SELECTIVE RECTIFICATION AND ITS IMPLICATIONS 
By 
Mr. S. Jack Friedman, PE 
O.M.I. Corporation of America 
Alexandria, Virginia, USA 
Two categories of rectification have been commonly discussed 
in photogrammetric literature during recent years. They are the 
conventional rectification of a tilted aerial photograph to a 
condition of zero tilt, that is, parallel to the ground datum, 
and differential rectification which is of such great interest 
these days because of its relationship to orthophotography. 
Each of these two types of rectification meet an important 
need but lack certain features which could be exploited if they 
were made available. Conventional rectification transforms the 
e e aerial exposure to an approximate condition of zero tilt end 
also changes the scale of the photograph but it does not correct 
for the displacements of the photographic image due to relief, 
affine shrinkage, earth curvature or lens distortion. In 
addition, the geometry of the rectified product is similar and 
collinear with the geometry of the original exposure. 
Differential rectification as a process for preparation for 
orthophotographs has been the subject of much recent literature. 
Two proposed ideas, one by Weibrecht and one by Parenti, are the 
most universal and interesting inasmuch as they both employ 
computerized digital techniques, namely, the analytical plotter,