and exposure station. All outputs are displayed on a 17" cathode ray tube 
monitor thus assuring comfortable viewing over a relatively wide field. 
The Experimental Double Image Enhancement Viewer was developed 
as an analysis tool for the rapidly rising interpretive technology of 
spectrazonal photography. Previously, each spectrazonal record had to be 
analyzed individually with density differences obtained manually. This 
equipment, however, precisely analyzes the densities on two film records 
simultaneously and presents to the interpreter the densities of conjugate 
images and the density difference between them. Furthermore, these density 
differences may be electronically interpreted by the equipment and played back 
superimposed on the film within selectable thresholds as edge or area en- 
hancements. Such enhancements may be obtained either within a single 
film record or between two spectrazonal film records. 
The possible adaptation of one technology to that of another is 
exemplified in a paper db) written by H. Robert Gribben of the Autometrics 
Division of the Raytheon Company, Alexandria, Virginia, which will be 
distributed during this meeting. Entitled "An Approach to Change Detection", 
the recently developed ortho photo map producing B-8 stereomat is suggested 
as an automatic approach to change detection. As aptly discussed in the 
paper, the subtractive logic of the stereomat stereo image correlator may 
be utilized to compare old and new photographic coverage of an area and 
output as a third ortho photo only change information. 
(11) "An Approach to Change Detection', H. Robert Gribben, Raytheon 
Company, Autometric, Alexandria, Virginia, July 1968. (Paper to 
be distributed at Eleventh International Congress for Photogrammetry.)