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: • • • • 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: • • • 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: • • • 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.