SAR repeat-pass coherence in winter for boreal forest applications. A first comparison of ASAR and JERS-1 SAR.
Leif E. B. Eriksson(1) and Christiane Schmullius(1)
Interferometric coherence from the ERS-1/2 tandem mission has in
several studies proved to be a useful tool for forest monitoring. After
the loss of ERS-1, the focus of InSAR studies has to some extent moved
to repeat-pass solutions for current and near term satellite sensors
like Envisat ASAR and ALOS PALSAR. Recently published results show that
44-day repeat-pass coherence from the SAR on JERS-1 can give
information about forests if the acquisitions are made during stable
winter conditions, e.g. in Siberia. This paper will present the first
comparison between repeat-pass coherence from ASAR and JERS-1 SAR.
SAR data from Envisat and JERS-1 have been acquired for one of the
SIBERIA-II project test sites in the northern taiga in central Siberia.
The acquisitions are from the winter season, which give the most
favourable conditions for coherence estimation over 35 and 44 days
respectively. The coherence estimation was done with an adaptive window
size taking into account phase slope, texture of the averaged
backscattering coefficient and the local coherence level. Initially
Landsat ETM quicklook images from June 2002 have been used to give
independent information about the forest coverage. In addition, forest
inventory data will allow an assessment of the differences between C-
band and L-band coherence for stem volume estimation.
The processed repeat-pass coherence shows relatively high values both
for ASAR and JERS-1 SAR. Statistics for the coherence levels for the
available land cover types will be presented. In the ASAR coherence
image, which is from a more recent date than the JERS-1 coherence, a
new fire scar can be identified. The study confirms that when the
requirements of stability are met, coherence from repeat pass
acquisitions gives exploitable coherence levels. The goal for the
coming winter is to extend this study to more test sites in Siberia,
but also in northern Europe.
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,