Design and Implementation of a Digital Photogrammetric System. 
D.J.Gugan and I.J.Dowman 
Department of Photogrammetry and Surveying 
University College London 
Gower Street 
London WC1E 6BT 
Abstract 
The launch of SPOT in 1986 wil provide the first 
opportunity to fully exploit the advantages of a digital plotter, to 
extract topographic map data directly from digital imagery. 
The essential features required of a digital stereo plotting 
system are real-time scanning of the whole model area, sub-pixel 
measurement accuracy, three-dimensional floating mark control and of 
course, stereo viewing. 
These capabilities can be incorporated into specially 
designed systems based on known technology, but existing image 
processing systems can also be programmed to function as a digital 
plotter with a minimum of additional hardware. 
This paper describes the design requirements and problems 
inovlved with developing a working digital stereo plotter based on an 
17S Model 75 image processor at University College London. 
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