1103 
UP TO DATE DSM GENERATION USING HIGH RESOLUTION SATELLITE IMAGE 
DATA 
K. Wolff*, A. Gruen 
Institute of Geodesy and Photogrammetry, ETH Zurich 
Wolfgang-Pauli-Str. 15, CH-8093 Zurich, Switzerland - (wolff, gruen@geod.baug.ethz.ch) 
Commission I, ThS-3 
KEY WORDS: Satellite remote sensing, Digital surface models (DSM), Digital photogrammetry, Accuracy analysis, Stereo 
capabilities 
ABSTRACT: 
Due to the increasing costs of high resolution satellite image data with stereo capabilities, products like accurate DSMs are becoming 
attractive for more and more users and applications. The Japanese optical sensor ALOS/PRISM which was launched in January 2006 
has stereo capabilities by providing a simultaneous acquired image triplet. We have published several results of our evaluation of the 
potential of ALOS/PRISM image data together with our powerful software packages SAT-PP (Satellite Image Precision Processing) 
for DSM generation. Here, we focus on a new aspect, namely on the potential of the use of the image triplet in comparison to the use 
of just a stereo image pair, e.g. the combination of FN and FB. As we will see improves the use of a third image the results of the 
DSM generation especially for the combination of FB, but also for the combination FN. Additionally we will present the evaluation 
results of a new testfield, the volcano Sakurajima in Japan. The special characteristics of the volcano surface are very difficulty 
conditions for the image matching and DSM generation. 
1. INTRODUCTION 
Due to the increasing costs of high resolution satellite image 
data with stereo capabilities, products like accurate DSMs are 
becoming attractive for more and more users and applications. 
Satellites with just one lens capture stereo images with a time 
delay, e.g. Ikonos and WordView-1. Satellites with two or more 
lenses can capture quasi simultaneously stereo images, e.g. 
Cartosat-1 with a forward and an aft view or ALOS/PRISM 
with the triplet forward (F), nadir (N) and backward (B). 
As a member of the validation and calibration team for 
ALOS/PRISM we focused among other topics on the DSM 
generation and its evaluation. We have published several results 
of our evaluation of the potential of ALOS/PRISM image data 
together with our powerful software packages SAT-PP 
(Satellite Image Precision Processing) for DSM generation. For 
details about the testareas and the evaluation results see Gruen 
et al. (2006), (2007) and (2008) and Wolff and Gruen (2007). 
The software has been tested successfully for processing of a 
number of high resolution satellite sensors, such as IKONOS, 
QuickBird, ALOS/PRISM, and SPOT-5 HRS/HRG and is 
meanwhile close to operation. Detailed information on the 
SAT-PP and its functionalities can be found in Zang and Gruen 
(2004), Zang (2005) and Gruen et al. (2005). 
Here, we focus on one hand on the potential of the use of the 
image triplet in comparison to the use of just a stereo image pair, 
e.g. the combination of FN and FB. As we will see improves the 
use of a third image the results of the DSM generation 
especially for the combination of FB, but also for the 
combination FN. 
Additionally we will present the evaluation results of a new 
testfield, the volcano Sakurajima in Japan. The special 
characteristics of the volcano surface are very difficulty 
conditions for the image matching and DSM generation. 
Therefore the results of the DSM generation are less good as the 
results of other testareas. 
2. IMAGE DATA 
Radiometric problems of ALOS/PRISM image data like black 
reference calibration (resulting in striping), jpeg-compression 
(resulting in blocking), saturation effects (mainly related to only 
8-bit radiometric depth collection), and others were already 
discussed. For details about the radiometric problems see Gruen 
et al. (2007). 
JAXA proposed a new processed version of the early 
ALOS/PRISM imagery with less striping. The use of these new 
processed images is beneficial for visualization purposes. 
However, the reduction of the striping does not has any 
significant influence on georeferencing and only a local 
influence on the DSM generation, but not on the height RMSE 
over all. 
The three views of ALOS/PRISM which we will use in 
different combinations do have the following viewing angels: - 
23.8°, 0°, 23.8°. 
3. DSM GENERATION 
The main component of our powerful software package SAT- 
PP is the matching algorithm for the DSM generation. The 
procedure is based on a multi-image Least-Squares Matching 
(LSM) for image features like points and lines. The image 
matching approach uses a coarse-to-fine hierarchical solution 
with an effective combination of several image matching 
methods and automatic quality indication. In addition to the