A new information source: very high resolution

For a long time, it was only the military that had access to very high resolution satellite images. Recently, however, access has become much wider and many civilian or even commercial applications have been developed. Today a number of satellites offer images of this kind, with an increasingly precise resolution close to 50 centimetres. These images provide a useful complement to aerial photography as they permit the repeated observation of a quite large area over a number of spectral bands. The limits of high resolution instruments such as LANDSAT TM and SPOT HRV have become apparent in many applications, particularly in urban areas. On the other hand, very high resolution image proved to be particularly useful especially in support of decision-making at local or regional level. A new fi eld has opened up to show how and to what extent data supplied by very high resolution sensors can meet the growing demand for geotopographic information and thereby contribute to the improved management of urban and semi-urban areas.

The SPIDER project was able to benefi t from the combined efforts of fi ve research teams who pooled their knowledge and know-how. In addition to their expertise in processing and interpreting satellite data, some of these teams had specifi c experience of town planning and urban management. Enjoying close contacts with the local and regional authorities in the regions studied, they were well placed to identify real information needs. This enabled the development of operational applications to concentrate on precise subjects. Examples include the improvement of information extraction from very high resolution images in an urban environment, the detection of signifi cant urban changes, the generation of 3D data that include non-natural elements, the mapping of urban land cover and the combined use of high and very high resolution images for the detailed mapping of impervious surfaces that play such a crucial role in problems of repeated flooding.

• To identify useful applications for decision-makers at local and regional level.
• To define optimal methods for improving spatial information extraction from high and very high resolution (HR and VHR) data, with the aid of innovative image processing techniques and with the emphasis on urban areas.
• To develop value-added products that support these applications and that can be consulted by means of everyday interfaces, such as CD-Rom or the Internet.