GEBCO (General Bathymetric Chart of the Oceans) is the authoritative global bathymetric dataset, operated jointly by the International Hydrographic Organization and UNESCO's Intergovernmental Oceanographic Commission. For GIS professionals working in marine or coastal domains, GEBCO fills a gap that land-focused elevation products like SRTM and Copernicus DEM don't cover: the ocean floor.
Its seamless land-ocean grid means you can work across coastlines without stitching separate datasets together — essential for tsunami modeling, storm surge simulation, offshore energy siting, and submarine cable routing where the transition from land to seabed needs to be continuous.
The key thing to understand about GEBCO is data provenance. Only about a quarter of the ocean floor has been directly measured with modern multibeam sonar; the rest is interpolated from satellite gravity data, which captures large features but misses fine-scale topography. GEBCO ships a Source Identifier grid alongside the elevation data so you can see exactly which pixels come from direct survey and which are modeled — a critical distinction for any engineering or safety-critical application.
The annual release cycle, driven partly by the Seabed 2030 initiative, means coverage improves each year as new survey data is integrated, making it worth checking for updated grids rather than relying on older downloads.
