In the framework of the REAL GOCE project, a highresolution spherical harmonic representation of the Earth's topographicisostatic gravitational potential has been derived at the Geodetic Institute of the Karlsruhe Institute of Technology (KIT). The socalled RockWaterIce model (RWI model) is based on a threelayer decomposition of the topography with variable density
values and a modified AiryHeiskanen concept incorporating seismic Moho depths.
Overview:
 Release 2012: RWI_TOPO_2012, RWI_ISOS_2012, RWI_TOIS_2012
 Release 2015: RWI_TOPO_2015, REQ_TOPO_2015
Release 2012:
 RWI_TOPO_2012: Spherical harmonic representation of the Earth's topographic gravitational potential (N=1800)
 RWI_ISOS_2012: Spherical harmonic representation of the Earth's isostatic gravitational potential (N=1800)
 RWI_TOIS_2012: Spherical harmonic representation of the Earth's topographicisostatic gravitational potential (N=1800)
Vzz gravity gradient component of RWI_TOIS_2012 at the satellite altitude of GOCE
Main features:
 Threelayer decomposition of the topography using the 5′×5′ topographic database DTM2006.0 (Pavlis et al. 2007)
 Rigorous separate modeling of rock, water, and ice masses with layerspecific density values
 Rock: 2670 kg m^{3}, Water: 1000 kg m^{3}, Ice: 920 kg m^{3}
 Avoidance of geometry changes compared to classical condensation methods (e.g. rockequivalent heights)
 Ellipsoidal arrangement of the topography using the GRS80 ellipsoid as height reference surface
 Adapted and modified AiryHeiskanen isostatic concept
 Incorporation of seismic Moho depths derived from the CRUST2.0 model (Bassin et al. 2000)
 Locationdependent estimation of the crust–mantle density contrast
Further details are provided in Grombein et al. (2014).
Processing:
 Forward modelling in the space domain using tesseroid mass bodies (Grombein et al. 2013)
 Transformation of global gridded values to the frequency domain by applying harmonic analysis up to degree and order 1800
Model versions and download:
 Spherical harmonic coefficients of the RWI 2012 models are provided by three versions
(GM = 3.986004415e+14 m^{3} s^{2}, a = 6378136.3 m):
Topographic potential RWI_TOPO_2012 Download Mirror∂ICGEM Isostatic potential RWI_ISOS_2012 Download Mirror∂ICGEM Topographicisostatic potential RWI_TOIS_2012 Download Mirror∂ICGEM  To allow the evaluation of the RWI 2012 models by synthesis software that by default subtracts the coefficients of a normal gravity field, three additional versions are available:
Topographic potential + GRS80 RWI_TOPO_2012_plusGRS80 Download Mirror∂ICGEM Isostatic potential + GRS80 RWI_ISOS_2012_plusGRS80 Download Mirror∂ICGEM Topographicisostatic potential + GRS80 RWI_TOIS_2012_plusGRS80 Download Mirror∂ICGEM where the zonal harmonic coefficients of the GRS80 normal gravity field are added to the coefficients of the RWI model

Please acknowledge the use of the RWI 2012 models by citing Grombein et al. (2014)
Release 2015:
 RWI_TOPO_2015: Updated spherical harmonic representation of the Earth's topographic gravitational potential (N=2190)
 REQ_TOPO_2015: Consistent rockequivalent version using condensed DTMheights (N=2190)
Main features:
 Threelayer decomposition of the topography using the new 1′×1′ Earth2014 topography model (Hirt and Rexer 2015)
 Rigorous separate modeling of rock, water, and ice masses with layerspecific density values
 Rock: 2670 kg m^{3}, Water: 1030 kg m^{3} (Ocean), 1000 kg m^{3} (Inland) , Ice: 917 kg m^{3}
 Ellipsoidal arrangement of the topography using the GRS80 ellipsoid + geoid undulations as height reference surface
 Additional compilation of a consistent rockequivalent version REQ_TOPO_2015, in which DTMheights of water and ice masses are condensed to the constant rock density 2670 kg m^{3}
Further details are provided in Grombein et al. (2016).
Processing:
 Forward modelling in the space domain using tesseroid mass bodies (Grombein et al. 2013)
 Transformation of global gridded values to the frequency domain by applying harmonic analysis up to degree and order 2190
Model versions and download:
 Spherical harmonic coefficients of the RWI 2015 models are provided by two versions
(GM = 3.986004415e+14 m^{3} s^{2}, a = 6378136.3 m):
Topographic potential RWI_TOPO_2015 Download Mirror∂ICGEM Topographic potential
(using rockequivalent heights)REQ_TOPO_2015 Download Mirror∂ICGEM  To allow the evaluation of the RWI 2015 models by synthesis software that by default subtracts the coefficients of a normal gravity field, two additional versions are available:
Topographic potential + GRS80 RWI_TOPO_2015_plusGRS80 Download Mirror∂ICGEM Topographic potential + GRS80
(using rockequivalent heights)REQ_TOPO_2015_plusGRS80 Download Mirror∂ICGEM where the zonal harmonic coefficients of the GRS80 normal gravity field are added to the coefficients of the RWI model

Please acknowledge the use of the RWI 2015 models by citing Grombein et al. (2016)
References:

Bassin, C.; Laske, G.; Masters, G. (2000): The current limits of resolution for surface wave tomography in North America. EOS Trans AGU, 81. F897

Grombein, T.; Seitz, K.; Heck, B. (2013): Optimized formulas for the gravitational field of a tesseroid. Journal of Geodesy 87(7):645–660, DOI: 10.1007/s0019001306361

Grombein, T.; Luo, X.; Seitz, K.; Heck, B. (2014): A waveletbased assessment of topographicisostatic reductions for GOCE gravity gradients. Surveys in Geophysics 35(4):959–982, DOI: 10.1007/s1071201492831

Grombein, T.; Seitz, K.; Heck, B. (2016): The RockWaterIce topographic gravity field model RWI_TOPO_2015 and its comparison to a conventional rockequivalent version. Surveys in Geophysics 37(5):937–976, DOI: 10.1007/s1071201693760

Hirt, C.; Rexer, M. (2015): Earth2014: 1 arcmin shape, topography, bedrock and icesheet models – Available as gridded data and degree10,800 spherical harmonics. International Journal of Applied Earth Observation and Geoinformation 39:103–112, DOI: 10.1016/j.jag.2015.03.001

Pavlis, N.K.; Factor, J.K.; Holmes, S.A. (2007): Terrainrelated gravimetric quantities computed for the next EGM. Proc. 1st Int. Symposium IGFS: Gravity Field of the Earth, Special Issue 18, 318–323.
Contact:
Acknowledgement:
This research was funded by the German Federal Ministry of Education and Research under grant number 03G0726F within the REAL GOCE project of the GEOTECHNOLOGIEN Programme.