TITLE:
Study of Some Lakes in the North-Eastern Romanian Plain Using the Coherence Image of the Tandem Pair (ERS-1 and ERS-2)
AUTHORS:
Kamel Hachemi, Marta Jurchescu, Florina Grecu, André Ozer, Mircea Cristian Visan
KEYWORDS:
Coherence; Buzau; Lakes; Radar; SAR; Tandem Pair; ERS-1; ERS-2
JOURNAL NAME:
Advances in Remote Sensing,
Vol.3 No.1,
March
4,
2014
ABSTRACT:
In radar SAR interferometry (InSAR/DinSAR), a Tandem
pair (ERS-1/2) is used for the realization of a DEM or the detection of
deformations of a major event (e.g. earthquake) occurring between two
acquisitions. The advantage of the Tandem pair is the time interval of 24 hours
between the two captures. Generally, there is no temporal decorrelation
considering the small difference in time between the acquisitions, which
results in a good coherence. The coherence image is used indirectly in radar
SAR interferometry as an indicator of the levels of confidence of the interferograms.
It can be used in a direct way to identify and delimit the various movement
zones which disturb the phase of the radar wave. The objective of this work is
to show the utility and the effectiveness of the coherence image in the
cartography of lakes and vegetation in a region at the Curvature of the
Romanian Carpathians1. Between the two
acquisitions dates of May 28 and 29, 1995, there was no geological process
involving displacements in direction of the radar. This pair represents the
only one among the other pairs which gave a good coherence for the whole scene.
In the flat part, one notes a good coherence except for the lakes. They are well
represented by very dark colours with zero coherence. In the part of high
altitude, especially where there is vegetation, a bad coherence can be clearly
seen. Using this image (coherence), one could distinguish the parts with
vegetation in great movements due to the effects of the wind, therefore
characterised by great heights. The coherence image thus makes it possible to
delimit two natural elements in this area, the lakes and the vegetation. The
lakes are well delimited, in particular when they are full as in the rain
seasons. To show this utility and this effectiveness of the coherence image, we
measured the surfaces and dimensions of the lakes based on the Tandem pair and
to make a comparison with the existing data and to interpret the results
obtained. The three lakes, located in the plain to the East and North-East of
the Buza;u town, clearly appear in the coherence image.