Scripts to convert GEBCO bathymetry tiles to MBTiles
https://www.gebco.net/data_and_products/gridded_bathymetry_data/
https://github.com/alukach/vector-ocean
https://github.com/acalcutt/jaxa_AW3D30_to_MBTiles/
https://blog.mastermaps.com/2012/09/creating-seafloor-map-using-shaded.html