1:500,000. This mosaic is permanently stored in the GIS.
The Aeronautical Tactical Pilot Charts at a scale of
1:500,000 were the only base map that is available for the
entire region.
The individual scenes with all spectral bands remapped to
a ground resolution of 25 m are stored in GIS usable
format on CD-ROM or Exabyte. Presently the storage of
these data requireds about 12 GB hard disk space in
addition to about 20 rewritable magneto-optical disks (594
MB), Exabyte- and DAT-tapes and CD-ROMs as a
convenient way for data exchange.
Areas of special interest, like the Salar de Atacama, the
Salar de Antofalla or the area around Taltal were
georeferenced and remapped to a pixel size of 25 m,
using Chilean topographic maps at 1:50,000.
For field work the scientists get hardcopies of their
working area at different scales for orientation and a first
interpretation of the geological situation. Special
enhanced images are prepared for detailed interpretation.
The geological interpretation is refined subsequently to
the field work; the results can be digitized on-screen and
input into GIS.
Digital classification concepts were developed simul-
taneously with the visual interpretation for an area
southeast of the Salar de Atacama with a combination of
Landsat, SPOT PAN, and high resolution MOMS data.
For the area of the Salar de Antofalla the utilization of
SIR-C/XSAR in addition to Landsat and SPOT is
investigated.
DEMs from SPOT stereo data
For local neotectonic and morphological investigations,
digital elevation models and orthoimages were created
from SPOT PAN stereo images.
The generation of DEMs from SPOT stereo data is
problematic in this region due to changes occuring in the
images of a stereo pair, originating from the often
considerable time lag between the dates of acquisition. In
the andes, the main problems are snow cover, sand
drifts, clouds, and vegetation changes. Such variations in
the image content result in major areas within a stereo
pair where no image correlation and thus no elevation
extraction is possible.
Systems like the forward- and backward-looking
stereoscopic MOMS-02 will become an interesting
alternative for the future. High quality data of the Andes
were already obtained during the MOMS-02 shuttle
mission. It is expected that the MOMS-PRIRODA mission
from spring 1996 to autumn 1997 will produce a larger
quantity of high-quality data.
CONCLUSIONS
GIS functions provide a powerful means for combined
visualization of different information layers, enabling the
user to conduct contextual interpretation and to "see"
previously hidden connections, e.g.:
e Relationship between gravity residual anomalies and
the geological structure;
e Relations between seismic centers and the structures
at the earth surface;
e Changes in river morphology depending on geology;
e Identification of regional structures from satellite
images.
It was possible to visualize the Benioff Zone from the
collected data of earthquakes or to point out the location
of a concentration of earthquake centers in an inter
ruption of a zone of positive gravity anomalies (area of
the Salar del Rincon, Salar de Cauchari and Salar de
Pocitos). In this area the volcanic belt changes its trend
from NNW to SSE, where it was congruent with the
positive gravity anomaly, to SSW.
For the publication of results the scientists of the different
working groups use the capability of the GIS to present
the data in combination with satellite images as maps or
perspective views.
TREND
After the initial development during the last two years, the
stuctures and the content of the "Andean GIS" have to be
continuously brought up-to-date in order to fulfill its
function as a "common link" between the diverse groups
of scientists. The main task for the future will be the
development of additional applications. As a
complementary tool a Meta-Information System (Kremers,
1994) is being developed to serve as an information
library about the projects, data, results, literature and
cooperating scientists and the progress of the research
project.
ACKNOWLEDGEMENTS
The research described here was conducted within the
special research project (Sonderforschungsbereich) SFB
267. Funding by Deutsche Forschungsgemeinschaft und
Freie Universitat Berlin is gratefully acknowledged.
REFERENCES
Kremers, H., 1994. Umweltdatenbanken.
Marburg, pp. 201-225.
Metropolis,
Srinivasan, A. & Richards, J.A., 1993. Analysis of GIS
spatial data using knowledge-based methods. In: Internat.
J. geogr. Inform. Systems, London, 7,pp. 479-500.
AUTHOR'S ADRESSES
Dr. Kerstin Hofmann
GeoForschungsZentrum Potsdam
Projektbereich 1.5 Remote Sensing
Telegrafenberg A17, D-14473 Potsdam
E-mail: hofmann@gfz-potsdam.de
Prof. Dr. Franz K. List
Freie Universitat Berlin
Inst. f. Geologie, Geophysik und Geoinformatik
Malteserstr. 74-100, Hs. D, D 12249 Berlin
Tel.:+49-30-77 92 570; Fax: +49-30-77 52 075
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
