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' SPIE, Vol.
DIGITAL STEREOPLOTTER FOR HISTORIC MONUMENTS RECORDING
Jozef J. Jachimski, Janusz M. Zielinski
The Department of Photogrammetry and Remote Sensing Informatics
University of Mining and Metallurgy
Al. Mickiewicza 30, 30-059 Krakéw, Poland
jjachim@uci.agh.edu.pl
Commision V Working Group 4
KEY WORDS: Close Range, Architecture, Restitution, Digitization, Instruments, Stereoscopic Processing Systems,
Digital Stereoplotter Structure
ABSTRACT
It is hoped that PC-insatiable digital stereoplotter, equipped with several special functions indispensable or just
advisable for easy evaluation of historic monuments and sites, would become a standard tool of restoration teams. The
conditions of such a system design are discussed in the paper.
1. Introduction
The explosion of analytical stereoplotters which took
place at the ISPRS Congress in Helsinki in 1976 opened
before photogrammetric science and practice the
possibility of plotting numeric maps in real time in a
continuous way. It was even possible to make use of
photographs taken with nonprofessional cameras.
Procedures have been developed which support the
operator during evaluation.
However the analog nature of images made it difficult to
automate the stages of plotting, thus the system of an
analytical plotter was supplemented with a set of
television cameras and later with CCD which gave
access to the image around the measuring mark in the
form of an electronic signal or in digital form. This
facilitated an automatic analysis of images and allowed
autocorrelation procedures to be introduced. Photogram-
metry was becoming an universal, reliable and every less
exclusive method owing to the computer support availa-
ble to the operator during preparation and vectorization of
the model.
Unfortunately the high price of analytical plotters was still
making a true egalitarization of the method difficult.
Rapid development of personal computers in the late 80s
was a big step on the road of reducing the elitarian
nature of photogrammetry. In that time, on the basis of
PC, we developed at the Department of Photogrammetry
of AGH both the software for differential plotting of
photographs (presented at the Congress in Kyoto)
[Jachimski 1988] and the system for vectorisation of the
content of a photograph on the screen. Our investigations
into vectorization of stereoscopic models on the screen of
the PC monitor were outdistanced by DVP [Agnard 1988,
Gagnon 1990] successfully.
A true explosion of new system for vectorization of
stereograms on the screen of a computer monitor took
place at the ISPRS Congress in Washington in 1992
[Klaver 1992, Miller 1992, Jachimski 1992]. Excellent and
Very costly systems, which-permit the screen to be
simultaneously observed by several persons, were and
still are impressive. The stereoscopes used by the teams
259
in Quebec and Cracow were replaced by the dynamic
system Crystal Eyes and static polarizating spectacles.
This required, however, very costly computer solutions to
be applied.
The excellent and complicated systems overshadowed
the simple and cheap solutions based on the use of PC
and mirror stereoscope. However it proved soon that
much cheaper and simpler (and thus less perfect)
systems DVP from Quebec and VSD from Cracow did
not loose their popularity and that due to their price and
utilization advantages they have found more and more
new users, and student laboratories at universities have
been equipped with multistation VSD networks.
The high cost of solutions adopted by Intergraph or Leica
is a consequence of the necessity to visualize on the
screen of a working station alternatively the left and right
image of a stereogram and to operate with the same
frequency of 50-100 Hz the viewing system which
enables selective observation of the corresponding
images with the left and right eye. In 1994 the firm
Galileo-Sicam in Florence and the Technical University of
Torino presented a static viewing system [Dequal 1994]
based on the use of two monitors observed selectively
correspondingly with the left and right eye through
polarizating spectacles. The Italian system is considera-
bly cheaper and at the same time not inferior to the
dynamic system.
User's interest in digital stereoplotters has not lessened
and designs based on mirror stereoscopes have been
ever wider introduced. For instance the firm Leica already
distributes its excellent digital working station DPW 770
(Helawa) [Leica 1994a] in its dynamic-spectacles version
and in the static version equipped with a Mirror
stereoscope (DPW 670 [Leica 1994b]). More and more
copyrighted software packages for digital stereoplotters
based on PCs and mirror stereoscopes have appeared.
Thus the concept of that system does not loose its
attractiveness and software solutions based on standard
computers can be developed and improved without any
additional cost of hardware.
Precision of plotting performed with the aid of digital ste-
reoplotters depends mainly on the geometrical precision
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996
