Asked by: Martin Glover, Canterbury
The entire planet has been mapped, but the resolution of the data for most of the ocean is much lower than for land. Only about five per cent of the ocean floor has been mapped to the equivalent of a 1:50,000 OS map. Radar doesn’t penetrate well through water, so maps must be compiled by ships with multibeam sonar. We have better maps of Mars than for most of the seabed.