Ultra-high resolution
Ultra-high resolution modelling of Earth’s gravity field
Our research activities focus on ultra-high resolution (e.g. ~200 m or below) modelling of Earth’s gravity field, particularly through use of gravity forward-modelling techniques. Notable outcomes of our modelling activities are:
- Global Gravity Field Model plus (GGMplus) resolves the Earth’s gravity field near-globally to ~200m spatial scales based on GRACE, GOCE, EGM2008 and SRTM topography data.
Data
Data access
The GGMplus gravity field model is freely available from our FTP-Server. Due to its total size of 75 GB, the model is partitioned and distributed in 881 binary files of 5 deg x 5 deg size for each functional (gravity accelerations, gravity disturbances).
A list of all tiles can be accessed here.
Format description
Each 5 deg x 5 deg tile contains 2500×2500 grid points in centre-of-cell representation. The grid resolution is 0.002 deg (7.2 arc seconds) with the grid equally spaced in terms of geodetic (GRS80) latitude and longitude.
Depending on the functional, data is stored either in 2-byte integer big-endian format (int16, ieee-be), or 4-byte big-endian format (int32, ieee-be). Vertical deflections (xi, eta) and gravity disturbances (dg) are in 2-byte format, quasigeoid heights and gravity accelerations in 4-byte format. The file sizes are 12,208 KB and 24,416 KB, respectively.
The readme-document provides full details on the file formats.
- ERTM2160 is the high-frequency component of GGMplus and can be used to augment spherical harmonic models beyond degree 2160.
Data
Data access
The ERTM2160 gravity field model is freely available from our Digital Data FrontEnd server. Due to its total size of 75 GB, the model is partitioned and distributed in 881 binary files of 5 deg x 5 deg size for each functional (gravity accelerations, gravity disturbances).
A list of all tiles can be accessed here.
Format description
Each 5 deg x 5 deg tile contains 2500×2500 grid points in centre-of-cell representation. The grid resolution is 0.002 deg (7.2 arc seconds) with the grid equally spaced in terms of geodetic (GRS80) latitude and longitude. All data is stored in 2-byte integer big-endian format (int16, ieee-be).
The readme-document provides full details on the file formats.
- EurAlpGM2011 is a prototype model of the gravity field over the European Alps area, showing the detail variations in gravity field quantities over a mountainous area.
Data
- EurAlpGM2011 quasigeoid heights (sum of EGM2008 band of spherical harmonic degrees 2 to 2190 and ERTM2160 quasigeoid heights, unit in mm)
Download - EurAlpGM2011 gravity disturbance (sum of EGM2008 band 2 to 2190 and ERTM2160 gravity disturbances, unit in 0.1 mGals)
Download - EurAlpGM2011 North-South vertical deflection (sum of EGM2008 band 2 to 2190 and ERTM2160 N-S deflections, unit in 0.1 arc seconds)
Download - EurAlpGM2011 East-West vertical deflection (sum of EGM2008 band 2 to 2190 and ERTM2160 N-S deflections, unit in 0.1 arc seconds)
Download - Normal gravity (at the surface of terrain as defined by the SRTM ellipsoidal heights, unit of normal gravity in 0.1 mGal)
Download - Surface gravity accelerations (sum of normal gravity and EurAlpGM2011 gravity disturbances, unit in 0.1 mGal)
Download - Total vertical deflections (defined as square-root of the sum of squared EW and NS deflections, unit in 0.1 arc seconds)
Download - EGM2008 quasigeoid height (unit mm)
Download - EGM2008 gravity disturbance (unit 0.1 mGal)
Download - EGM2008 North-South deflection (unit 0.1 arc seconds)
Download - EGM2008 East-West deflection (unit 0.1 arc seconds)
Download - ERTM2160 quasigeoid height (unit mm)
Download - ERTM2160 gravity disturbance (unit 0.1 arc seconds)
Download - ERTM2160 North-South deflection (unit 0.1 arc seconds)
Download - ERTM2160 East-West deflection (unit 0.1 arc seconds)
Download
GGMplus (Global Gravity Model plus) is a composite model that refines existing gravity models from spacecraft-tracking and terrestrial data (GRACE, GOCE and EGM2008) with high-resolution topographic gravity information derived from SRTM topography data. GGMplus provides maps and data of Earth’s gravity at 200 m resolution for all land and near-coastal areas of our planet between +- 60° latitude. Past gravity field modelling efforts either placed focus on global coverage with limited resolution or on representation of local detail over regionally limited areas. GGMplus and ERTM2160 are the first models of Earth’s gravity field to reach local resolution with near-global coverage.
ERTM2160 has been employed to study signal strengths of the Earth’s short scale gravity field. The model can be used as short-scale augmentation to any degree-2160 global geopotential model.
Contributors
- Dr Christian Hirt
- Dr Sten Claessens
- Prof William Featherstone
- Associate Professor Michael Kuhn
- Prof Roland Pail, Dr Kurt Seitz, Dr Thomas Gruber, MSc Moritz Rexer