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OEEPE RESEARCH PROJECT AEROTRIANGULATION USING DIGITIZED IMAGES 
FINAL RESULTS 
Juha Jaakkola and Tapani Sarjakoski 
Finnish Geodetic Institute, Finland 
Commission Ill, Working Group 2 
KEYWORDS: Digital, Triangulation, Automation, Photogrammetry 
ABSTRACT: 
Aerial triangulation using digital imagery has been investigated as an OEEPE test using a large scale photography 
( 1:4000 ) over a small town. The participants performed block triangulations using digital images of 15 um and 30 um 
pixel sizes and different methods and systems for measuring image coordinates. The adjusted ground coordinates were 
compared with geodetic coordinates. The results showed in comparison with accurate analogue methods the high 
potential of digital imagery in aerial triangulation. 
1. INTRODUCTION 
The development in computer science and technology as 
well as in photogrammetric research has gradually 
brought digital photogrammetry to a stage, where 
practical applications are becoming a reality. Especially 
such applications, which do not require complicated 
image understanding, are already possible. Aerial 
triangulation using digitized images ( DAT ) is one of 
these applications. 
In aerial triangulation the digitalisation of the system 
brings several advantages: 
e The image remains stable after the scanning process. 
Therefore no deformations can occur during the rest 
of the process. Also the use of orientation parameters 
in the mensuration phase is possible without any loss 
of accuracy. 
e The high level of automation makes it possible to 
measure more points than in analogue systems. 
Therefore the effects of different image errors can be 
reduced. Gross errors can be detected more easily, 
systematic errors are better controlled, and the effects 
of random errors on adjusted values are smaller. 
e Automation allows faster throughput and better 
economy. 
Digital systems naturally have also some drawbacks, 
when compared to conventional technics. One of them is 
the loss of image quality due to digitizing. The resolution 
will be worse, and in the spectral range some errors can 
easily occur, even if the digital methods allow advanced 
image enhancements. 
Only a few results from limited experimental tests on 
digital aerial triangulation has been available, so 
Commission A ( Aerotriangulation ) of the European 
Organisation for Experimental Photogrammetric Research 
( OEEPE ) has organised a project, starting 1993, to bring 
more general knowledge about this area. The systems, 
which were available three years ago, were still mainly of 
an experimental nature. Therefore the scope of the test 
was limited to accuracy aspects of DAT. The operational 
side of the systems, very important itself, has been left 
out. 
The purpose of the test was to get information about the 
potential of DAT and its special features, like the effects 
of pixel size, measuring resolution and method. The 
comparisons to conventional methods were also needed. 
More complete results have been reported in the OEEPE 
official Publication No 31. 
  
Figure 1. Forssa test block and the signalised ground 
points. Black triangles mean XYZ- and 
white triangles XY-points. 
349 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
  
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