RÉVISION DES CARTES
THE TOPOGRAPHIC MAP | : 25.000 (PHOTO MAP)
H. SCHMIDT-FALKENBERG
Institut für Angewandte Geodäsie
Frankfurt. a. M.
Nowadays, the preparation and revision (updating) of our topographic map series is essen-
tially influenced by photogrammetry, its photographic and evaluation procedures being extremely
efficient as far as the expenditure of time is concerned. Some unsolved problems as to the prepa-
ration and revision of topographic line maps at 1:10.000, 1:50.000, and 1:100.000 scales by photo-
grammetric procedures have in particular been dealt with by the Commissions D and E of the Orga-
nisation Européenne d'Etudes Photogrammétriques Expérimentales (O.E.E.P.E.) [1] to [4]. How-
ever, aerial photographs not only serve the preparation and revision of line maps but are also used -
after corresponding rectification - as controlled mosaics or as basis for the preparation of photo
maps. In the following, a review is given on the development of the aerial photograph to the photo
map.
1. - Topographic Line Maps or Topographic Photo Maps ?
From the present point of view, the "or' in the question ''Topographic Line Maps or Topo-
graphic Photo Maps’ should better be replaced by an "and". Much could be said about the advantages
and disadvantages of these two types of maps, decisive is, however, that maps only are a reliable
basis for work and decisions if they indicate the "latest" state, i.e. if they are prepared in the
shortest possible time and revised at the shortest possible intervals. Physical planning, regional
planning, environmental protection, administration, economy and commerce, aerial navigation
and navigation at sea, national defence, etc. require up-to-date maps.
In 1970, approximately 222.700 buildings have been constructed in the Federal Republic
of Germany. These buildings would have to be entered into the German Basic Map 1:5.000 and into
the Topographic Map 1:25.000 within a very short period of time if a complete representation of
the built-up areas was to be assured. The question arises whether for such or similar reasons a
combination of line-like representation and controlled mosaic is desirable.
As to the map scale 1:25.000 should be emphasized that many countries of the world do not
yet dispose of topographic map series at this scale and that a high percentage of the existing map
sheets has not been revised for more than 15 years, European countries included.
2. - General Principles on the Cartographic Configuration of Topographic Photo Maps
In topographic maps, the landscape shall be represented in a characteristically simplified
and conceptionally clear manner. Contrary to the generalized line map, the aerial photograph shows
a non-generalized representation of the landscape. Each detail visible from the air - be it topogra-
phically important or not - is photographically (objectively) stored if the resolving power of camera
lens and film, and the size of the respective detail and its contrast to the surrounding still are suf-
ficiently large. Thus an important task in the cartographic configuration of topographic photo maps is
- to arrange the abundance of information contained in the aerial photograph according to topogra-
phic points of view, i.e. to make the photographed landscape topographically evident by graphic
means:
Thereby attention must by paid
- that of the information contained in the aerial photograph as little as possible be made unidenti-
fiable by line drawings to be added and as such cannot be extracted anymore [5] . Although these
demands are easily made, they cannot be as easily fulfilled.
For economic reasons we should finally demand that in the preparation of topographic
photo maps the manual work be kept to a minimum. Otherwise the time gained by applying the
orthophoto method would prove ineffectual.
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