PhD Scholarship - Recherche

PhD Scholarship
Considering spatio-temporal correlations of GNSS station position time series
for a better determination of tectonic plate motions with respect to the
center of mass of the Earth
Supervisors:
Dr. Habil. ZuheirAltamimi (IGN - LAREG)
Dr. Paul Rebischung (IGN - LAREG)
Hosting institution: IGN - LAREG, Université Paris Diderot, 35 rue Hélène Brion, 75013 Paris, France
Application deadline: October 9th, 2014
Project description:
Nowadays, the determination of the current tectonic plate kinematics relies mainly on Global
Navigation Satellite System (GNSS) data. These data allow determining GNSS station displacements
with a precision of about 0.5 mm/year with respect to a reference frame with its origin at the center
of mass of the Earth. This reference frame is itself determined using GNSS data, as well as data from
other scientific global positioning systems, and is based on a precise estimation of the velocities of a
global network of geodetic stations. Any improvement in the station velocity estimation process
would therefore benefit to both the determination of the relative tectonic plate velocities, and to the
reference frame which allows expressing these velocities with respect to the center of mass of the
Earth.
A lot of permanent GNSS stations have progressively been deployed over the Earth for more than
twenty years, and many of them providepublicly available data. It is nowadays possible to determine
time series of daily GNSS station positions with a precision of a few millimeters. But significant errors
nevertheless exist, due for instance to instrumental changes, and need to be taken into account so as
to determine precise station velocities. GNSS station position time series also exhibit systematic
measurement errors which are correlated in space and time. The position time series of two nearby
stations thus show similarities, like the consecutive positions of some given station.
These statistical characteristics are nowadays only partially taken into account in the estimation of
GNSS station velocities, while a full consideration of these spatio-temporal correlations would allow
providing better velocity estimates for short time series as well as more realistic error estimates. This
spatio-temporal dependency is however very complex and non-stationary. Expressions or patterns
have been proposed in the literature, but turn out to be hardly exploitable in practice. The objective
of the project is therefore to propose an easily applicable velocity estimation method that would
take into account the available information about measurement errors, and could also incorporate
spatio-temporal dependency models for the residual errors and the geophysical Earth surface
displacements.
Proposed steps:
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Study of the spatial correlations of GNSS station position time series
Study of the estimation methods allowing the consideration of spatio-temporal error models
in large-scale problems (more than 10000 parameters)
Elaboration and implementation of a velocity estimation method
Study the contribution of this method to the determination of a reference frame, to the
observation of tectonic plate kinematics and to the observation of large-scale intra-plate
deformations
Collaborative framework:
This work will take place in the LAREG Reference System team (Zuheir Altamimi, Xavier Collilieux,
Laurent Métivier, Paul Rebischung). The research carried out in this project about the statistical
modeling of geodetic data will be connected to the LAREG activities in several domains:
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determination of the International Terrestrial Reference Frame,
multi-technique analysis of space geodetic observations,
homogeneisation of space geodetic time series.
Contact for informal enquiries: [email protected]
Eligibility:
Applicants must have obtained a Master 2 degree or higher in Mathematics, Physics or Earth
Sciences. (A Master 2 degree in Statistics or Geodesy would be appreciated.) A solid background in
statistics and computer programming is additionally required.
The three-year scholarship is expected to start between December 1st and December 15th, 2014 and
will benefit of a stipend of 1400 € per month during three years.
Application procedure:
Please send your application to [email protected] with copy to the supervisors: [email protected] and
[email protected]. The applications should clearly identify the title of the project and include
the following documents:
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CV (including any publications),
covering letter (outlining your academic interests, prior research experience and reasons for
wishing to undertake this project),
transcript (or interim transcript if you are still studying).
The closing date for applications is October 9th, 2014. Interviews are expected to take place in late
October. Decisions made by Admission Committee will be communicated by November 9th, 2014.