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stereoscope. Because of the lack of DOVE prisms the 
images have to be resampled to epipolar geometry, which 
is being done using the high speed GTP. The control of 
the image movement in x,y,z and the selection of processing 
functions is done via a 3-button optical mouse. Giving the 
operator the possibility to move either with x,y-plane or 
z-direction, but not simultaneously. Digital elevation data 
(DEM) can be automatically generated by the use of digital 
correlation implemented on a specific filter processor 
(GOP). An example is shown in Figure 2. 
Figure 2: Overlay of contour lines as correlated by the 
automatic DTM-generator 
3. DESIGN AND CONSIDERATIONS FOR FUTURE SYSTEMS 
As mentionned earlier the development of a DPW based 
on a standard image processing hardware is restricted in 
many ways, because in most cases the standard hardware 
architecture of image processing systems does not meet 
all operational requirements of a DPW. As an example the 
feasibility of image painting devices, such as mouse, trackball, 
joy-stick etc in most cases is not sufficient for controlling 
movements in all three coordinate directions, a fact which 
very often is neglected. Three other critical components will 
be looked at in more detail in the following sections.