Quality assessment of X- and C-SRTM with ERS-tandem DEMs over 4 European CEOS WGCV test sites.
Jan-Peter Muller(1) and Dietmar Backes(1)
University College London,
London WC1E 6BT,
The CEOS working Group on Calibration/Validation (WGCV) Sub-group on
"Terrain mapping from satellites" (of which the first author is Chair) recently
selected 4 test sites in Europe for a comparative assessment of different DEM
Results will be presented on the quality assessment of X- and C-SRTM for
these sites in the UK (North Wales), Spain (Barcelona), France (Aix-en-
Provence) and Germany (Bavaria). Independent DTMs obtained from national
mapping sources or via the SPOT-5 HRS assessment campaign are used for
validation and LANDSAT-5 or -7 data used for the interpretation of height
differences. For the UK, ERS-tandem DEMs from the LANDMAP project (Muller
et al., 1999) are also assessed and kinematic GPS data collected as part of
LANDMAP employed for assessing all 3 DEMs.
Results indicate that for all 4 test sites, both X- and C-SRTM DEMs are not co-
registered with the available "ground truth" DEMs and not co-registered with
each other. For one site, a simple translation was required (UK) whilst the other
3 sites required that a rubber-sheet warping using a 1st order affine
transformation was required. Most height differences remaining are due to forest
cover with a small effect in very rugged areas due to SAR look angle in steep
sided valleys. The SRTM DEMs in the UK have an overall mean difference of
around 1m and a standard deviation in the range 4-6m. The SRTM results are
poorer for the other 3 European continental sites and an analysis of the reasons
for this are discussed. For LANDMAP in rugged areas the standard deviation is
affected by atmospheric effects resulting in values around 20m whilst in flat
regions the standard deviation is around 1-3m.
Preliminary results will be shown on the detection of outliers in these DEMs
using novel statistical methods for outlier detection and an early indication
shown on how these could be used to plug gaps and replace outliers in the
fusion of different DEM sources.
X-SRTM DEM data were kindly provided by DLR under Principal Investigator
121. C-SRTM DEM data was kindly provided by JPL. DTMs of Barcelona and
Bavaria were kindly provided by Dr. Wolfgang Kornus (ICC) and Prof. Dr. Ing.
Manfred Schroeder (DLR-IMF) respectively as part of the SPOT-HRS study.
Muller, J.-P., J.G. Morley, A. Walker, J. Barnes, P.A. Cross, I.J. Dowman, K.
Mitchell, A. Smith, K. Chugani, and K. Kitmitto, The LANDMAP project for the
creation of multi-sensor geocoded and topographic map products for the British
Isles based on ERS-tandem interferometry., in Proc. Second International
Workshop on ERS SAR Interferometry on "'Advancing ERS SAR Interferometry
from Applications towards Operations'", pp. 9pp, ESA, 10 – 12 November 1999,
Palais des Congrès, Liège, Belgium, 1999
Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,