ALOS Global Digital Surface Model (ALOS World 3D - 30m)
The AW3D30 product is created by the stacking process with multiple data observed from 2006 to 2011.
Therefore, it is not possible to uniquely identify the observation timing.
For AW3D30 v2.1 and later versions, the observation date and time of the data used is indicated in the included "LST file".
The AW3D30 product is created with the following definitions.
Digital Surface Model (DSM), elevation from height above sea level (in meter) converted from the ellipsoidal height based on ITRF97 coordinate system and GRS80 ellipsoid, using EGM96 geoid model.
The latitude and longitude in the file name means the coordinates of the lower left corner of the lower left pixel of the image.
Please note that SRTM and ASTER GDEM have different definition.
The following figure shows the outline of the difference between AW3D30 and ASTER GDEM grid.
The value of the elevation of each pixel is a representative value at the center position of that pixel.
We have no DTM product. EORC creates only DSM as AW3D30.