interest point 
tion about its 
ilized to build 
n is taken ei- 
tal data, from 
calculated. As 
to the elliptic 
he image into 
et of transfor- 
gate points is 
osen high, the 
e but not very 
1 to receive a 
"irst, the con- 
y is improved 
rmann 1983). 
eed points for 
pends on the 
pyramid level 
ng should not 
ns in order to 
The pyramid 
plexity of the 
of only a few 
igher pyramid 
quares match- 
ned only once 
ere one pixel 
). 
are chosen ap- 
erated by least 
the conjugate 
mid level and 
"his step is re- 
he number of 
ninated on dif- 
hin the image 
new matching 
age sets have 
3-line scanners 
amera. For all 
tie points per 
  
  
  
  
  
  
  
  
  
  
  
Figure 3: MEOSS images from the forward-looking (upper), nadir-looking (middle), and aft-looking (lower) CCD arrays 
with conjugate points (flight direction is from left to right) 
3.1 MEOSS 
In Figure 3 images from a rural scene are displayed. They 
were taken by MEOSS (Monocular Electro-Optical Stereo 
Scanner) during an airborne testflight in 1989. Each image 
has a size of about 8400 x 3200 pixel and a ground pixel 
size of 2.0 m. 
1771 conjugate points — superimposed in white — were 
found, which are well distributed across the overlapping 
area. The region growing has been performed at pyramid 
level 4 with a step size of 6 pixel. 
A bundle adjustment was carried out to check the match- 
ing accuracy and the number of remaining gross errors. 
The results indicate an accuracy of the image coordinates 
of 0.2 pixel, and less than 3% of the image points were 
detected as gross errors. 
3.2 MOMS-02/D2 
In Figure 4 two images from the Egyptian desert taken 
by the 3-line camera MOMS-02 (Modular Optoelec- 
tronic Multispectral Stereo Scanner) are depicted. The 
MOMS-02 scanner was flown on the Space Shuttle dur- 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
ing the German D2-Mission in April/May 1993. The im- 
ages have been acquired from the nadir looking arrays at 
different orbit arcs with slightly different flight directions 
(~ 5°). The ground pixel size amounts to 4.5 m in both 
images. In this example, region growing was performed at 
level 5 of the image pyramid. Due to poor texture in parts 
of the images in combination with the high level for the 
region growing, only a few points could be found. 
To improve the result, we started a second region growing 
at pyramid level 3. This leads to a very dense distribution 
of conjugate points (Figure 5). In regions with very little 
texture, however, no points were determined. 
To demonstrate the improved performance of the new ap- 
proach, we applied least squares matching with region 
growing solely on pyramid level 0, which leads to inad- 
equate results (Figure 6). Note that initial values and 
control parameters were identical to those of the new ap- 
proach. 
3.3 VIKING 
Figure 7 represents a pair of stereo images from planet 
Mars, taken by a Vidicon frame camera from the VIKING