The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part BI. Beijing 2008 
the edges of the shadow area. For the other shadow areas we 
found similar effects. 
5. DISCUSSION AND CONCLUSIONS 
We have validated DSM generation using ALOS/PRISM 
image data over two testfields. For the Bem/Thun testfield 
we focused on the comparison of using the image triplet in 
comparison to the use of just two views (here FN and FB). 
With the testfield Sakurajima we gave new results of our 
work as a member of the validation and calibration team for 
ALOS/PRISM. 
The results of our first test confirm what we expected: in 
comparison to the RMSE of the FNB combination of we got 
instead ofa5.5m-6.6ma less good accuracy for the FN 
combination with 6.4m - 7.5m and for the BF combination 
even 6.6m - 9.3m. The worst results were obtained for the 
sub area Southwest with an alpine area included. Over all is 
the RMSE less than 4 pixels. For a detailed analysis we 
visualized three example areas with their shaded DSM. It 
was shown that valleys disappear using the FB combination 
and mountains loose their structure. 
The performance of PRISM imagery in connection with our 
multi-image matcher of SAT-PP was tested for the new 
volcanic testfield Sakurajima (largely open volcanic terrain). 
The height RMSEs for the testfields are all between 2 to 5 
pixels for the raw matching results without any post 
processing for blunder removal. These results are in the 
range of what we can expect from high resolution satellite 
image data. Additionally, we defined within the sub-areas of 
Bem/Thun, areas of specific and homogeneous 
topographic/land use characteristics (open space, city, forest 
and alpine) in order to test the DSM generation quality in 
dependence of these parameters. The height RMSE values 
ranged from 4.7 m (open areas) to 12.8 m (forest). This 
corresponds to a height accuracy of 2 - 5 pixels. Although 
these values look quite good, we must note that there are still 
too many blunders in the data, which are not acceptable for 
mapping tasks. These blunders appear mainly in shadow 
areas what we analyzed for one example in detail. 
For the Bem/Thun testfield we had also a new version of the 
image data with less striping. We detected only a small local 
influence on the DSM generation which will be analyzed in 
detail in the future. The height RMSE did not change overall. 
However, for visualization purposes the image quality of the 
new images is improved. 
If we compare these results of DSM generation with those 
which were obtained with other satellite sensors of similar 
type (SPOT-5, IKONOS, Quickbird) we note that the 
accuracy (expressed in pixels) is about the same. 
A critical point for future research has to be the detection 
and/or avoidance of blunders in the automatically generated 
DSM. 
ACKNOWLEDGEMENTS 
The authors would like to thank Kokusai Kogyo Co. Ltd. for 
providing the reference DSM. 
REFERENCES 
Gruen A., Zhang L., Eisenbeiss H, 2005. “3D Precision 
Processing Of High Resolution Satellite Imagery”, ASPRS 
2005 Annual Conference, Baltimore, Maryland, USA, March 
7-11, on CD-ROM. 
Gruen A., Kocaman S., Wolff K., 2007. “Calibration and 
Validation of Early ALOS/PRISM Images”, The Journal of 
the Japan Society of Photogrammetry and Remote Sensing, 
Vol 46, No. 1, 2007, pp. 24-38. 
Gruen, A., Murai, S., Baltsavias, E., Kocaman, S., Wolff, K., 
Hanusch, T., 2008. „Investigations on the ALOS/PRISM and 
AVNIR-2 Sensor Models and Products2”. Interim PI Report 
for JAXA. 
Gruen, A., Eisenbeiss, H., Hanusch, T., Sauerbier, M., Wolff, 
K., 2006. “Documentation of the reference DSMs of the 
ALOS testfield Bem/Thun”, Report to JAXA. 
Wolff K., Gruen, A., 2007. “DSM Generation from early 
ALOS/PRISM data using SAT-PP”. High-Resolution Earth 
Imaging for Geospatial Information, Proceedings of ISPRS 
Hanover Workshop. 
Zhang, L., 2005 “Automatic Digital Surface Model (DSM) 
Generation from Linear Array Images”, Ph. D. Dissertation, 
Report No. 88, Institute of Geodesy and Photogrammetry, 
ETH Zurich, Switzerland. 
Zhang L., Gruen A., 2004. “Automatic DSM Generation 
from Linear Array Imagery Data”, International Archives of 
Photogrammetry and Remote Sensing, 35(B3), pp. 128-133. 
Zhang, L., Gruen, A, 2006. “Multi-image matching for DSM 
generation from IKONOS imagery”, ISPRS Journal of 
Photogrammetry and Remote Sensing, Vol. 60, No. 3, 
pp. 195-211.