Analysis of buildings height computed on a DSM generated from a VHR satellite stereopair

At the final meeting of the SPIDER project, the users wanted to know if it was possible to evaluate
the building height or the number of floors, from the DSM obtained from a VHR satellite stereopair.
Combined with the 2D delineation of the buildings – for example coming from the cadastre register
- this information could be useful in urban studies – e.g. population density assessment - or to
generate quasi realistic 3D views.
In this example, the DSM is extracted from an IKONOS stereopair (DSMsat) on the hilly area of
Liège in Belgium. It is used in combination with a 3D vector file. On the one hand, this file is used
for the 2D delineation of the buildings. On the other hand, the third dimension provided by this file
is also exploited for the assessment of the extracted building height. Moreover LIDAR data are
also available over the test area, permitting the creation of a reference DSM (DSMref).
* The first step of the process consists in the determination of the ground altitude around the
buildings. A procedure was setup in order to compute it and to generate the DTM for the reference
and satellite data (DTMref and DTMsat).
* The second step consists in the extraction of statistics, for every building (min, max, mean, etc.)
as well from the DSMsat and DSMref, as from the DTMsat and DTMref.
The analysis shows that the satellite approach globally underestimates the building height of about
4 m. These results are discussed regarding building height versus the area and the heterogeneity
of the roof height.