5 48 150 
XI11 Congress of the 
International Society for Photogrammetry 
Helsinki, 1976 
Commission V 
Invited Paper 
ORTHOPHOTOGRAPHY IN ARCHITECTURAL 
PHOTOGRAMMETRY 
by 
E. Seeger 
Institute for Photogrammetry 
Stuttgart University 
(FRG) 
T. Introduction 
The usually practiced technique for graphic representation of 
architectural objects is the photoarammetric stereoplotting. This 
method has been found to be accurate and applicable to objects of 
any type, shape and size. The result of stereoplotting is a line 
map which shows the recorded object in the form of elevations and 
plan views. 
The efficiency of the method, however, becomes questionable, if 
richly decorated or painted surfaces must be plotted. The time 
expenditure for stereoplotting increases rapidly with the quantity 
of details. Therefore it is possible that analoque plotting of 
baroque fresco-paintings or classicistic facades requires draft- 
ing times, for example, of several weeks per model. This problem 
demands other representation techniques, especially for the appli- 
cation of continuous-tone processes. 
In some institutions elevation maps of facades were produced by 
rectification or simple enlargement of photographs. |f the objects 
are extended in depth, radial displacements caused by central pro- 
jection are found in the off-axis areas. So rectification methods 
can only be applied to plane or almost plane surfaces. A better 
adaptation to the object is made possible by improving the degree 
of rectification. Separate transformation of parts and zones of 
the object can reduce the displacements, but causes detailed 
mosaic-works. 
In the revision process of topographical maps a method for differ- 
ential conversion of central-perspective photographs to an approxi- 
mate parallel projection has been applied for years. |t can be