The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
Statistical analysis of IKONOS and ALOS DEM shows a 
standard deviation around 4.0 meters which is consistent with 
ALOS PRISM DEM expected accuracy and IKONOS known 
altimetry accuracy. When partionning this statistical analysis 
between mountainous area and plain areas, we end-up with 
standard deviation around 2.3 meters for plain area, and 5.2 
meters for mountainous area. Those results are consistent with 
other reports (Wolff K. and all, 2007) available in the scientific 
literature about PRISM derived DEM. 
Statistics 
# points 
Bias (m) 
RMS 
(m) 
Global 
539670 
0.28 
4.07 
Mountains 
271110 
0.13 
5.24 
Plains 
269465 
0.43 
2.34 
Table 1 : Height accuracy of PRISM DEM 
Due to the limited size of our overlapping reference dataset, it 
was not possible to conduct this statistical analysis all over the 
area. Nevertheless, the overall DEM shows a consistent 
rendering of the landscape without major artifacts, except those 
already mentioned. 
Figure 8: Overlay of PRISM orthoimage with PRISM DEM 
5. CONCLUSION 
Despite the quality of initial input images, it is possible to 
extract globally accurate dense terrain elevation information 
from PRISM data. However, some local artifacts are still 
preventing from precise local stereoscopic measurements which 
are only overcome by merging multiple elevation information 
derived from the different views of PRISM triplet acquisition. 
Variations have been measured inside the resulting DEM and a 
more systematic analysis of multiple PRISM acquisition is 
certainly needed in order to assess rigorously origins of such 
vibration. 
The software package used for this validation process named 
Pixel Factory proves its robustness as generated Digital 
Elevation Model had few blunders, even with strong 
radiometric artifacts inside the input PRISM images. All results 
shown in this article were done on full automated extracted 
DEM, without any manual filtering. 
REFERENCES 
Frank Bignone. Processing of stereo-scanner: from stereo 
plotter to Pixel Factory. Photogrammetric Week, Stuttgart, 2003 
Wolff K., Gruen A. DSM Generation from early ALOS/PRISM 
Data using SAT-PP. ISPRS Hannover Workshop 2007, "High 
Resolution Earth Imaging for Geospatial Information", 
Hannover, Germany, May 29- June 1, 2007. 
Tadono T., Shimada M., Watanabe M., Hashimoto T., Iwata T. 
Calibration and Validation of PRISM Onboard ALOS, 
International Archives of Photogrammetry and Remote Sensing, 
Vol.XXXV part Bl, pp. 13-18, 2004. 
JAXA, http://www.eorc.jaxa.jp/ALOS/, 2007