It is interesting that the stereoeffect is still unexpectedly high if 
images of different pixel sizes are simultaneously interpreted (e.g. one 
50 pm pixel size image observed in stereo with a 200 pm pixel image). 
ADDITIONAL INTERPRETATIONS 
In order to clarify whether the simulated imagery generated by digitiza 
tion of aerial photography is characteristic for the mapping problem al 
so with scanners, additional imagery has been compared: 
Fig.9 shows a geometrically rectified part of a M 2 S image (Bendix scanner) 
at the scale 1:50 000 with an IF0V of 2.5 mrd. together with the 1:50 000 
topographic map. 
Fig.10 shows one stereopair of MBB-E0S CCD-Array pushbroom scanner images 
(ground pixel size: 60 cm, focal length: 24 mm, see Hofmann /4/). These 
stereo-images have additional deficiencies in form of: 
- different scales of the stereomates, 
- missed scan line portions. 
Fig.11 at the scale 1:50 000 showing the Capitol of Washington D.C. com 
pares a microscopic enlargement of a 
- Skylab S190 B first generation copy (original image scale 
1:950 000) 
- a Landsat 2 image produced on the IBM-Laser-Scanner (original image 
scale 1:800 000) 
-an aerial photograph at the original image scale 1:100 000 and 
- part of the city-map (scale 1:50 000). 
The comparison shows that existing photographic images are more than 
competitive with existing digital methods. Enlarged to the scale 1:50 000 
the Landsat-image appears quite blurred. The original Skylab photo is com 
parable with the city map. 
Fig.12 shows a comparison of a SAR 580 optically processed coherent radar 
image over a part of the City of Ottawa with a stereopair and the map at 
the scale 1:50 000. 
Fig.13 is an enlargement thereof. This enlargement' documents the weak 
nesses of the existing Radar imagery; for example buildings'are shown as 
big clots. Radar images have large height displacements. Therefore DTM- 
heights are required to transform the radar image to map geometry. 
Contrary to aerial photography radar images cannot be properly interpre 
ted to derive all required topographic features even though radar images 
show many other features such as metallic objects (fences, power lines, 
vehicles). It is questionable if the topographic use of radar imagery is 
even possible for the map scale 1:250 000. Radar images can therefore 
only serve as supplementary information. 
Fig.9: Freiburg (Red.Rep.Germany, scale 1:50 000 (by courtesy of DFVLR))