ACCURACY OF SUPERIMPOSITION 
A. van Voorden and M. van Persie' 
Delft University of Technology, 
Faculty of Geodetic Engineering, 
Thijsseweg 11, 2629 JA Delft, 
The Netherlands 
ABSTRACT: Superimposition can in principle be used for the detection of errors in coordinates of features 
which are stored in a database. 
For the error detection three aspects are important: 
1. The width of the lines which are superimposed on the aerial photograph(s). 
2. The accuracy of superimposition through the whole stereomodel at the position of the measuring mark. 
3. The accuracy of superimposition through the whole field of view of the binoculars. 
For each of these aspects a testing method has been developed. The test procedures have been used to test 
three superimposition systems, which are built in analytical plotters of different companies. 
In the paper characteristics of the tested superimposition systems are given. The testing methods will be 
described and the results will be presented. 
KEY WORDS: Accuracy, superimposition, algorithm, data base, data quality. 
1. INTRODUCTION The developed tests and the test results are 
described in chapter 3. In chapter 4 conclusions 
Superimposition means the projection of a digital and recommendations are given. 
topographical database on one or two photos in the 
stereo restitution instrument, which implies that 2. SUPERIMPOSITION PRINCIPLE AND 
photo and data base of an area can be viewed sim- SUPERIMPOSITON SYSTEMS 
ultaneously. 
A short description of superimposition and some Superimposition is based on the following prin- 
characteristics of superimposition systems will be ciples: 
given in chapter two. 1. X, Y, Z coordinates of features stored in the 
database are transformed with the formulas of 
In practice superimposition is mostly used to check perpective projection to the geometry of the 
if the features which are stored in the database are photo. For the transformation are used the 
complete and actual. projection centre coordinates and rotations of 
the photo on which the database has to be 
The aim of the research described in this paper is to projected. 
determine the superimposition accuracy of different 2. The transformed database is imaged on a 
systems. When the accuracy is known conclusions screen. The screen image is projected via a 
can be drawn to which extend the detection of data system of lenses and mirrors on the photo 
base errors is possible. For the determination of this image. 
accuracy important are: 
1. The superimposition accuracy at the position of In figure 1 (Bonjour, 1988) the superimposition 
the measuring mark through the whole stereo principle is shown. 
model. 
  
2. The superimposition accuracy around the mea- 
suring mark through the whole field of view. 
3. The width of the superimposed lines. 
Operator eyes ; ux 
Optics for zoom manification, 
image rotation, focusing and 
squint-error correction 
    
To investigate the above mentioned aspects at the 
Delft University of Technology testing procedures Mass 
have been developed (Van Persie 1991). HB -— 6 
The tests are used to determine the superimposition 
accuracy of three systems. Reduction 
These systems are the I.M.A. system of Intergraph, Optics Injection 
the DSR 15 with the Kriss superimposition system EH prism -H 
of Leica (Kern) and the P3 with the videosystem of 
the Zeiss Company. 
Injection 
raster 
screen 
  
  
  
  
  
" Present address: National Aerospace Laboratory Figure 1. Stereo superimposition system 
(N.L.R.), Emmeloord, The Netherlands (Bonjour 1988). 
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