Having downloaded and compiled the ASTER GDEM data-set for the entire African continent (~ 3,300 tiles), we present a short summary of our initial analysis of the data here.

The quality of the DEM derived from ASTER images is strongly affected by cloud anomalies and overall quality of the individual scenes. There are therefore some notable problems with the ASTER GDEM, including many pits, spikes and mole-runs. 

The figure on the right shows an example from the eastern rainforest of Madagascar, where we have spikes that are >5,500 m. Also included in the figure is a profile (red) based on SRTM-90. We have also found pits that are > 1000 m deep, and numerous anomalies particularly in the Sahara and Sahel (i.e. flat areas). Also, many mountain peaks and ridges are lost in the data.

As stated in the GDEM documentation, elevation postings in the ASTER GDEM are at 1 arcsecond, or approximately 30 m, but the detail of topographic expression resolvable in the ASTER GDEM appears to be between 100 m and 120 m.

Version 1 of the ASTER GDEM must therefore be viewed as experimental or research grade.