reliably studied and the results could not be included in the present 
report. We are referring in particular to stereo-orthophotos which were 
only submitted in the spring of 1976 by the Gestalt International Limited. 
The stereo-orthophotos (orthophoto and stereomate) are produced on the 
GPM II in a single operation and from identical height information to meet 
basic economic and technical production requirements. The analysis of 
these stereo-orthophotos will be carried out in a separate study. 
It is hoped that not only present but also the potential users of 
orthophoto products and the industry will find in this publication interest- 
ing and useful information. Certain key factors in the orthophoto process 
were identified and some of their effects quantitatively assessed, an 
indispensable requirement for further advancement in this important 
technique.