid">
            <value>1</value>
          </Data>
        </ExtendedData>
        <MultiGeometry>
          <Polygon>
            <outerBoundaryIs>
              <LinearRing>
                <coordinates>      
    -122.33333333333333,37.83333333333333 
-122.33333333333333,37.70000000000000 
-122.53333333333333,37.70000000000000 
-122.53333333333333,37.83333333333333 
                </coordinates>
              </LinearRing>
            </outerBoundaryIs>
          </Polygon>
        </MultiGeometry>
      </Placemark>
    </Folder>
  </Document>
</kml>  

From the coordinates, you can easily understand that the used datum is WGS-84. But I've been searching the kml documentation for about an hour now and I can't find any tag for datum definition.
Does that mean KML files just support coordinates reported in WGS-84? (I know that google earth coordinates are in WGS-84)
If not, then how a geospatial software will understand what's the datum used? And which formulas should be used to project it on the map?

4

Quoting from here which seems to be a copy of the standard but not in PDF.

KML relies on a single Coordinate Reference System, which is not referenced explicitly in KML files. The encoding of every kml:Location and coordinate tuple uses geodetic longitude, geodetic latitude, and altitude (in that order) as defined in Annex A of the KML specification by the GML Coordinate Reference System (CRS) with identifier LonLat84_5773. The vertical datum, used for altitude measurements is the WGS84 EGM96 Geoid.

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  • 3
    Note: in the 2.3 international standard. the CRS information is mainly in annex B which mentions that the 2D portion is based on 4326 (WGS84). – mkennedy Aug 4 '16 at 17:38

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