DEM OPTIMIZATION USING SATELLITE IMAGES 
Massoud Sharif 
International Institute for Aerospace Survey and Earth Sciences (ITC) 
P.O. Box 6, 7500 AA Enschede, The Netherlands 
Tel. +31-53-4874345, Fax. +31-53-4874335 
E-mail: SHARIF Q ITC.NL 
Mehrdad Jafari Salim 
National Cartographic Centre of Iran 
Commission IV, Working Group 4 
KEYWORDS: Image map, DEM, SPOT image, geometric correction radiometric correction, matching concept, correlation, 
epipolar line, orthimage. 
ABSTRACT 
An important use of satellite data is the production of image maps. Today, production of digital ortho images has become 
more operational due to the development of more powerful computers with sufficient resources, easier acquisition of input 
data, increased generation of digital data, development of many commercial ortho image production systems, and new 
application areas, particularly in connection with GIS and digital mapping. 
The purpose of the research work was to analyze the capability and possibility of applying the automatic DTM generation 
methods from stereopairs of SPOT imagery intended for 1:50 000 scale image maps. The experiment was an automatic 
DEM generation, performed on a stereopair of SPOT imagery (panchromatic, level 1A) covering a hilly area geographically 
located in the Aix-en-Provence region in the south of France. SPOT panchromatic stereopair (level 1A) supplemented with 
morphologic lies provide the primary information. The processing is applied to an image dataset of 2000010000 elements 
200 km? on the ground. The 10*10 m grid automatic DEM is generated, and used to correct the image data. The 20 m 
interval manual height measurement on TRASTER T10 along three different lines within the area is accomplished to obtain 
three different profiles, to evaluate the systematic error on automatic generated DEM. The 10 m interval contour lines of the 
1:25,000 scale topoplot produced a Digital Elevation Model, which is used to evaluate the relative accuracy of automatic 
generated DEM. 
INTRODUCTION 1. EXTRACTION OF INFORMATION FROM 
SATELLITE DATA 
The increasing demand of the map for planning and 
development on one hand, and limited application of ^ A variety of different production processes for extracting 
obsolete maps because of continuous changes of the thematic information about the Earth's surface from satellite 
topography of the Earth, on the other hand are putting data are present. Two general methods, namely visual 
pressure for faster and more economical map making. As image interpretation and computer-assisted image analysis, 
the analogue techniques for topographic mapping and map that can support topographic mapping are outlined. These 
updating are time consuming, labour intensive and methods can be applied at different levels. Regardless of 
expensive, the photogrammetric and cartographic the level or combination of methods employed, there is 
communities are roused to explore faster and operational almost always a requirements for effective man-machine 
techniques for topographic mapping. interaction. Furthermore, the quantity and quality of 
Remote sensing data from space seem to bring a potential thematic information that can be extracted from satellite 
solution for this problem, specially with the significant data increases when combinations of various types of 
improvement in spatial and resolution of spaceborne satellite data are used and when the satellite data are 
imagery. combined with other types of graphic and tabular data 
However, a more important and successful use of satellite [Nyquist, 1987; Lauer, 1986]. 
data is the production of image maps. Image maps based 
on digital ortho images provide great advantages in 2. COMBINATION OF SATELLITE INFORMATION 
comparison to their analogue counterparts, especially with WITH CONVENTIONAL SOURCES 
respect to the flexibility, production of derived products and 
combination with other datasets. Satellite-derived data rarely provide all information sought 
and, in any case, in order to be useable, they need to be 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996 
  
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