GEBCO Earth Reliefs

Usage

You access the GEBCO global relief grid by specifying the special name

@earth_gebco[_rru[_reg]]

This grid only contains observed relief and inferred relief via altimetric gravity. A second grid that gives sub-ice (si) elevations is also available and can be accessed via

@earth_gebcosi[_rru[_reg]]

and is the one displayed above. The following codes for rru and the optional reg are supported (dimensions are listed for pixel-registered grids; gridline-registered grids increment dimensions by one):

Code	Dimensions	Reg	Size	Description
01d	360 x 180	g,p	103 KB	1 arc degree global relief (GEBCO 2025 @ 315 km)
30m	720 x 360	g,p	350 KB	30 arc minute global relief (GEBCO 2025 @ 157 km)
20m	1080 x 540	g,p	729 KB	20 arc minute global relief (GEBCO 2025 @ 105 km)
15m	1440 x 720	g,p	1.3 MB	15 arc minute global relief (GEBCO 2025 @ 79 km)
10m	2160 x 1080	g,p	2.7 MB	10 arc minute global relief (GEBCO 2025 @ 52 km)
06m	3600 x 1800	g,p	7.1 MB	6 arc minute global relief (GEBCO 2025 @ 32 km)
05m	4320 x 2160	g,p	10 MB	5 arc minute global relief (GEBCO 2025 @ 26 km)
04m	5400 x 2700	g,p	16 MB	4 arc minute global relief (GEBCO 2025 @ 21 km)
03m	7200 x 3600	g,p	27 MB	3 arc minute global relief (GEBCO 2025 @ 16 km)
02m	10800 x 5400	g,p	58 MB	2 arc minute global relief (GEBCO 2025 @ 11 km)
01m	21600 x 10800	g,p	211 MB	1 arc minute global relief (GEBCO 2025 @ 1.9 km)
30s	43200 x 21600	g,p	752 MB	30 arc second global relief (GEBCO 2025 @ 2.6 km)
15s	86400 x 43200	p	2.6 GB	15 arc second global relief (GEBCO 2025 original)
03s	432000 x 216000	g	6.8 GB	3 arc second global relief (SRTM3S original)
01s	1296000 x 432000	g	41 GB	1 arc second global relief (SRTM1S original)

Note that resolutions 05m and higher are tiled. See Remote Datasets for more information.

See GMT remote dataset usage for when resolution codes are optional or required. All of these data will, when downloaded, be placed in your ~/.gmt/server directory, with the earth_gebco files being placed in an earth/earth_gebco sub-directory, and earth_gebcosi files in an earth/earth_gebcosi sub-directory. If you do not specify a CPT then the default CPT (the GMT master geo CPT) will be used.

Examples

To create a PDF map of the GEBCO global relief at 1 arc degree resolution, try:

gmt grdimage @earth_gebco_01d -Baf -pdf earth_gebco

Technical Information

As you see, the 30s and lower resolutions are all derivatives of GEBCO’s 2025 15 arc second grids (GEBCO_Compilation_Group, 2025). We have downsampled it via Cartesian Gaussian filtering to prevent aliasing while preserving the latitude-dependent resolution in the original 15 arc sec grid. The full (6 sigma) filter-widths are indicated in parenthesis. The 3 and 1 arc second data are the SRTM 1x1 degree tiles from NASA. Note: The 3 and 1 arc second grids only extend to latitudes ±60˚ and are only available over land. When these grids are accessed as @earth_gebco_01s or @earth_gebco_03s we will automatically up-sample the relevant @earth_gebco_15s tiles to fill in the missing ocean values. If you just want the original land-only SRTM tiles you may use the special names @srtm_relief_03s or @srtm_relief_01s instead. Almost all grids are available in both gridline- and pixel-registered formats except the original pixel-registered GEBCO 2025 (here called @earth_gebco_15s) and the gridline-registered SRTM tiles.

We also scale and reformat the original data to take up very little space so that downloads from the servers are as fast as possible. For the earth_gebco grids this means we chose 1 meter as the grid z step, which is well below the uncertainties in the data. Elevations are stored in a short integer grid that is highly compressed by netCDF lossless compression and chunking. The 3 and 1 arc second SRTM tiles are instead served as losslessly compressed JPEG2000 tiles whose grid z step is 1 meter.

Note: Because of this quantization, these grids should be used with care in morphometric studies (e.g., slope, curvature or roughness analyses), since even sub-meter rounding can bias slope and aspect calculations [Carter, 1992]. We suggest using the original dataset instead for such applications.

Data References

1. Carter, J.R., 1992: [https://doi.org/10.3138/aj35-34h3-524k-0685].

2. GEBCO Compilation Group (2025) GEBCO 2025 Grid (https://doi.org/10.5285/37c52e96-24ea-67ce-e063-7086abc05f29)

3. SRTMGL3 tiles: [https://lpdaac.usgs.gov/products/srtmgl3v003].

4. SRTMGL1 tiles: [https://lpdaac.usgs.gov/products/srtmgl1v003].