previous paragraphs) a selection of the image window
correspondiog to superimposed part of a map sheet should be
carried out. It is possible to do it empirically by comparing
the map with the image hardcopy or with the image on the
display screen. However T this method is not accurate too much
and suitable for larger amount of data.
It is better to select the image windows by means of image
coordinates of the map sheet corners. They can be calculated
by at t ine transformetiert front their - cartographic coordinates.
Results of digital image processing have to be written on the
film, »he film scanner/writer Photomation P 1700 Optronics is
used for this purpose in our laboratory.
the selection of the suitable print components is of special
importance. It Is not good to overfill the photornap by the
cartographic line content, but it is necessary to consider
user s interest . Components for planimetry, geographic names
or water are often used.
The Carl Zeiss Jena precision rectifier Rectimat C was used
for the color photomap production. Color photornap is a color
composite superimposed with selected map print components.
Three color components must be succesively introduced into the
photo carrier of the rectifier and exposed with red, blue and
green filters on the color film.
A map content on the negative of cartographic fair draft is
exposed with white light. Two cases of superimposing are
possible
a) exposure of reduced negatives placed in the photo carrier,
b) exposure of negatives at original scale that are put
straight on the photomaterial on the projection table of
the rectifier.
The second way is less elaborate and gives better legible
cartographic line drawing on the photornap.
C onclusion
The method described has been successfully aopiied at Remote
Sensing Centre of Geodetic and Cartographic Enterprise in
Prague. Several photomaps sheet from North Bohemia and
neighbourhood of Prague have been produced in this way.
References
[ 1 j Charvdt, K., Cervenka, V., Hylmar, F.: Production of
1 50 000 Pseudocolor Photomaps from Thematic Mapper
data. Symposium ICA, Budapest, 1989.
