FO TOGRAMMETRIE
Ir. P. A. ROOS,
Signalisation Experiment "Gendringen"
In the application of photogrammetry for large scale plotting
often use is made of signalised points; they are among others, used
as pass points. The reasons for signalisation will further not be
discussed here. The purpose of the experiment which will be
described here, was to obtain more knowledge about the influence
of the colour of the signal on the visibility of the image in the
aerial photograph.
To achieve this 25 different types of signals were laid out in the
terrain, in this case a field of about 300 x 300 m near Gendringen,
in the eastern part of the Netherlands. Of each type, 10 signals were
laid out on (a) the barren arable land and 10 on (b) meadow-land.
The ten signals of one type were not placed together, but the
whole group of 250 signals was scattered arbitrarily over the area.
The field-work was done by the Re-allotment-office in Arnhem,
the further working-out by the Photogrammetric Service of the
Cadastre.
A view of the different types of signals is given in table 1.
Investigated were the colours white, yellow, white with glass
particles, yellow with glass particles and grey (this last colour was
the unpainted base-material) and the dimensions 30 X 30, 20 x 20,
15 X 15, 10 x 10 and 7x7 cm. In the table the signals are in
dicated with a number. In the following, for the sake of con
venience, these numbers will be used to identify the signal types.
The test-area was photographed by K.L.M.-Aerocarto with the
Zeiss camera 2 x RMK 21/18 on the scales 1:2000, 1:4000,
Photogrammetric Service of the Cadastre, The Hague:
TABLE i
Signal types
Colours
Dimensions
White
Yellow
White
with
glass part.
Yellow
with
glass part.
Grey
30 x 30 cm
1
2
3
4
5
20 x 20 cm
6
7
8
9
10
15 X 15 cm
11
12
13
14
15
10 x 10 cm
16
17
18
19
20
7 x 7 cm
21
22
23
24
25
