Earth2014 global topography (relief) model
Earth2014 is a freely-available suite of global topography, bathymetry and ice-sheet grids developed at Curtin University (Perth) and TU Munich (Hirt and Rexer 2015). The Earth2014 products, constructed based on newest topography data sets that were available in 2014, have been released in 2015. The Earth2014 grids offer topography data with global coverage at 1 arc-minute (about 1.8 km) spatial resolution and may be suitable for applications such as global gravity modelling, particularly forward modelling, geo-visualisation (Fig. 1) and geophysical studies.
Fig.1 : Global map of the 1 arc-min Earth2014 bedrock layer (BED), unit in metres
The topography layers (e.g., bedrock, surface topography, ice) are the primary product. A number of derived or auxiliary products are available such as (1) Earth shape models (surface heights w.r.t geocenter), (2) spherical harmonic series expansions of the gridded data with ultra-high resolution (harmonic degree 10800), (3) data set masks and (4) down-sampled grids of coarser resolution (5 arc-min).
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All Earth2014 data sets can be obtained via the repository
Please consult the readme-file for details on the data products and the various data formats (binary, GMT-grid).
The Earth2014 citation is:
Hirt, C. and Rexer, M. (2015) Earth2014: 1 arc-min shape, topography, bedrock and ice-sheet models - available as gridded data and degree-10,800 spherical harmonics, International Journal of Applied Earth Observation and Geoinformation 39, 103-112, doi:10.1016/j.jag.2015.03.001. PDF
Input data and model development
The Earth2014 model suite is based on the four input data sets (a) Bedmap2 (Fretwell et al. 2013) bedrock and ice data over Antarctica, (b) GBT v3 Greenland bedrock topography data over Greenland (Bamber et al. 2013), (c) SRTM30_PLUS v9 (Becker et al. 2009) bathymetry over the oceans and major inland lakes, and over land in high northern latitudes (except for Greenland), and (d) SRTM V4.1 Topography (Jarvis et al. 2008) over continents/islands (Fig. 2) The procedures used to combine the input data sets of Earth2014 are detailed in the Hirt and Rexer (2015) paper.
Fig.2 : Input data sets used in Earth2014: Bedmap2 (red), GBT (orange), SRTM V4.1 (green), SRTM30_PLUS (mid blue: oceans; dark blue: lakes; light blue: land topography).
Results and visual impressions of the Earth2014 products
Earth2014 topography data is provided in terms of the five layers SUR (lower interface of the atmosphere), BED (Earth relief without water and ice), TBI (topography over land, bathymetry over the oceans and top of ice-sheets over Antarctica and Greenland), ICE (ice thickness = ice sheet heights) and RET (rock-equivalent topography). Selected Earth2014 layers are shown in Fig. 3. Degree variances computed from the degree-10800 spherical harmonic expansions of the Earth2014 grids are displayed in Fig. 4.
Differences between the Earth2014 topography (heights relative to the mean sea level) and shape grids (geocentric radii relative to the geocenter) are shown in Fig. 5. The right panel nicely shows the (geometrical) shape of planet Earth, a lesser known perspective on our planet.
Fig.3 : 3D visualisations of the Earth2014 SUR, BED, TBI and RET topography layers over the Southern Hemisphere, centred to Antarctica.
Fig.4 : Global degree variance spectra of the five Earth2014 layers to degree 10,800
Fig.5 : Earth2014 relief model: Heights relative to the mean sea level (left) and distances of surface points from the geocentre (right).
This work has been supported by the TUM Institute for Advanced Study. All data providers are kindly acknowledged.
Bamber, J.L. et al. (2013), A new bed elevation dataset for Greenland. The Cryosphere, 7, 499-510.
Becker, J.J., D.T. Sandwell, W.H.F. Smith, et al. (2009), Global Bathymetry and Elevation Data at 30 Arc Seconds Resolution: SRTM30_PLUS. Marine Geodesy 32(4): 355-371.
Fretwell, P. et al. (2013), Bedmap2: improved ice bed, surface and thickness datasets for Antarctica, The Cryosphere, 7, 375-393.
Hirt, C. and M. Rexer (2015), Earth2014: 1 arc-min shape, topography, bedrock and ice-sheet models - available as gridded data and degree-10,800 spherical harmonics, International Journal of Applied Earth Obs. and Geoinf.n 39, 103-112. PDF
Jarvis, A., H.I. Reuter, A. Nelson, and E. Guevara (2008), Hole-filled SRTM for the globe Version 4, Available from the CGIAR-CSI SRTM 90m database : http://srtm.csi.cgiar.org.