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exposure, the general diapositive is placed in perfect register with the same sheet and
exposed for a longer time. The gnide which now appears after development, shows two
tints again: black and grey. Now only the houses are shown in grey. These houses are
engraved now, taking into account the widened roads as well. By doing so the engraving
'red' is produced. As the process of engraving 'brown' for the contour lines is a simple
matter it is not necessary to go into details here.
In order to obtain a first proof of the three separate engravings diapositives are made
of each of them, and from these diapositives a colour proof is made by copying on a
sheet of astrafoil. On this proof the corrections are marked, which have to be carried
out by the engraver in the original engravings. Next a combined photographic diapositive
'black-blue-red' is made, of course on dimensional stable film on polyester base, which
serves as a guide for the Stripping of the füll colours. This guide is copied onto a
sensitized sheet of 'peelcoat' stabilene. After an exposure the lines are dissolved by
etching. This procedure is repeated for every füll colour that has to appear on the map:
one 'peelcoat' for meadow, one for wood, one for land blue, etc. etc..
Taking the 'peelcoat' for meadows as an example, on this sheet all those areas, to be
printed in the green colour for meadows, are stripped off. These stripped parts are
shown as transparant open areas on the light table.
As previously explained: in the etching process all the lines of the combined guide
are dissolved by etching. But these lines must not appear in colour and therefore they
have to be made opaque. To prevent this time-consuming work the following method
is applied: as soon as the 'peelcoat' has been etched the whole image is covered with a
black dye. Notwithstanding this dying, the parts for the meadow colour can be stripped
off.
To the separate engravings and 'peelcoats' have to be added the films with map
lettering and grid, which do not fall within the scope of this article.
A second proof is made, again by producing a combined copy in colour on astrafoil,
on which corrections are marked.
Next several combinations from separate sheets which have to be printed from one
zinc plate are made. As an example the 'blue' plate is chosen. The line drawing for
blue, the stripped 'peelcoats' for land blue and sea blue and the blue grid numbers have
to be combined. This is effectuated by using the negatives of these separate sheets.
Contact copies of these separate negatives are superimposed on each other. To guarantee
a perfect registering, the sheets have been provided beforehand with punch holes. This
Operation, of course, must be done with the utmost accuracy.
When the combined diapositives have been produced in this way, the final step in
the cartographic process is to copy them on zinc or aluminium plates after which print-
ing can Start.
For the sake of clarity the description of the various Operations has been kept as
simple as possible.
The new cartographic process has caused great alterations as well in technique as in
Organization. For example: it will be obvious that photographic Operations have gained
upon copying. This yields the advantage that the quality of the photographic image is
not diminished after the successive Operations, as in copying. At this stage one cannot
yet speak of routine in the new cartographic process of the Topographie Service. That
will be achieved in years to come.
But is seems desirable to comply with the request made by the Cartographic Section
of the K.N.A.G. to introduce now at the present time, modern cartography in general
and the application of it by the Topographie Service in particular, to colleagues and.
persons interested.
