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EPOS-GNSS double-difference processing - Prototype
EPOS-IP project
Scientific objectives
The EPOS-IP project (European Plate Observing System, Implementation Phase) is an infrastructural research project that delivers projects and services to the Earth Sciences community. The "GNSS data and products" group brings together a dozen European partners. Its goal is to record and distribute GNSS data from permanent stations throughout Europe (Rinex files) and related products (daily solutions, position time series, velocity and deformation fields). OSUG/ISTerre hosts one of the two GNSS data processing centers.
Description
This interactive map brings together approximately 1500 stations scattered throughout Europe and includes all data over an 18-year period (2000-2017). The database is composed of:
– EPN stations
– A complete dataset for France (RENAG, RGP, ORPHEON),
– Italian stations within the RING network
– Greek stations within the NOA and SMARTNET networks
Interactive map with time series data sets
Maps of horizontal and vertical velocities and velocity field text files
Horizontal velocities compared to the Eurasian plate. This velocity field is composed of the 1092 stations, which fulfill the quality criteria defined in the text below. The A, B and C categories defining the velocity robustness are respectively in green, orange and red. The black polygons represent the areas considered as tectonically active zones.
Maps of vertical velocities
The A, B and C categories defining the velocity robustness are represented as circles, squares and triangles, respectively.
The massive processing implementation requires innovative strategies in order to satisfy the efficiency, robustness and automation criteria for the computation of another usual GNSS product: the velocity field.
After a technical validation, MIDAS software appeared to be the most appropriate tool. This software includes an automatic estimator of time-series trend (Blewitt at al., 2016). By using a statistical method based on a set of position pairs separated by one year, it produces GNSS velocities with very low sensitivity to outliers, steps and seasonality.
Three robustness categories on MIDAS velocities have been defined. The robustness quantification is done through two MIDAS breakdown points:
– the maximum number of large outliers that can be tolerated.
– the threshold of large steps as a function of the time span to maintain a reliable velocity estimate.
(To know more about MIDAS and the two MIDAS breakdown points, see Blewitt et al., 2016).
We eliminate from our analysis the stations for which the breakdown criteria were not satisfied. In addition, we eliminate the stations for which the error estimated by MIDAS is superior to a certain value which changes following the three robustness categories (see following table).
MIDAS error threshold for the three robustness categories
Solutions files
Solutions (position time series and velocity field) are available through the product DOI page.
European partners
UBI (Portugal), ROB (Belgium), NOA (Greece), GOP (Czech Republic), CNRS (France), INGV (Italy), IMO (Iceland), LTK (Hungary), KOERI (Turkey), INCDPM RA (Romania), LM (Sweden), BAS (Bulgaria), BKG (Germany)
ISTerre-OSUG team
Anne SOCQUET, OSUG physicist
Andrea WALPERSDORF, OSUG physicist
Gaël JANEX, Research engineer
Former members
Nathalie COTTE, Research engineer
Alizia TARAYOUN, Research engineer
Aline Déprez, Research engineer
Mary Grace Bato, OSUG monitor
Contact
Anne SOCQUET
Funding
EPOS-IP European project