Improving spatial information extraction for local and regional authorities using Very-High-Resolution data - geometric aspects.

The purpose of the presented research project is to investigate how present-day EO-technology can support local and regional decision-making, particularly in Belgium, and to develop prototype versions of value-added products that fulfil some of the actual information needs, as expressed by Belgian authorities at the local and at the regional level. To accomplish this goal the proposal addresses both technical and user-oriented issues, and builds on the experience of five research teams, each with its own background and particular know-how.
The most important objectives of the project are:
- to define optimal methods for improved spatial information extraction from high- and very-high resolution data, based on innovative processing techniques;
- to identify useful EO-applications at the level of local and regional decision making that are made possible by applying the information extraction methods that will be developed; in this case especially 3D information
- to define and develop value-added core data products that will support these applications, and that can be consulted with easy-to-use, widely available IT-tools (CD-ROM, Internet, …).
One of the technical research modules is focussing on the geometrical aspects of VHR data processing. In terms of spatial resolution, VHR data have the required level of detail to resolve individual objects in the landscape, in a similar way as airborne data. As such, they have the potential of becoming a useful data source for the extraction of detailed, object-related information, and for the production of large-scale cartographic reference data. The geometry of VHR sensor data, however, completely differs from the geometry of aerial photographs (Bethel et al., 2001). Research is going on to evaluate the geometric qualities of present and future VHR standard data products, from the moment they become available, and to examine what level of geometric accuracy is attained with these data, depending on image parameters, processing strategies, and terrain characteristics (Zhou and Li, 2000).
The main objectives of the research module on geometric aspects of VHR data processing are:
a) to define an optimal procedure for the derivation of envelope DSMs (Digital Surface Models) and ortho-photoplans from VHR data;
b) to develop a theoretical model to study the effect of the oblique viewing angle of VHR data on image displacements caused by building height and relief;
c) to evaluate the geometric accuracy of satellite-derived envelope DSMs and ortho-corrected image data in comparison with similar products obtained by means of large-scale aerial photography.
The module about geometrical aspects is divided into six specific tasks.
a) GPS database creation
b) Creation of reference envelope DSMs based on aerial photography
c) Ortho-rectification of VHR images and aerial photography based on reference DSMs
d) Evaluation of the quality of VHR geo-referenced data
e) Modelling of displacements caused by terrain morphology and sensor viewing angle
f) Development of envelope DEMs from VHR stereoscopic imagery
The project is now in the stage where the quality of the georeferenced and orthorectified data is evaluated.