Baseline combination for InSAR DEM atimetric resolution enhancement
Dominique Derauw(1) and Anne Orban(1)
Centre Spatial de Liege,
Avenue du Pre Aily,
Combination of several interferograms of a same area, each having its own ambiguity of
altitude, allows producing a combined interferogram with either a better signal to noise
ratio or a lower ambiguity of altitude, unreachable from a single interferometric pair.
Baseline combination by averaging can only be applied on unwrapped phases.
Therefore, each interferogram must be unwrapped prior to combination. We thus
implemented a three step phase unwrapping procedure allowing to take fully advantage
of an interferometric data set containing several InSAR pairs of a given site. In the first
step, the best interferogram of the set is unwrapped classically to generate a first phase
approximation. The second step consists in flattening all the other interferograms and
to unwrap a filtered version of them. The third step consists in adding both components
with the residual phase issued from the difference between the flattened interferogram
and the filtered version of itself.
Phase averaging allows to lower substantially the phase standard deviation and thus to
increase the altitude accuracy.
InSAR baseline combination by summation allows reaching peculiar equivalent baselines
while raising signal to noise ratio in the resulting interferogram. Despite this drawback
such combination revealed to be highly useful in atmospheric artifacts identification and
localization. Choosing adequately the interferograms to combine allow to generate
interferograms with very short baseline in which the topographic phase component can
be neglected, revealing artifacts before going further in a then useless processing.
Baseline combination process was developed in the frame of a DUP project. An example
of baseline combination usefulness is given using five Tandem pairs of the area of
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,