We did a comparison between the free 90m posting SRTM DEM data and the new 5m posting DSM data of IFSAR/NEXTmap Malaysia. The test data covers an area of 5km x 5km over a forested and rural area of Sabah. Both are surface data (i.e. DSM) .
The result is shown above in color shaded relief map as the subtraction (the diffrences in height/elevation in meters) between the two surfaces.
The relative accuracy of the two surfaces is about 24m at 95% confidence level. The relative vertical height diffrences between the two surfaces at some locations are as high as -56m and +54m. (i.e. extreme differences of over 100m).
We think the result provides useful guide to users who want to use 3 arc second SRTM DEM data for their terrain analysis and related works.
Acknowlegement: IFSAR data set contributed by Intermap Technology Inc