Generation of DEM with sub-metric vertical accuracy from 30' ERS-ENVISAT pairs
Claudio Prati(1) and Fabio Rocca(1)
Piazza L. da Vinci 32,
According to the spectral shift principle , distributed scatterers
can be coherently observed by ERS and ENVISAT SAR systems despite of
their carrier frequencies 30 MHz frequency shift. A 2km normal baseline
should be set in order to compensate such a carrier frequency
difference for almost horizontal terrain. This type of SAR
interferometry configuration can be usefully exploited to get DEMs of
rolling topographic features with very high vertical accuracy. A first
experimental evidence has already been provided , . The goal of
this presentation is twofold: first an ERS-ENVISAT interferometric DEM
of a rural area along the rivers Réveillon and Yerres (tributaries of
Seine) in the immediate neighbourhood of Paris will be shown and
analyzed, then the main advantages and limitations of such a system
will be discussed.
This experiment has been carried out using an ERS-ENVISAT
interferometric pair with a normal baseline of about 1.5km (the 30MHz
frequency shift is partially compensated on cross-track terrain slopes
ranging from 0 to 7 degrees) and a very short (30 minutes) temporal
separation, thus containing the temporal decorrelation to acceptable
The resulting interferogram seems very attractive in order to
reconstruct high vertical precision topographic profiles (20-40 cm)
suitable for characterising flood plains.
Even though the Doppler Centroid (DC) variability of ERS-2 in Zero Gyro
Mode sets an additional constraint, a suitable azimuth common band
filtering allows one to exploit successfully ERS-ENVISAT
interferograms, as long as the DC difference is not too high (a
reasonable limit could be about 1000 Hz). In our data the DC
difference was found to be about 800Hz thus leaving a common band in
azimuth greater than 20% of the ERS Pulse Repetition Frequency.
[1.] F. Gatelli, A. M. Guarnieri, F. Parizzi, P. Pasquali, C. Prati, F.
Rocca. "The Wavenumber Shift in SAR Interferometry". IEEE Transaction
on Geoscience and Remote Sensing, Vol. 32 No. 4, July 1994.
[2.] N. Adam, "Das erste Cross-Interferogramm aus Aufnahmen der
Radarsensoren ENVISAT/ASAR und ERS-2", available on-line at:
[3.] First Cross Interferogram using ENVISAT ASAR and ERS-2 SAR Radar
Data, available on-line at: http://envisat.esa.int/applications/la/.
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,