FOTOGRAMMETRIE EN
CARTOGRAFIE
L. VAN ZUYLEN and J. A. VAN DER LINDEN,
A punching machine for accurate register in making
coloured maps
In map making, especially of coloured maps, the maintenance of
register is an important subject.
At the time when topographic maps still were drawn with ink
on transparent sheets such as "astralon" or "astrafoil nearly all
combinations were made by means of the positive copy method.
Then it was possible to put in register the map components in day
light because the copy emulsion is a very hard one and the influence
of daylight on a sensitive sheet was not perceptible after developing.
To secure accurate register of the separate map components cross-
marks in the sheet corners were used. When discrepancies in dimen
sion existed one had to find by eye the mean position of all four
cross-marks to achieve the most accurate combination.
Since about four years the ink drawing method has been aban
doned for the production of the Dutch topographic maps and
scribing on coated polyester "stabilene' sheets was adopted. The
production of combinations of the non-transparent scribed sheets
now had to be performed in the dark room and the problem of
exact register became more difficult.
Starting from the topographic manuscript base map a general
negative I 25,000 on "cronaflex" is derived by reduction, which
contains all topographic features to be shown in the final printed
map. It is the source of the different guide images for colour sepa
ration scribing. When the scribing of the first colour separation (for
the black lines on the map) is finished, the general negative must be
combined with the scribed black plate by a contact process upon
another coated sheet to produce a guide image for scribing the blue
lines.
After the scribing of the blue guide is ready, this sheet has to be
combined again with the general negative and the scribed black
plate to afford a new guide image for the red lines, etc.
To gain maximum advantage of the contact processes in the photo
graphic dark room a punch- and stud system is chosen to secure
accurate register of all separate map components during the
exposure.
In the beginning a hand punch was used but the results, though
rather good, were not quite satisfactory.
In 1962 we devised and constructed a punching machine on which
Geodetic Engineers of the Topographic Service of the Netherlands, Delft:
