Sizing and deployment of wireless telephone networks demand various kinds of information. Network planners mostly use satellite image maps, which depict land use and land cover features in urban areas (clutter maps), and digital terrain models (DTMs) or digital elevation models (DEMs) overlaid with communications infrastructures. In recent years, Earth observation data have started catering for these requirements. Thanks to their stereoviewing capacity and their ability to acquire coverages of most of the world’s cities in a single image, the SPOT satellites have built up a large archive of urban imagery that is used to develop standardized products. These products offer a resolution of 10 or 20 metres, making it possible to distinguish more than 10 urban land-use classes.

A Clearer Picture of Urban Areas
What mobile phone network planners most need today is a more detailed picture of land use, particularly in dense urban areas. To meet this demand, SPOT 5 will offer products with improved resolution and information content closely tailored to the requirements of operators and equipment manufacturers.

Determining building heights
By digitizing building outlines on two SPOT 5 2.5-metre black-and-white scenes acquired from different viewing angles, and by analyzing the differences between the two, we can determine the height of objects on the ground using photogrammetry techniques. This information, combined with a DTM showing terrain elevation above sea level, reveals extra detail for determining building heights. Such products offer a z-accuracy of around 2.5 metres.

Enhancing land-use information
To obtain better land-use information for telecommunications network planning, we have to define building height and building density classes and extract mean height and density values for each class. A possible method of achieving this would be to add an extra step to the standard process for producing satellite image maps, DEMs and land-use maps. This step would use automatic or semi-automatic classification of the DEM containing the elevation of each point to classify groups of buildings according to their height and density, and thus obtain a more detailed nomenclature.

References
• SPOT 5 Preparatory Program: using SPOT 5 VHR data to generate geographic databases for mobile phone network planning − Istar
• SPOT 5 Preparatory Program: Using SPOT 5 imagery to develop databases for telecommunications frequency planning − SPOT 5 International Conference, 14-15 June 2001 − Geoimage