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LOW COST SURVEYING SYSTEMS IN ARCHITECTURAL PHOTOGRAMMETRY
Manfred Fellbaum
Institut für Photogrammetrie und Bildverarbeitung
Technische Universitat Braunschweig
FRG
Commission V
0 Abstract
In recent times quite a few new photogrammetric sytems, especially in architectural
photogrammetry, have been introduced to the market. The main difference to the older
existing surveying systems is, that the new ones are not very expensive. This paper tries
to give a survey concerning these low cost systems. It wants to outline the principles of
photogrammetric evaluation, and give some examples.
1 Introduction
This paper gives an overview on existing low
cost photogrammetric systems. The reason for
the coming up of these systems, is the need of
a general accessibility of photogrammetry,
especially in architecture. For many users
conventional analytical plotters are too
expensive. Often, the performance of those
systems is not necessary. There are low cost
solutions required, which are cheap, flexibel,
compatible, versatile, and easy to use.
Therefore all of the systems, which will be
presented in this paper, are menu driven and
use hardware which is compatible to IBM
personal computer and standard plotters. This
overview cannot be complete. The author has
tried to describe different principles by means
of a number of representive systems.
2 Monoscopic Image Measurement
Monoscopic measurement of image coordinates
requires rather simple instrumental devices
(Fig. 2.1), and therefore offers an important
presupposition for low cost photogrammetric
systems. On the one hand, these systems don’t
offer the opportunities of conventional stereo
photogrammetry, on the other hand monoscopic
image measurement fits very much to multi-
image-triangulation, carried out by
simultaneous bundle adjustment. Within the
multi image bundle adjustment a self
calibration of the used cameras can be done.
This increases the reachable accuracy of these
systems and allows the use of non-metric and
partial metric cameras [WESTER-EBBI NGHAUS
1985]. Control information is not restricted to
three dimensionally predetermined object
points. It is possible to introduce geodetic
measurements like distances, directions etc..
Low cost devices for monoscopic image
measurement are high resolution monocomparators
with image carriers for negative film (Fig.
2.2), ‘digitizing tablets (Fig. 2.3), and
computer monitors with digital image processing
hardware (Fig.2.4).
3 Stereoscopic Image Measurement
Due to the stereoscopic viewing of the images,
this kind of measurement requires more complex
measuring instruments than the above mentioned
monoscopic principle. Besides the advantages of
stereo viewing however most of these systems
don't offer the option of a multi image
orientation. This makes simultanous camera
calibration more difficult. If no calibration
is possible at all, only metric cameras can be
used in connection with such a system. The
systems can be divided into stereocomparators
(STC) and analytical plotters. For the latter a
subdivision into Image-Space-Plotters (ISP) and
Object-Space-Plotters (OSP) is possible.
Measurements with either instrument can be done
on an image carrier with negative film, a
digitizing tablet, and a monitor with digital
image processing hardware (Fig. 3.1).
monoscopic
measurement
devices
digitizing computer image
tablet monitor carrier
Fig. 2.1 Devices for monoscopic image
measurement
image carrier
with measuring device
image /
| ANC microscope
| with measuring mark
| — [operator |
image
carrier .—— x y [25r ay
control
Fig. 2.2 Measurement principle of à
monocomparator