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behaviour with intensive testing by production staff and
application specialists with knowledge of the theoretical
foundations of the algorithms." Needless to say that the
theoretical foundations of implemented algorithms are not
always released by the system developers and
manufacturers. Compare also the remarks about DTM
strategy selection in Baltsavias et al., 1996.
4. CONCLUSIONS
In the early years of digital system development a number
of criteria were formulated to express potential advantages
of digital systems compared to analytical plotters:
(1) Increased accuracy
(2) Reduced equipment cost
(3) Increased througput (automation)
(4) Less qualified operators (simple user interface, no or
little stereoviewing)
(b) Faster availability of results (on-line and real-time
processing)
(6) Fast image transmission (use of digital images)
(7) Better quality and more flexible products (combined,
hybrid data)
(8) Better data integration; joint platforms with CAD/GIS
(9) New type of products (image based, visualization,
animation)
While many of these potential advantages have been
realized in close-range systems and applications, the
commercially available systems for aerial photogrammetry
and satellite remote sensing still have plenty of room for
improvement. This is a great motivation for scientists and a
comfort for developers. They both will not run out of work in
the foreseeable future. And as developers are still battling
with the realization of promises yet unfulfilled, new
technolgies, requirements and expectations are rising at the
functionality horizon of digital systems. At larger production
sites the issues of system and component integration and
of logistics become really pressing (Colomer, 1996).
Multimedia technology could provide for new perspectives
for the mostly awkward user interface solutions.
With the ever increasing availability of digital data, in
particular image data, it will become more and more difficult
and demanding to manage flow, storage, accessibility and
retrieval of this information. Content-based image storage
and retrieval techniques have already found wide interest in
various areas of art, science and economy (Computer,
1995). Photogrammetry and remote sensing have yet to
cope with it. Database issues are not only of relevance with
respect to the CAD/GIS connection, but they inherently
have to be addressed when dealing with digital depositories
for both vector and image (pixel) data, which have to be set
up as combined spatial and radiometric information
systems.
We note that the system design and functionality issue of
Digital Stations has somehow been neglected by the
scientific community. As of today we have no comprehen-
sive critical and comparative investigations available. This
leads to the problem that the practitioners have not much
competent support in terms of evaluating systems and
setting up benchmark tests. Experiences are gathered with
purchase decisions already made and systems in place.
In summary, we observe that the prediction, that the
introduction of digital systems radically alters the instru-
mentation and procedures employed, the personnel and
clientele involved and the products generated" (Derenyi,
1995) could not be verified for the mapping community until
today. We rather note a smooth transition from analytical to
digital, with both systems still in use in parallel for a number
of years to come. We realize however one significant
change. This concerns the attitude of students towards
photogrammetry in general. Digital cameras, systems,
processing techniques, and visualization tools proliferate so
much fascination that it does not require too much extra
motivation to attract the young generation to this discipline.
And this is necessary today even more than before, if we
consider the wise and far-sighted words of Paul Rosenberg,
which he coined long before this generation was even born:
„The engineering problems in electronic photogrammetry
are very considerable ... It will be a long time before
completely automatic, electronic photogrammetry is
actually at hand“ (Rosenberg, 1955).
REFERENCES
Ackermann, F., Schneider, W., 1986. High precision aerial
triangulation with point transfer by digital correlation.
International Archives of Photogrammetry and Remote
Sensing, Rovaniemi, 19-22 August, 26(3/1), pp. 18-27.
Albertz, J., Koenig, G., 1984. A digital stereophoto-
grammetric system. International Archives of
Photogrammetry and Remote Sensing, Rio de Janeiro,
25(2), pp. 1-7.
Baltsavias, E., Stallmann, D., 1992. Advancement in
matching of SPOT images by integration of sensor
geometry and treatment of radiometric differences.
International Archives of Photogrammetry and Remote
Sensing, 29(B5), Washington D.C., 2-14 August, pp. 916-
924.
Baltsavias, E.P., Bill, R., 1994. Scanners - A survey of
current technology and future needs. International
Archives of Photogrammetry and Remote Sensing,
Como, 12-16 September, 30(1), pp. 133-143.
Baltsavias, E.P., Li, H., Stefanidis, A., Sinning, M., Mason,
S., 1996. Comparison of two digital photogrammetric
systems with emphasis on DTM generation: case study
glacier measurement. Paper presented to the 18th
ISPRS Congress, Commission IV, Vienna, 9-19 July.
Baltsavias, E.P., Waegli, B., 1996. Quality analyisis and
calibration of DTP scanners. Paper presented to the 18.
Congress of the ISPRS, Commission I, Vienna, 9-19 July.
Beyer, H.A., 1992. Geometric and radiometric analysis of a
CCD-camera based photogrammetric — close-range
system. Ph.D. Thesis, Mitteilungen No. 51, Institute of
Geodesy and Photogrammetry, ETH Zürich.
Brossard, J.-C., 1994. Vergleich manueller und automati-
scher Generierung Digitaler Terrainmodelle anhand von
Testgebieten aus dem Luftbildverband “Lago di
Luzzone*. Diploma Thesis, Institute of Geodesy and
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