The GEBCO_2021 Grid is a global terrain model for ocean and land, providing elevation data, in meters, on a 15 arc-second interval grid. It includes a number of additonal data sets compared to the GEBCO_2020 Grid.
The grid is accompanied by a Type Identifier (TID) Grid, giving information on the types of source data that the GEBCO_2021 Grid is based on.
The primary GEBCO_2021 grid contains land and ice surface elevation information - as provided for previous GEBCO grid releases. In addition, for the 2021 release, we have made available a version with under-ice topography/bathymetry information for Greenland and Antarctica.
The GEBCO_2021 Grid provides global coverage of elevation data in meters on a 15 arc-second grid of 43200 rows x 86400 columns, giving 3,732,480,000 data points.
The GEBCO Grid is accompanied by a Type Identifier (TID) grid. This data set identifies the type of source data that the corresponding grid cells in the GEBCO Grid are based on. Further information about the format and coding of the TID grid is given below.
|10||Singlebeam - depth value collected by a single beam echo-sounder|
|11||Multibeam - depth value collected by a multibeam echo-sounder|
|12||Seismic - depth value collected by seismic methods|
|13||Isolated sounding - depth value that is not part of a regular survey or trackline|
|14||ENC sounding - depth value extracted from an Electronic Navigation Chart (ENC)|
|15||Lidar - depth derived from a bathymetric lidar sensor|
|16||Depth measured by optical light sensor|
|17||Combination of direct measurement methods|
|40||Predicted based on satellite-derived gravity data - depth value is an interpolated value guided by satellite-derived gravity data|
|41||Interpolated based on a computer algorithm - depth value is an interpolated value based on a computer algorithm (e.g. Generic Mapping Tools)|
|42||Digital bathymetric contours from charts - depth value taken from a bathymetric contour data set|
|43||Digital bathymetric contours from ENCs - depth value taken from bathymetric contours from an Electronic Navigation Chart (ENC)|
|44||Bathymetric sounding - depth value at this location is constrained by bathymetric sounding(s) within a gridded data set where interpolation between sounding points is guided by satellite-derived gravity data|
|45||Predicted based on helicopter/flight-derived gravity data|
|46||Depth estimated by calculating the draft of a grounded iceberg using satellite-derived freeboard measurement.||Unknown|
|70||Pre-generated grid - depth value is taken from a pre-generated grid that is based on mixed source data types, e.g. single beam, multibeam, interpolation etc.|
|71||Unknown source - depth value from an unknown source|
|72||Steering points - depth value used to constrain the grid in areas of poor data coverage|
The complete GEBCO_2021 data set provides global coverage, spanning 89° 59' 52.5''N, 179° 59' 52.5''W to 89° 59' 52.5''S, 179° 59' 52.5''E on a 15 arc-second geographic latitude and longitude grid. It consists of 43200 rows x 86400 columns, giving 3,732,480,000 data points. The data values are pixel-centre registered i.e. they refer to elevations, in meters, at the centre of grid cells.
The GEBCO grid can be assumed to be relative to WGS84.
GEBCO's global elevation models are generated by the assimilation of heterogeneous data types, assuming all of them to be referred to Mean Sea Level. However, in some shallow water areas, the grids include data from sources having a vertical datum other than mean sea level.
The GEBCO_2021 NetCDF files are provided in NetCDF 4 format and conform to the NetCDF Climate and Forecast (CF) Metadata Convention v1.6 (http://cfconventions.org/).
Within the NetCDF files, the GEBCO_2021 gridded data are stored as a two-dimensional array of 2-byte integer values of elevation in metres, with negative values for bathymetric depths and positive values for topographic heights. The GEBCO_2021 TID grid is provided in the NetCDF format, but data are stored as a two-dimensional array of single byte integers.
If the data sets are used in a presentation or publication then we ask that you acknowledge the source.This should be of the form:
GEBCO Compilation Group (2021) GEBCO 2021 Grid (doi:10.5285/c6612cbe-50b3-0cff-e053-6c86abc09f8f)
The GEBCO Grid is placed in the public domain and may be used free of charge.
Use of the GEBCO Grid indicates that the user accepts the conditions of use and disclaimer information given below.
While every effort is made to produce an error free grid, some artefacts may still appear in the data set. Please see our errata page for information on known bugs in the dataset.