• IHO Logo
  • IOC of UNESCO Logo

GEBCO_2021 Grid

  • IHO Logo
  • IOC of UNESCO Logo

The GEBCO_2021 Grid

GEBCO_2021 Grid

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.

Please see the accompanying documentation for more information Adobe PDF of the documentation to accompany the GEBCO_2021 Grid (1 MB).


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 data are available to download according to the Terms of Use provided below.

GEBCO Type Identifier (TID) Grid

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.

TID Definition
0 Land
Direct measurements
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
Indirect measurements
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.
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

GEBCO Grid, vertical and horizontal datum

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.

Data Dissemination

CF-compliant NetCDF format

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.

  • The global dataset is provided as a single 7.5 GB file
  • The global TID grid is provided as a single 4 GB file

Data set attribution

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)

Terms of use and disclaimer


  • These terms of use apply to The GEBCO Grid and other GEBCO-derived information products
  • For brevity ‘The GEBCO Grid’ is used throughout and should be interpreted as meaning The GEBCO Grid and other GEBCO-derived information products
  • Bathymetric Data refers to measurements made by various instruments of the ocean depth, associated ocean properties and the supporting metadata
  • Information products are the result of applying algorithms, mathematical techniques, scientific theory and Intellectual Property to data to create useful, derived values
  • As the GEBCO Grid is created by interpolating, applying algorithms and mathematical techniques to bathymetric data, GEBCO considers the GEBCO Grid to be an information product
  • GEBCO does not provide the underlying source bathymetric data when distributing the GEBCO Grid

Terms of use

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.

Users are free to:

  • Copy, publish, distribute and transmit The GEBCO Grid
  • Adapt The GEBCO Grid
  • Commercially exploit The GEBCO Grid, by, for example, combining it with other information, or by including it in their own product or application

Users must:

  • Acknowledge the source of The GEBCO Grid. A suitable form of attribution is given in the documentation that accompanies The GEBCO Grid.
  • Not use The GEBCO Grid in a way that suggests any official status or that GEBCO, or the IHO or IOC, endorses any particular application of The GEBCO Grid.
  • Not mislead others or misrepresent The GEBCO Grid or its source.


  • The GEBCO Grid should NOT be used for navigation or for any other purpose involving safety at sea.
  • The GEBCO Grid is made available 'as is'. While every effort has been made to ensure reliability within the limits of present knowledge, the accuracy and completeness of The GEBCO Grid cannot be guaranteed. No responsibility can be accepted by GEBCO, IHO, IOC, or those involved in its creation or publication for any consequential loss, injury or damage arising from its use or for determining the fitness of The GEBCO Grid for any particular use.
  • The GEBCO Grid is based on bathymetric data from many different sources of varying quality and coverage.
  • As The GEBCO Grid is an information product created by interpolation of measured data, the resolution of The GEBCO Grid may be significantly different to that of the resolution of the underlying measured data.

Reporting bugs in the GEBCO Grid

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.

If you find any anomalies in the grid then please report them via email (), giving the problem location, and we will investigate.