------------------------------------------------------------------------------------------------------ ----------------------- Readme for degree-5400/5480 Earth2014 potential models ----------------------- ------------------------------------------------------------------------------------------------------ date: 13/03/2018 author: Dr. Moritz Rexer email: m.rexer@tum.de department: Institute for Astronomical and Physical Geodesy institution: Technische Universitaet Muenchen citation: Rexer, M. (2017) Spectral Solutions to the Topographic Potential in the context of High-Resolution Global Gravity Field Modelling, Dissertation, Technische Universitaet Muenchen, http://mediatum.ub.tum.de?id=1349781. or Rexer M., Hirt C. and Pail R. (2017) High-resolution global forward modelling - A degree-5480 global ellipsoidal topographic potential model, EGU2017-7725, European Geosciences Union General Assembly 2017, Vienna, 25/04/2017. ----------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------- 1. General The gravitational potential has been forward modelled by spectral integration of volumetric mass layers as represented by the Earth2014 (Hirt and Rexer, 2015) topographic database. Potential models for each layer (crust, ocean, ice,lakes) and for their combined effect (=Earth) are available explicitly as a series of spherical harmonic coefficients of the spherical topographic potential (STP) and the ellipsoidal topographic potential (ETP), relying on spherical and ellipsoidal approximation, respectively. A full convergence of the binominal series expansions during the modelling was ensured. The k-series was taken up to the 25th order, and the j-series was taken up to the 40th order. Due to the latter the model contains a "tail" of 80 coefficients at the end, exceeding the actual maximum degree of the topographic layers, which was 5400. Due to the ellipsoidal-appoximation (ETP) in the spherical harmonic model, the model may not be truncated at degrees below the maximum degree nmax without suffering of severe errors at high latitutes. Therefore it is recommended to use the models only up to their maximum degree. On request the author is happy to provide spherical-approximation (STP) equivalents of the models that may be truncated at n