Soutenance Séries temporelles de la subsidence de la ville de Mexico obtenues par florence . tupin
From: florence.tupin AT telecom-paristech.fr
Cc:
Subject: Soutenance Séries temporelles de la subsidence de la ville de Mexico obtenues par
Date: Wed, 12 Nov 2008 11:23:07 +0100 (CET)
interférométrie radar
Date: Wed, 12 Nov 2008 11:23:07 +0100
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From: florence.tupin@telecom-paristech.fr
Lopez-Quiroz P=E9n=E9lope
sountient sa these
S=E9ries temporelles de la subsidence de la ville de Mexico obtenues par
interf=E9rom=E9trie radar.
le 14/11/2008
a TELECOM ParisTech.
Directeur: Florence Tupin
Marie-Pierre Doin
Pierre Briole
Directeur: florence.tupin@telecom-paristech.fr
Jury: -Mme. B=E9n=E9dicte Fruneau, Ma=EEtre de Conf=E9rences, Universit=E9 =
de Marne-la-Vall=E9e
(Rapporteur)
- M. Claudio Prati, Professeur, Politecnico di Milano (Rapporteur)
- M. Nicolas Florsch, Professeur, Universit=E9 Pierre et Marie Curie
(Examinateur)
- M. Jean Marie Nicolas, Professeur, Telecom ParisTech (Examinateur)
- M. Francesco Sarti, Charg=E9 de Recherche, Agence Spatiale Europ=E9ene
(Invit=E9)
- Mme. Florence Tupin, Ma=EEtre de Conf=E9rences (HDR), Telecom ParisTech
(Directrice de th=E8se)
- Mme. Marie Pierre Doin, Charg=E9e de Recherche, Ecole Normale Sup=E9rieure
(Co- Directrice de th=E8se)
- M. Pierre Briole, Charge de Recherche CNRS, Ecole Normale Sup=E9rieure
(Co- Directeur de th=E8se)
Labo: TELECOM ParisTech, Paris
Mot-clef: SAR imagery, differential interferometry, SBAS methods
Resume: In Mexico city, subsidence rates reach up to 40 cm/yr mainly due to=
soil
compaction led by the
over exploitation of the Mexico Basin aquifer. In this work we map the
spatial and temporal patterns of the Mexico city subsidence by
differential radar interferometry, using 38 ENVISAT images acquired
between end of 2002 and beginning of 2007. We present the severe
interferogram unwrapping problems partly due to the coherence loss but
mostly due to the high fringe rates. This difficulties are overcome by
designing a new methodology that help the unwrapping step. Our approach is
based on the fact that the deformation shape is stable for similar time
intervals during the studied period. As a result, a stack of the five best
interferograms can be used to compute an average deformation rate for a
fixed time interval. Before unwrapping, the number of fringes is then
decreased in wrapped interferograms using a scaled version of the stack
together with the estimation of the atmospheric phase contribution related
with the troposphere vertical stratification.The residual phase,
containing less fringes, is more easily unwrapped than the original
interferogram. The unwrapping procedure is applied in three iterative
steps. The 71 small baseline unwrapped interferograms are inverted to
obtain increments of radar propagation delays between the 38 acquisition
dates. Based on the redundancy of the interferometric data base, we
quantify the unwrapping errors and show that they are strongly decreased
by iterations in the unwrapping process. A map of the RMS interferometric
system misclosure allows to define the unwrapping reliability for each
pixel. Moreover, we present a new algorithm for time series analysis that
differs from classical SVD decomposition and is best suited to the present
data base. Accurate deformation time series are then derived over the
metropolitan area of the city with a spatial resolution of 20 x 20 m.
Finally, the nonlinear components of the deformation are modelised and
analysed.
Keyword: SAR imagery, differential interferometry, SBAS methods
Abstract: In Mexico city, subsidence rates reach up to 40 cm/yr mainly due =
to soil
compaction led by the
over exploitation of the Mexico Basin aquifer. In this work we map the
spatial and temporal patterns of the Mexico city subsidence by
differential radar interferometry, using 38 ENVISAT images acquired
between end of 2002 and beginning of 2007. We present the severe
interferogram unwrapping problems partly due to the coherence loss but
mostly due to the high fringe rates. This difficulties are overcome by
designing a new methodology that help the unwrapping step. Our approach is
based on the fact that the deformation shape is stable for similar time
intervals during the studied period. As a result, a stack of the five best
interferograms can be used to compute an average deformation rate for a
fixed time interval. Before unwrapping, the number of fringes is then
decreased in wrapped interferograms using a scaled version of the stack
together with the estimation of the atmospheric phase contribution related
with the troposphere vertical stratification.The residual phase,
containing less fringes, is more easily unwrapped than the original
interferogram. The unwrapping procedure is applied in three iterative
steps. The 71 small baseline unwrapped interferograms are inverted to
obtain increments of radar propagation delays between the 38 acquisition
dates. Based on the redundancy of the interferometric data base, we
quantify the unwrapping errors and show that they are strongly decreased
by iterations in the unwrapping process. A map of the RMS interferometric
system misclosure allows to define the unwrapping reliability for each
pixel. Moreover, we present a new algorithm for time series analysis that
differs from classical SVD decomposition and is best suited to the present
data base. Accurate deformation time series are then derived over the
metropolitan area of the city with a spatial resolution of 20 x 20 m.
Finally, the nonlinear components of the deformation are modelised and
analysed.
