ALTITUDE_ABSOLUTE mode: MSL or WGS84 geoid?

[Phil Vandry]

The documentation for the Google Earth API states that when using the
absolute altitude mode (ALTITUDE_ABSOLUTE), values are taken relative
to [mean] sea level:

http://code.google.com/apis/kml/documentation/altitudemode.html#absolute

Is there any other information available about what this corresponds
to? Is it WGS84/ECM96?

I compared a random sampling of 22 points in the USA with SRTM data (I
used USA in order to be able to use the 1 arc-second SRTM data), it's
pretty close to what Google Earth reports (average discrepancy of 4.6
metres). The SRTM data uses WGS84/ECM96:

http://dds.cr.usgs.gov/srtm/version2_1/Documentation/SRTM_Topo.pdf

-Phil

[fraser (Earth API Guru)]

Hi Phil,

AFAIK all versions of Google Earth use simple cylindrical projection
with a WGS84 datum for the imagery base.
See: http://earth.google.com/userguide/v4/ug_importdata.html#note

Hope that helps,

Fraser.