6.- Working Methods
The working procedures for the revision of the Topographic Map 1:25 000 differ conside-
rably with the individual State Survey Offices. They depend on the data and instruments available,
the scale of aerial photographs, as well as on the tradition in the office concerned.
6.1. Revision Based on Large Scale Basic Maps
Figure 1 shows the work flow of this pro-
cedure. In accordance with the revision pro-
gramme established for a long-range period,
the photo flight is planned. In areas, for which
the German Basic Map 1:5 000 could not be re-
vised and where extensive changes have taken
place, aerial photographs at 1:12 000 scale are
taken. Based on these photographs, the corres-
ponding sheets of the German Basic Map 1:5 000
are revised by the local offices inthe simpliest
manner. Âs far as aerial photographs were taken
they have been rectified and enlarged to 1:5 000
scale, so that the changes can be taken off di-
rectly. Localfield checking for the German Ba-
sic Map 1:5 000 is also made by the localoffices.
In very rare cases only, aerial photographs are
stereoscopically restituted by the central State
Survey Office.
The sheets of the German Basic Map
Continuous revision of the German Basic Map
1:5 000 concerning buildings and status of owner-
ship by local cadastral offices
Photo flight 1:12000
Topographic revision of the German Basic Map
1:5000 in regular intervals with field checking
and by means of enlargements of aerial photo-
graphs 1:5000 by local cadastral offices
Reduction to 1: 25000 scale of the revised
German Basic Map 1:5000
Preparation of a revision manuscript 1:25000
according to the reductions of the German Basic
Map 1:5000
rer M ERR e:
1:5000, revised in such a way, are reduced to
1:25 000 scale and then a complete revision ma- $
Revision of the
Topographic Map
Revision of the
Topographic Map
nuscript 1:25 000is prepared. Fromthis manus- + 20000 i
cript a colour copy can be made, so that the ori- hE IT Ai
ginals of the Topographic Maps 1:25000 and
7 eventually. second field checking |
1:50 000 can be revised simultaneously.
Cr fs ob
eventually inclusion
of the results of field
checking into
1:50000 scale
Since at least 2 years have passed after
the photo flight and the field check respectively,
it is mostly necessary in both cases to add im-
portant modifications, as e.g. road construc-
tions as "individual corrections"'.
eventually inclusion
8 of the results of field
checking into
1: 25000 scale
In a later paragraph, this procedure will
be compared withthe direct revision of the To-
pographic Map 1:25 000.
Revision of the Topographic Map 1: 25000 by Means of the
Basic Map with Special Revision Manuscript
(Procedure |)
6. 2. Revision Predominantly Based on Single Aerial Photographs
If aerial photographs shall be applied in a really rational manner to the revision of maps
at different scales, then the "photo-on-map techniques' should be always used. The aerial photo-
graph and the model respectively should be superimposed on the map or, a direct comparison
should be possible. By such a method, all modifications can be recognized immediately.
When single aerial photographs are used, these are rectified or projected and simulta-
neously brought to the drawing scale. A simple instrument, the Antiscope, is partly used for pro-
jecting. By means of this instrument the aerial photographs are projected into the map to be re-
vised, the areas to be revised are correctly placed and plotted. By means of this instrument aerial
photographs can be 05. to 6.5 times enlarged without steps. Consequently, aerial photographs at
very different scales can be used. In order to secure a sufficient interpretation, the 1:24 000 photo-
scale is preferred and corrections are made at 1:10 000 scale, i.e. on enlargements of the Topo-
50 —
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