The usefulness of VHR images for public administrations in an urban hilly region

This paper presents some results of the SPIDER project currently achieved in and
around the city of Liège located in a hilly landscape. A Quick Bird image bundle product acquired
on the 26th September 2003 is used. Digital spatial data like Very High Resolution (VHR) satellite
images could be provided to the public authorities of the Walloon region thanks to the Walloon
cartographic gateway. In urban context and especially in hilly region, such images must be orthorectified
using a Digital Surface Model (DSM). A 1 m resolution DSM was elaborated by exploiting all the
3D data available in the study area. Firstly, a TIN was generated from vector data (points, lines and
polygons) selected, on the one hand, from the 1:50 000 (DTED-WGS) and the 1:10 000 (DTM-
10000, Top10v-GIS) cartographic database provided by the Belgian NGI and, on the other hand,
from the 1:1 000 3D topographic database of the Walloon region (PICC). Then the TIN was
rasterised and the DSM airborne LIDAR acquired along the main river-valleys is superimposed on
the result. The ortho-image was then produced. The public authorities consider it as an end-product
by itself which could be used in the place of the obsolete aerial orthophotos in the fast changing
urban areas. Normally, the ortho-image of Liège should be available on the map server of the
Walloon region in 2005, in order to check its usefulness for local and regional authorities. Moreover
the local planning agency wish to take the opportunity of this study to update the spatial databases
covering industrial and business development areas delineated on the urban plan.