PSEUDO-STEREO DIGITAL PHOTOGRAMMETRY 
Eugene E. Derenyi and Ying Chen* 
Department of Geodesy and Geomatics Engineering, University of New Brunswick 
P.O. Box 4400, Fredericton, N.B. Canada E3B 5A3 
* Now at The Department of Geomatics Engineering, University of Calgary 
Calgary, Alberta, Canada T2N 1N4 
Commission II, Intercommission Working Group II/III 
KEY WORDS: Digital photogrammetry, Image matching, GIS, Digital mapping. 
ABSTRACT 
À so called pseudo-stereo technique was developed for soft-copy mapping which allows spatial 
positioning without the need for stereo viewing or a digital elevation model. Digitization is 
performed monoscopically on the display screen of a computer graphics workstation in one of 
the images of a stereo pair. Corresponding points in the second image are located by area based 
least squares image matching. The object space coordinates are then computed by space 
intersection. A close initial approximation of the matching position is assured by enforcing the 
epipolar geometry as a constraint and by an a priori estimation of the elevation of the feature to 
be mapped. This mapping technique was successfully implemented and tested in a commercial 
geographic information system. 
1. INTRODUCTION 
Soft-copy, digital photogrammetry is 
revolutionizing map compilation. The 
production of general purpose basic maps, 
such as the federal, provincial or municipal 
map series, will probably remain in the hands 
of professional mapping organizations in the 
foreseeable future. Natural resource 
inventory maps, thematic maps, special 
purpose maps, and alike can now be 
produced by professionals and technologists 
in various disciplines, who are also the users 
of these products. With the help of mapping 
software, these individuals can extract, in a 
computer graphics workstation, the 
information they need from digital images. 
Extensive knowledge in photogrammetry and 
cartography is no longer necessary. This 
desk top mapping is analogous to desk top 
publishing which is now widely applied. 
The first commercial versions of all-digital 
photogrammetric restitution instruments 
appeared in the 1980s, and several models 
were exhibited at the 1992 ISPRS Congress. 
Currently, the high performance workstations 
are rather expensive, and are affordable only 
by large organizations. There are also some 
technical problems to be overcome before 
soft copy images replace the diapositive. 
More powerful processors, larger and faster 
memories, higher resolution display screens, 
and the development of a CCD camera with a 
performance comparable to a cartographic 
aerial film camera are needed. Electronic 
technology is advancing at a rapid pace, thus 
it will not take all-digital photogrammetric 
systems thirty years to come to age, as was 
the case for the analytical plotters. In the 
meantime, attention should be focused on the 
so called secondary mapping operations like, 
resource inventory, thematic, customized 
mapping and map updating. Existing 
technology can serve these applications well, 
in a cost effective manner. 
Secondary mapping is performed under 
different conditions and requirements than 
primary basic mapping, in the following 
respects: 
*  Planimetric information extraction is the 
main goal. 
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