3. the snow cover and the partly turbid atmosphere reduced the area 
available for point definitions. 
Therefore the orientation was based only on fifteen points, covering 
that part of the model which should be examinated. For the calculations 
the free net adjustment option of MOR was chosen resulting in residuals 
of mar... = 5.0 um in the picture and mqryy = 123 m , mary = 41 m in the 
model. However, the point distribution was not as optimal, so that an a 
posteriori examination of systematic errors seems to be recommendable. 
This was done comparing the DTM-data at single well distributed points 
with the results of a height determination by correlation, with the 
advantage that no more single image points had to be appointed to cor- 
responding ground points. This reduced problems with point selection 
and identification. The results of this examination are plotted in 
fig.!. Obviously the residuals are of systematic character, what attests 
the existence of some smaller errors in the orientation data. Therefore 
later on in the accuracy control, the systematic characteristic of the 
Z-residuals has to be taken into account. 
4, DETERMINATION OF A DIGITAL TERRAIN MODEL 
4.1 Description of the test sites 
Four test sites were chosen with different functions in the investiga- 
tions. 
= Landshut This site covers a major part of the model. With 
208*150 (=31200) equally spaced (500 m) points about 
7710 km” were registrated. Obviosly the purpose of 
this test site is to applicate the correlation onto 
the greater part of the model space, to prove its 
functionality and reliability in determinating a 
great number of points. 
= Deggendorf This site shows very different surface characte- 
ristics. Therefore this area served to differentiate 
between categories like contrast, surface topography 
or object type and to investigate their influence 
onto the quality of the correlation results. The 
determined DTM consists of 900 (30*30) points with 
180 m distance. 
- Vilsbiburg Here we have varying object contents (fields, small 
towns, a small sea, a river, some forests) and lower 
heights differences (about 500 m). The area is 
subdivided into two parts. The first one (Vilsbi- 
burg1) is affected by haze in the atmosphere, while 
the second (Vilsbiburg2) shows only minor atmosphe- 
ric influences. The examination of these test sites 
should show the influence of contrast reduction in 
regions of less complicate topography. Additionally, 
the dimensions of the two DTM (site 1 : 25*25 pts, 
AX=AY=246m ; site 2 : 25%25 pts, AX=AY=490m) could 
give an impression of the influence of varying point 
density. 
- BL =