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Regional Models

Greek Seas (NTUAMGv1)

  Authors: I. Mintourakis, et al.     Created: 2019    Resp: I. Mintourakis  
      Status: PUBLIC    

NTUAMGv1 is a marine geoid model of the Greek Seas, computed at the Higher Geodesy Laboratory, School of Rural and Survey Engineering, National Technical University of Athens. The acronym NTUAMGv1 stands for National Technical University of Athens Marine Geoid, Version 1. The marine geoid covers the area 33 ° < lat < 42° and 19° < lon < 30°, with a grid spacing of 30". The reference ellipsoid is GRS80 in the ITRF2005 reference frame. The model implements the so-called "oceanographic" approach for the realization of the marine geoid, as it uses only satellite altimetry Sea Surface Height (SSH) observations and oceanographic data. Thus, the marine geoid is the result of the Mean Sea Surface (MSS) minus the Mean Dynamic Ocean Topography (MDT) as computed by ocean circulation models. For the NTUAMGv1 model computation the National Technical University of Athens MSS, Version 1, was used, as well as the Synthetic MDT RIO07. The EGM2008 global gravity model was also used to fill MSS gaps over land (mainland and islands) and to describe the long wavelengths of the model through a sort of Remove-Compute-Restore procedure. In particular, EGM2008 values were first subtracted from the adjusted SSH observations and then added back to the interpolated grid residuals to obtain the final geoid model. In the open ocean the agreement of NTUAMGv1 to EGM2008 (agreement refers to the standard deviation of the differences between the two models) is at the level of 6 cm, while close to the coast their agreement is at the level of 10 cm. The original file format of the NTUAMGv1 model is the Binary Generic Mapping Tools grid (netcdf) using node registration.

I. Mintourakis (2014). Adjusting altimetric sea surface height observations in coastal regions. Case study in the Greek Seas. Journal of Geodetic Science, 4, pp. 109-122. DOI: 10.2478/jogs-2014-0012
I. Mintourakis, G. Panou, D. Paradissis (2019). Evaluation of ocean circulation models in the computation of the mean dynamic topography for geodetic applications. Case study in the Greek seas. Journal of Geodetic Science, 9, pp. 154-173. DOI: 10.1515/jogs-2019-0015