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ermined 
by the Chair of Photogrammetry and Remote Sens- 
ing, Technical University of Munich. The orientation 
is estimated by a bundle solution for three-line im- 
ages, in which a large number of tie points together 
with 56 of ground control points is introduced. The 
first results (Kornus et al., 1995) have been summa- 
rized above. In the meantime a certain improvement 
was achieved by this group so that for the recent ori- 
entation an accuracy level of 6 to 8 m in all three 
coordinates is expected. 
2. DTM GENERATION 
For DTM generation with MOMS stereo images a fea- 
ture based procedure was proposed by Hahn and 
Schneider (1991). In the meantime a matured soft- 
ware module is developed which is highly efficient in 
processing three-line images (Schneider and Hahn, 
1995). The trinocular stereo solution consists of the 
following steps: (1) Image pyramids are generated 
for all channels and matching is started on a coarse 
resolution level of the pyramid. Processing then pro- 
ceeds from coarse to fine with (2) the extraction of 
interest points and edge points; (3) the matching of 
corresponding features of all three channels using 
given orientation; (4) the determination of 3-D point 
coordinates; and (5) surface reconstruction by finite 
element modelling. 
DTM generation is performed with scene 17 of the 
Australia orbit 75B. An area of about 14.5 km x 14.5 
km, in which the DTM evaluation profile can be seen, 
is shown in figure 4. 
fence 
  
fence 
jou 4: Ortho-image of an area of 14.5 km x 14.5 
m 
269 
In this figure an ortho-image is displayed that is calcu- 
lated from the forward looking channel. The markings 
"fence" indicate a very long straight line, presumably 
of a grazing fence. Along this fence there is a track on 
which the 3-D profile is recorded. This track is visible 
in the image (see figure 5). 
  
  
Figure 5: Detailed view: the track along the fence can 
be easily recognized. 
A perspective view of the derived DTM is shown in 
figure 6. In this case the ortho-image is overlayed to 
enhance the visual impression of the terrain surface. 
Because of the very flat terrain the height component 
is amplified by a factor of 20. The grid width of this 
DTM is 240 m. 
3. INVESTIGATION OF THE DTM ACCURACY 
So far the experimental investigations of the geomet- 
ric accuracy in MOMS DTM reconstruction have been 
very limited due to the lack of sufficient ground truth 
data. The test field for evaluating the metric perfor- 
mance of the stereo module (figure 2) was quite use- 
ful for the analysis of sensor models and line-image 
orientation but of very limited evidence in assessing 
DTM accuracy. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996