The Wild-Raytheon Stereomat A 2000 
by R. M. de Graaf and R. S. Lee 
Introduction 
The Stereomat A 2000 is the continuation of the development started by Mr. G. Hobrough 
when he automated first the Kelsh plotter and later the Nistri photomapper with the Stereo- 
mat correlator. 
In thé Stereomat III the application of differential scan size controls for two separate flying 
spot scanners made better slope handling possible. In the Stereomat IV independent scan 
control for each side was used so that the scan in each flying spot scanner could be adapted 
more accurately to the deformed image on the diapositive. This enabled the extraction of 
true orthophotos in the Stereomat IV. 
Due to the use of the same scan for both orthophoto extraction and correlation, the 
smallest scan size was limited to one that would give an homogenous orthophoto. This also 
made a choice of swath width impossible. Moreover the continuously varying ratio between 
noise and circular scan for optimum correlation and slope handling caused an exposure 
mismatch between adjacent swaths.In order to overcome this limitation the automatic 
correlator function had to be separated from the orthophoto extraction function. This 
could be done by controlling an optical orthophoto printer with an automated stereo- 
plotter. This method has the disadvantage of losing the ability of slope correction; a more 
attractive solution was to create an independent electronic orthophoto extraction loop, 
where the scan can be deformed for slope adaptation, as has been done in the Stereomat 
A 2000. 
Stereomat A 2000 
The Stereomat A2000 has been developed as a joint effort by the Wild company in Heer- 
brugg and the Automatic Raytheon Co. in Alexandria, Virginia. 
The automated stereoplotter is of the mechanical projection type with first order accuracy, 
especially designed for automated production of orthophotos with a resolution of 60 lines 
per mm. Contours can be produced in the form of contour segments exposed independently 
in the x, or y profiling.mode on black-and-white film, or simultaneously on colour film in 
the ortho print mode.