The Huddinge test area 
In order to investigate the differences possibly appearing when plotting 
from aerial photographs taken from altitudes of 600 and 450 metres res- 
pectively (scales of the negative 1:4000 and 1:3000), and with 
panchromatic and colour film respectively, a test area was arranged 
within an arbitrarily chosen map sheet within the district to be mapped. 
The test area was measured by geodetic measuring as regards position as 
well as height, during which a great number of points were measured as 
to height (about 800 points per hectare). 
This area was photographed four times from different altitudes and 
using various film material. Then the results were worked out in four 
different instruments at four different offices. Table 2 below gives the 
arrangement of the test. 
  
  
Table 2. 
Test 1 2 3 
Flying altitude .... 600 metres 600 metres 450 metres 450 mecs À 
Base of emulion . Polyester | Acetat | Polyester Acetat 
Edition E a  Panchromatie E Colour Panchromatic Colour 
Dupwiwe ..... «1 Che 4 Fim Glass Film 
Instrument NDA. . Wild A7 à Wild A7 i Wild A8 Wild A8 
Number of m E 
models... ...... : 1 1 2 2 
Office teens … il Göteborg j Stockholm Falun : Malmö 
Stereo processing 
The stereo operators were instructed to carry out an ordinary plotting 
in the scale 1: 400 with contour lines of 0.5 metres. In connection with 
the plotting, a series of measures was adopted in view of the analysis to 
follow. 
In the planimetric compilation about 120 details of various kinds, such 
as the corners of houses, poles, wells, kerbstones, and fences, were deter- 
mined by coordinates. Eight signalled points, known by coordinates, were 
also measured. When contouring, the operators drew every other contour 
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