lines never Cross and seldom touch each other. Inspection of
some of these regions revealed steep escarpments and cliff-
like slopes on both sides of numerous short ravines, hence
indirectly verifying these situations. It is indeed a surprise that
quality 5-m-contour lines can be measured from stereo imag-
ery with 13.5m ground resolution. This might be seen as evi-
dence for a still higher degree of inner consistency in the or-
der of some 2m standard deviation in height.
The Bolivia scene covers an extremely rugged, highly moun-
taineous terrain of the central part of the Andes in the Rio San
Juan Del Oro region close to the border of Argentina. For this
scene, where ground control could only be derived from an
old 1:50,000 topographic map, identifying suitable and clear
control features both on the map and the imagery turned out to
be a major problem. Planimetric features on the map could
only be identified with an accuracy in the range of 10m to
30m. By virtue of the stereo capability, vertical control could
be identified and measured within a few meters. Therefore,
clearly visible spot heights, particularly mountain peaks, are
extremely well suited for vertical control. This is one of the
advantages of stereophotogrammetry. In this way, 41 control
points could be identified. Their digitized map coordinates
with estimated standard deviations in the order of 0.1mm had
to be transformed from the original UTM grid to a scene-local
topocentric cartesian system. Together with 57 measured tie
points, ORIMOMS succeeded in producing a parallax-free
stereomodel despite the relatively weak datum. Encouraged by
the good results obtained from the Australia stereo scene, we
decided to demonstrate the feasibility of measuring contour
lines in mountaineous terrain. In an area covering some 10km
by 25km and with elevation differences in the order of some
700m, contour lines with 20m interval were measured. The
final plot in Fig. 7 shows a typical Andean north-south run-
ning mountain ridge with a few peaks up to 4,300m altitude,
steep slopes facing west and moderate easterly slopes towards
a flat depression. Captured under PHOCUS, the data base
consists of some 400 individual objects encompassing 255,000
coordinates and requires 2.5 MByte disc space. Visual com-
parison with the contours in the topographic map mostly
showed good agreement.
CONCLUSIONS AND FUTURE ASPECTS
With the presented system, extensive topographic mapping by
means of spaceborne three-line stereo imagery is near at hand.
Map scales of 1:50,000 or larger can be produced by conven-
tional analytical photogrammetry from 1:350,000 image scale.
Although stereocompilation of analog photoproducts derived
from digital image data may be considered an "anachronism",
nevertheless, its high potential for "conventional" mapping
and map revision is obvious - at least as long as purely digital
photogrammetric solutions are still immature or too expensive
for practical work. MOMS is ready for photogrammetric pro-
duction expecting stereo image data to be acquired on the
MIR-Station and made available during the joint Russian-
German MOMS-2P Priroda-Mission beginning in August 1996
545
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
