Analysis of Recent Global Geopotential Models Over the Croatian Territory
Independent quality control of the national geoid model HRG2000 was performed using 65 control points, obtained through the realization of EUVN and EUVN_DA projects and the Croatian fundamental gravity network. Ellipsoidal heights and positions of the con
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Analysis of Recent Global Geopotential Models Over the Croatian Territory M. Liker, M. Luˇci´c, B. Bariši´c, M. Repani´c, I. Grgi´c, and T. Baši´c
Abstract Independent quality control of the national geoid model HRG2000 was performed using 65 control points, obtained through the realization of EUVN and EUVN_DA projects and the Croatian fundamental gravity network. Ellipsoidal heights and positions of the control points are precisely determined by GNSS measurements while the geodetic heights are obtained by geometric levelling. The latest geoid model HRG2000 is related to the old vertical system. The analysis indicated the need for a new improved national geoid model which has to be connected to the new vertical system HVRS71. As preparation, and as first step, an analysis of the global geopotential models was made, using eleven recent CHAMP and/or GRACE global models. The statistics of the differences between GNSS/levelling height anomalies (ζHVRS71 ) and corresponding anomalies obtained from global geopotential models (ζMODEL ) shows that EGM2008 model is most suitable at this moment. Another interesting fact is that all global models are approximately 93 cm above the new Croatian vertical datum.
HRG2000, is related to the old vertical system. This analysis is the preparation for the modelling of the national geoid model that will be connected to the new vertical system. The differences of height anomalies calculated from control GNSS/levelling points and those from global geopotential models are the indicator of which global geopotential model is the best for describing Earth’s gravity field on our territory. Global geopotential models are usually used for the definition of long wavelength gravity field structures in geoid modelling. The differences between height anomalies that were attained from three sources were used in the analysis. – Height anomalies, calculated from GNSS/levelling data available at EUVN, EUVN_DA and FGN (Fundamental Gravimetric Network) points (hGNSS HHVRS71 = ζHVRS71 ). – Height anomalies, interpolated from the HRG2000 national geoid model (ζHRG2000 ), and the – Height anomalies obtained from eleven global geopotential models (ζMODEL ).
36.2 Used Data 36.1 Introduction In the Republic of Croatia there are two vertical systems currently in use. The older one is known as TRIESTE, and the more recent one is known as HVRS71. By 2010 Croatia should change the old vertical system to the new one. The national geoid model, M. Liker () Croatian Geodetic Institute, Zagreb 10144, Croatia e-mail: [email protected]
Altogether 65 EUVN, EUVN_DA and FGN control points were used in the analysis. EUVN (EUropean Vertical Network) project in Croatia was realized in 1997. Eight EUVN points were defined; see Marjanovi´c and Raši´c (1998). The first analysis of geoid heights indicated two problematic points (HR05 Split and HR01 Bakar), see Kenyeres et al. (2002). The problems were solved through EUVN Densification Action (EUVN_DA) project in 2005,
S.P. Mertikas (ed.), Gravity, Geoid and Earth Observati
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