7. - mixed method using stored digital profile data, with on-line orthophotography and off-line 
contour mapping ; 
8.- mixed method using stereo orthophotos, with on-line stereo orthophotography and off-line 
contour mapping. 
As I have to forbear a detailed report of the analysis, let us at least illustrate the result 
of assessing the aforenamed methods (fig. 2). 
The methods were awarded numerical ratings for each criterion, which were added up to 
a Score. It is evident from the graph that on-line methods reach the least number of negative points, 
thus clearly outranking the off-line methods. The higher scores for on-line procedures are accoun- 
ted for by the low investment cost for the equipment employed, the superior quality achieved, and 
the higher productivity. Although off-line and mixed methods rank first as far as operational com- 
fort and the extent of automation are concerned, this is not sufficient to challenge the primacy of 
the on-line methods. 
This analysis provides an objective basis for taking decisions as to the optimal method 
for making of revising photomaps. Naturally, the scores may improve or decline, if other aspects 
relating to a user's specific conditions are taken into account. 
If, for example, the map to be revised shows an area whose ground relief has not changed 
by any building construction work, and, if the map was compiled by off-line photomapping, the 
same method would be justified for revision in so far as the re-use of elevation data stored in ana- 
logue or digital form may provide some economical balance to the higher cost and instrument out- 
lay involved in off-line methods. 
On the other hand, the favourable score of on-line methods can still be improved by using 
the Topocart-B/Orthophot-B system, as the cost, productivity and quality criteria will have extra- 
ordinarily good ratings. 
Reference 
[1] Weibrecht O. - Analyse der Verfahren der Orthophototechnik, Vermessungstechnik 22 (1974) 
6, pp. 201-205 and 22 (1974) 7, pp. 262-266. 
Abstract 
The paper outlines some aspects bearing on the choice of instrumentation for map revision and arguments for 
the application of orthophotography. In an analysis of all known methods.of producing and revising photomaps, assessing 
their costs and values in use, on-line orthophoto methods prove to be the most advantageous, particularly if the Topo- 
cart-B/Orthophoto-B system made by VEB Carl Zeiss JENA is employed. 
Remarque de M. W. Brucklacher 
  
Revision of orthophotomaps means to produce the planimetry completely new ; with the "off-line" method this 
process is very easy because the already existing profile-storage can be used again. Using the double-model system of 
the "off-line" method, complete orthophoto-maps can be produced very fast in comparison to the "on-line" method, with 
which the maps have to be composed of different single orthophotos with the time consuming '"tone-correction' at the 
adjoining corners. Instead of a higher cost due to instrumentation, the 'off-line' method is cheaper that the "on-line" 
method when taking in consideration the reduction of production time. 
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