From where were the digital elevation models acquired?  I am interested in the definition of the data.  Do the values correspond to ellipsoid-geod separation, or to height above mean sea level?

David,

We acquired the DEM data that we use from the MODIS Project.  A good source of information would be Robert Wolfe (robert.e.wolfe@nasa.gov).

The elevation values represent terrain height above the geoid.  Since our geolocation accuracy requirements are less stringent than for the MODIS Land products, we ignore the geoid-ellipsoid differences, much as we geolocate our open ocean data to the ellipsoid rather than the geoid.  As you may know, the average difference is about 30 meters, and the maximum is about 100.

Fred Patt

DEMs can be generated from LiDAR data.right now i am working on a LiDAR project and i need to deliver the DEMs..