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SIMULATION OF PANCHROMATIC SPOT-DATA AT THE NATIONAL LAND 
SURVEY OF SWEDEN 
MATS WALLIN 
National Land Survey 
S-801 12 GAVLE SWEDEN 
ABSTRACT 
A simulation of Spot-data has been made by using orthophotos, 
digital terrain model and a scanner. In the simulation ortho photos have 
been put together and reduced to an image which has been digitized in a 
scanner. The scale and the aperture has been chosen so the size of the 
pixels correspond to 10 x 10 m on the ground. With the pixel size and the 
ortho photos the simulation will correspond to the future Spot-data in 
panchromatic mode. In a computer a calculation has been done line by line 
of the digitized image. In every line every pixel has been recalculated to 
a new position on the line, where Spot will register it, dependent on the 
distance from the track of the satellite, the earth curvature and the height 
in the terrain of the corresponding point on the ground. The simulated 
digital image has thereafter been plotted in the scanner. 
In this way three images have been produced, one with the track 
of the satellite over the centre of the ortho photo, one 274 km to the east 
and one 108 km to the west of the centre. From the central image a number 
of alternative products have been developed by copying the images with 
forestry maps at different scales. 
Introduction 
At the National Land Survey of Sweden Landsat-data has been investi- 
gated for a number of applications. In the investigations computer programmes 
and other forms of image processing of Landsat-data have been developed. In 
1984 the Spot-satellite is planned to be launched. Spot will have a greater 
resolution than Landsat and the capability to do off-nadir registration. The 
off-nadir registration will make it possible to do stereoscopic processing 
of satellite-images. 
To meet the new possibilities of Spot it is important that develop- 
ment of methods and computer programmes for processing of Spot-images is 
done as soon as possible to be well prepared for the launching. To get some 
material to work with the National Land Survey of Sweden at the commission 
of the Swedish Space Corporation has made a simulation of Spot-data, as 
digital and photographic images. The simulation corresponds to the registra- 
tion Spot, will do in panchromatic mode with a pixel size on the ground of 
10 x 10 mé: 
The area chosen for the simulation is 40 x 40 km2 in the middle of 
Sweden. The land use of the area is both farming and forestry. In some parts 
of the forest areas forestry maps are produced. Local differences in height 
in the area are up to 200 meters, enough to study stereoscopic effects in 
the simulated images. 
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