REVISION DES CARTES 
gt werden, MAP REVISION BY ORTHOPHOTOGRAPHY 
nd, her- 
en in 
t des Dr.-Ing. O. WEIBRECHT 
! VEB Carl Zeiss JENA 
r dann 
st aus- 
anken- Given the rapidity at which our globe changes its face today, any newly compiled map 
icher will inevitably be the subject of recurrent revision in order to remain up to date. It is not surpri- 
es sing that photogrammetry, apart from being used at large for mapmaking, should come handy as 
a means for map revision as well. 
Any cartographic institution using photogrammetric methods, then, will have to reserve 
a certain percentage of its production capacity to the updating of existing maps. This raises the 
question as to the kind of equipment to be used for revision jobs. Basically, there are two possi- | 
bilities : Map revision may share the instrumentation provided for the compilation of new maps or 
be carried out on special equipment. Decision between the two ways depends upon several factors, 
including the extent of revision jobs, the rate of utilization of the equipment provided for map com- 
E pilation, the scales of the maps to be revised, and the investment and operating costs involved. i 
The latter aspect is of particular importance in map-revision, where the relation between compi- Ir 
lation and orientation times is different from that in the production of new maps. Strictly speaking, | 
the area compiled per shift will be less for map revision than for new maps. These facts are cogent i] 
reasons for the employment of unsophisticated, budget-priced equipment and the application of cost- ï 
saving techniques. | 
Orthophotography, with its inherent economizing and productivity-increasing potential, I 
has become increasingly popular as a means of map compilation. There is no reason to forbear i 
using this technique for map revision, and the less so as a high-performance, simple and universal 
system is available for the purpose - the Topocart-B/Orthophot-B made by VEB Carl Zeiss JENA 
1:25 000 ee. 0. 
l'échel- The substantial preponderance of information content in a photomap over that in a graphic 
sungs- map is not the least argument for orthophotography as a means of map revision. Moreover, the 
d'un results of orthophoto map revision not only serve the topographic task in hand, but can also supply 
mploie useful information for special-purpose maps and other branches of science. Employment of the 
eipour Topocart-B/Orthophot-B combination for map revision allows mapping in large, medium and 
small scales. When used in on-line operation, the system merits low cost, high productivity, 
superior quality, convenient operation, and a high degree of automation. 
zahl An analysis of all known orthophoto methods will reveal that on-line operation in general 
rto- offers some advantages for map revision jobs. To arrive at objective conclusions, identical condi- 
t die tions should be assumed for all methods so analysed. Equipment cost, being one of the criteria to 
. be assessed, should be rated equal for similar pieces of equipment. Productivity as another cri- 
ingsamt terion can be characterized by the number of process operations required. Reliability and accuracy 
on are suitable criteria to assess the quality obtained by a particular method. The criterion of man/ 
hoe machine interaction can be analysed in terms of operational economy and comfort, the extent of 
operator attendance required, and the extent of automation. Special aspects that may vary from 
user to user should be left out of account, such as the different functional principles and different 
prices of comparable units. 
An analysis of that kind was carried out for the following methods of producing new or 
000° updating existing orthophoto maps : 
1.- on-line method, successive orthophotography and contour mapping ; 
mme- 2. - on-line method, simultaneous orthophotography and contour mapping ; | 
3. - off-line method using stored analogue profile data ; I 
4. - off-line method using stored digital profile data ; | 
5. - off-line method using stereo orthophotos ; 
6.- mixed method using stored digital contour data, with off-line orthophotography and on-line 
contour mapping ; 
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