Sixty years Netherlands Society
for Photogrammetry:
an introduction to its celebration
by prof. dr. ir. M. Molenaar, President of the Netherlands Society for Photogrammetry.
The Netherlands Society for Photogrammetry was found
ed in 1932. So in 1992 the 60th anniversary was cele
brated. On this occasion a symposium was organized on
December 16, a day before the birthday of the society's
founder and one of its most celebrated members, the late
Willem Schermerhorn.
In the sixty years of its existence the society has seen big
changes in the field of interest. Originally, the task of
photogrammetry was to speed up topographical mapping
processes. The first hour pioneers developed ingenious
instruments to observe aerial photographs stereoscop-
ically and by optical/mechanical devices they could trans
fer topographical data from the stereo images to map
sheets. Later, the relationship between terrain points and
their photographic image was better understood and
Ir. Jan Timmerman, opening the symposium.
mathematical models were formulated to describe this re
lationship. This theoretical development together with the
advent of modern computers had a major impact on
photogrammetry. It was not any more restricted to its
topographical mapping task, but it provided a high quality
and relatively inexpensive technique for the problem of
point determination in geodesy. At last after a develop
ment of some 50 years photogrammetry became fully
accepted and it was recognised as a full grown land-
surveying technique. This development also made photo
grammetry an important technique for industrial meas
urements.
The advent of modern computers had also an effect on
the mapping tasks of photogrammetry. The mapping
process has been speeded up and the computer assists
366
the operator with consistency checks on the data and the
application of data transformations, etc. Furthermore the
final output of the mapping process is not any more
necessarily a graphical map, but rather a topographical
database. This made photogrammetry an important data
acquisition tool for GIS/LIS-applications.
In this environment the relationship with remote sensing
was established. Both techniques observe the earth sur
face from above, remote sensing emphasizes on the
thematic aspects of the terrain description in the smaller
scale ranges, whereas photogrammetry concentrates
more on the geometrical aspects in the larger scale
ranges. This new relationship has been institutionalized
in the International Society for Photogrammetry and
Remote Sensing (ISPRS) and also in many national
societies. They widened their scope from photogram
metry alone to both photogrammetry and remote sensing
and nowadays also geographic and land information
systems. In the Netherlands, the Netherlands Society for
Photogrammetry joined with the Netherlands Remote
Sensing Society in the Netherlands Federation for Earth
Observation and Geo-informatics.
Although the relationship between these two disciplines
has been recognised, there still appears to be a rather
wide mental gap between the professionals in both fields.
They come from different backgrounds, they work with
different kinds of data which they process in different
environments. The photogrammetrist still obtains his data
basically by stereo viewing aerial photographs and be
cause of his landsurveying background he primarily con
centrates on the geometrical aspects of the topographical
data. This is done on highly specialised equipment that
requires a technique oriented specialist training for the
operator. The remote sensing specialist normally has had
a training in some application discipline and his first con
cern is to extract thematic information from the images
that is relevant for his field of application. This is done
with image processing software installed in normal
computer hardware. In most cases his remote sensing
training is just sufficient for his application and it is hardly
technique oriented.
Though it is to be expected that the relationship between
these two disciplines will become more intrinsic. That is
due to the modern development of photogrammetry
where the aerial images are produced in digital format
like in remote sensing. This means that photogrammetry
will also use image processing software on normal
computer hardware for the production of topographical
data and no longer costly specialised instruments are
needed. Moreover the need for specialist training to use
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