------------------------------------------------------------------------------------------ ----------------------- Readme for Earth2014 potential models ---------------------------- ------------------------------------------------------------------------------------------ date: 24/08/2016 author: Moritz Rexer email: m.rexer@tum.de citation: Rexer M, Hirt C, Claessens S, Tenzer R (2016) Layer-based modelling of the Earth's gravitational potential up to 10km scale in spherical harmonics in spherical and ellipsoidal approximation, Surveys in Geophysics, DOI :10.1007/s10712-016-9382-2. ------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------ 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 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. For details on the computational procedure and for more information on the differences between STP and ETP we refer to Rexer et al.(2016) and Claessens and Hirt (2013). The models are available here: http://ddfe.curtin.edu.au/models/Earth2014/potential_model/ ------------------------------------------------------------------------------------------ 2. List of models and model parameters Acronym & Approximation & Layer & Layer Approach & Max. Degree dV_ELL_Earth2014 & ellipsoidal/ETP & all & LRA & 2190 dV_ELL_ICE2014 & ellipsoidal/ETP & Ice-layer & LRA & 2190 dV_ELL_LAKES2014 & ellipsoidal/ETP & Lakes-layer & LRA & 2190 dV_ELL_OCEAN2014 & ellipsoidal/ETP & Ocean-layer & LRA & 2190 dV_ELL_CRUST2014 & ellipsoidal/ETP & Crust-layer & LRA & 2190 dV_ELL_RET2014 & ellipsoidal/ETP & all & RET & 2190 dV_SPH_Earth2014 & spherical/STP & all & LRA & 2160 dV_SPH_ICE2014 & spherical/STP & Ice-layer & LRA & 2160 dV_SPH_LAKES2014 & spherical/STP & Lakes-layer & LRA & 2160 dV_SPH_OCEAN2014 & spherical/STP & Ocean-layer & LRA & 2160 dV_SPH_CRUST2014 & spherical/STP & Crust-layer & LRA & 2160 dV_SPH_RET2014 & spherical/STP & all & RET & 2160 RET: Rock-Equivalent-Topography, LRA: Layer-Reduction-Approach ------------------------------------------------------------------------------------------- 3. Binary SHC file format (.bshc) The spherical harmonic coefficients (SHCs) are stored in binary format as double and big endian. The file structure is: n_min n_max (minimum and maximum harmonic degree) C-coefficients ascending in degree, followed by the order S-coefficients ascending in degree, followed by the order Example for a degree-10800 file: 0 10800 C(0,0), C(1,0), C(1,1), C(2,0), C(2,1), ... C(10800,10799), C(10800,10800), ,S(0,0), S(1,0), S(1,1), S(2,0), S(2,1), ... S(10800,10799), S(10800,10800). The matlab routine read_SHCs_bshc2tri.m reads the coefficients from the .bshc file into a matrix with triangle form. The routine is avialable here: http://ddfe.curtin.edu.au/models/Earth2014/software/read_SHCs_bshc2tri.m -------------------------------------------------------------------------------------------- References: Hirt C, Rexer M (2015) Earth2014: 1' shape,topography,bedrock and ice-sheet models - Available as gridded data and degree 10,800 spherical harmonics. International Journal of Applied Observation and Geoinformation, DOI:10.1060/j.jag2015.03.001. Claessens S, Hirt C (2013) Ellipsoidal Topographic Potential - new solutions for spectral forward modelling of topography with respect to a reference ellipsoid. Journal of Geophysical Research 118(11):5991-6002, DOI 10.1002/2013JB010457. -------------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------------