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7. - Comparison of Procedures 
With the present requirements to be met by our maps, it is no longer possible to revise 
the individual map series subsequently and then to start with the largest scale. On the day of their 
publication the small-scale maps would already be obsolete because the changes had been consi- 
dered several years ago. Therefore, in many organizations the tendency exists to revise the maps 
of the different scales, or better of certain scale groups, independently of each other. 
  
In the State Survey Office of Northrhine-Westphalia nowadays a small test has been made 
in order to check whether or not it will be economic first to revise the two maps of 1:25 000 and 
1:50 000 scales in common, but independently of the Basic Map 1:5 000. 
One sheet of the Topographic Map 1:25 000, for which considerable and extensive modifi- 
cations existed, had to be revised. This sheet was completely covered by sheets of the German 
Basic Map 1:5000, showing the recent state. These were partly symbol maps, partly aerial photo 
maps. Furthermore, aerial photographs at 1:35 000 scale were available which had been taken at 
the same date as the photographs for the aerial photo maps 1:5 000. 
This sheet of the Topographic Map 1:25 000 has been revised completely and independently 
of each other according to the Basic Maps 1:5000 (Fig. 3, procedure II) as well as also according 
to the aerial photographs 1:33 000 (Fig. 4, procedure III). A Planicart E 2 has been used for the 
plotting of the aerial photographs. For this reason only procedures II and III can be compared in 
detail. 
At first, it must be stated that for procedure II the extensive works for the revision of 
the Basic Map sheets had not been taken into consideration. In order to make the comparison pos- 
sible, we have furthermore not taken into account that it can hardly be attained to up-date at a j 
certain date all sheets of the German Basic Map 1:5 000 (about 120) which cover the area of one 
sheet of the Topographic Map 1:50 000. 
Moreover, in procedure II, contrary to procedure I no special revision manuscript is 
prepared. The modifications are directly taken over from the sheets of the German Basic Map 
1:5 000 into enlargements 1:10 000 of the Topographic Map 1:25 000. Compared with procedure I, 
with procedure II a considerable amount of working time is saved. For procedure II therefore, we 
have assumed optimal conditions which are not always attainable. In spite of this, the expenditure 
of time with procedure III is slightly, and the costs are by more than 10 % smaller than those of 
procedure II (fig. 5a). Thus, procedure III with the direct revision by means of aerial photographs 
is considerably more economic than procedure I, for which a special revision manuscript 1:25 000 
is prepared, and still some more economic than procedure II. It has the advantage, in the same 
way as procedure I, but contrary to procedure II, that it is possible to revise the two map series 
1:25000 and 1:50000 nearly simultaneously. 
But, on the other hand, there is the disadvantage that with procedure III the greatest part 
of cartographic work (69 days) must be done after field checking. The above requirement that field 
checking should be done to the advantage of up-to-dateness at the end of the work flow, can thus 
only be met partially. 
Certainly favoured by the strong magnification (4, 18 times) in the Planicart, a very 
reliable interpretation is possible (Fig. 5b). Only as to communication lines and single symbols, 
the percentage of correct acquisition is relatively small. The number of single symbols is small 
and of minor importance for map information. Therefore, the relatively small percentage of the 
unequivocally interpreted single symbols is not essential. The course of the lines of communica- 
tions had always been plotted, but partly their classification was missing. This information can 
certainly be collected by inquiries before plotting, so that it is possible, not only to plot new com- 
munication lines reliably, but also to classify them correctly and to draw them by the pertaining 
symbols. On the whole, in this photogrammetric plotting with new photographic material, more 
than 90 % of all modifications can reliably be interpreted, so that immediately after completion 
of plotting, field checking as well as the cartographic work of correction can be started at 1:25 000 
and 1:50 000 scales. Above all, with the direct revision by means of aerial photographs we are 
independent of the revision of the German Basic Map 1:5 000 by the local cadastral offices. Conse- 
quently, considerable administrative work is avoided which is difficult to be calculated and there- 
fore has not been taken into account. 
. 59.