International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
USAGE OF STEREO ORTHOIMAGE IN GIS:
OLD CONCEPT, MODERN SOLUTION
K. Pyka*, M. Slota?, M. Twardowski *
* Dept. of Geoinformation, Photogrammetry and Remote Sensing of Environment,
Faculty of Mining Surveying and Environmental Engineering, AGH University of Science and Technology,
Krakow, Poland - krisfoto@agh.edu.pl
Commission IV/II, WG IV/1,4,5, 11/2,6,8
KEY WORDS: Photogrammetry/GIS, Visualization, Orthorectification, Stereoscopic
ABSTRACT:
The main goal of this paper is to find answer for two questions: why stereo orthoimage (orthophoto) was forgotten, and furthermore,
what conditions have to be fulfilled for this particular technique to be reanimated?
Stereo orthophoto concept was first introduced by Collins, during late seventies of last century (Colins, 1968). It has ignited huge
interest, and many researchers were looking forward for its development (Blachut 1976, Kraus et al. 1976). However, after around
twenty years, interest in stereo-orthophoto has shrunk, and during eighties of XX century it was almost extinct. Despite of fact that
digital photogrammetry provides better conditions for it now than ever, it has never got chance for reactivation. There was but few
papers about stereo orthoimage, and they are proposing continuous stereo ortho-mosaic generation while preserving its metric value
(Li et al 2002, Wang 2004).
Reasons of downfall of this interest were examined, and it has been concluded that the main cause was usage of this technique in
conjunction with analog photogrammetry. The radiometric value of orthophotomaps and stereo components developed on
photosensitive paper were very low during that time. Equipment for observation and measurement were simply very big and
therefore impractical. Authors have concluded, that nowadays sum of gains outweighs its flaws and it is reason enough to go back to
it But in a time of digital vector 3D models there is a need for proper strategy for popularization stereo orthophoto.
Main point of this strategy would be encapsulating stereo orthoimage method into GIS tools, optimally open source. GIS have large
numbers of consumers whom regard for orthophotomap (or orthoimage) is very high. If they were to be proposed with possibility of
using stereo orthoimage inside a GIS tool, as a complementary to the orthophotomap, probably they would recon how much
stereoscopy helps with interpretation of an image.
Authors have planned to develop software for utilization of stereo orthoimage available from the Quantum GIS interface, and test
version is to be based on anaglyph stereoscopy. Value of creating continuous stereo-mosaic composed from many 3D models was
assessed. Consensus was, however, that this solution surprises us with frequent perspective changes which leads to discomfort. As an
outcome it was decided to focus on single stereo orthoimage pairs. When area constrains are specified for single model, one can load
them as requested by an user. In case of increased lateral and longitudinal coverage, which is more common in modern aerial
photogrammetric flights, every localization will be accessible for visualization using several models, and there will be less concealed
areas.
Few algorithms for generation of parallax are tested. After completion of sets from a dozen or so example models of interesting areas
are gathered, there will be release. Authors are confident that stereo orthoimage may prove more useful for GIS users than true
orthophotomap.
1. INTRODUCTION attempts to return to the stereo orthophoto technique with a
greater emphasis on GIS applications have been made(Li et al
The concept of stereo orthophoto technique published by ^ 2002, 2009, Wang, 2004, Chang et al 2008). While orthophotos
Collins 44 years ago (Collins, 1968) quickly became a subject have been firmly established in the GIS environment, stereo
of research and implementation. A number of devices with 3D orthophotos are still scarcely used.
stereo orthophoto measurement capabilities have been built.
Accuracy of those devices has been tested (Real et al 1974, The purpose of this article is to present possibilities of broader
Jachimski 1978, Kraus et al 1979) and possible application use of the stereo orthophoto technology in GIS. According to
areas have been indicated (Blachut, 1971, 1976). However after the authors ,the original Collin's and Blachut's idea to
about 10 years, further development of the stereo orthophoto introduce the stereo orthophoto to the wide range of users is
technology had been discontinued, probably because of the worth reinstating. It could be achieved by strong technique
occurring disadvantages, such as very large size of measuring implementation in the GIS technology.
devices or poor quality of available photographic materials.
These disadvantages discouraged potential users, which would
have been architects, geologists, foresters, topographers, etc. 2. STEREO ORTHOPHOTO PRINCIPLES
This slightly forgotten technique was reinstated in the 90s, :
when GIS had been already well developed (Sarjakoski, 1990, The term stereo orthophoto refers to the pair of images, where
Baltsavias, 1996, Li et al 1996). In the last decade some visible one of the images is a classic orthophoto and the other one 15 2
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