{"id":910,"date":"2019-03-23T10:16:47","date_gmt":"2019-03-23T10:16:47","guid":{"rendered":"http:\/\/oceansofbiodiversity.blogs.auckland.ac.nz\/?p=910"},"modified":"2024-12-06T11:30:48","modified_gmt":"2024-12-06T10:30:48","slug":"the-ocean-floor-is-less-well-mapped-than-the-surface-of-other-planets","status":"publish","type":"post","link":"https:\/\/site.nord.no\/oceansofbiodiversity\/2019\/03\/23\/the-ocean-floor-is-less-well-mapped-than-the-surface-of-other-planets\/","title":{"rendered":"The ocean floor is less well mapped than the surface of other planets’"},"content":{"rendered":"

I have often read and heard it stated that the seabed is less well mapped than the surface of other planets. However, I had not noticed papers that provided evidence for this or cited primary sources. I thank Peter Harris and David Sandwell for providing links to the evidence that shows indeed maps of other planets (and at least one asteroid) are at a finer spatial resolution and with better coverage than our oceans.
\nPeter drew to my attention that:
\nYou can download from the web a 50 m Digital Terrain Model (DTM) of the surface of Mars<\/a>. The website states \u201cThe high-resolution images used have a resolution of 10 m\/pixel. The DTM elevation data derived from these images is provided in pixels of up to 50 m, with a height accuracy of 10 m<\/em>.\u201d
\nYou can download a 100 m Digital Terrain Model for the Moon<\/a>. Its website states \u201cWide-angle Camera (WAC) \u2026. stereo images from the one-year nominal mission and the first months of the science mission phase are combined to produce a near-global digital terrain model (DTM) with a pixel spacing of 100 m, the Global Lunar DTM 100 m, or GLD100. It covers \u2026.. , 98.2% of the entire lunar surface<\/em>.\u201d
\nPeter added:
\n\u201cFor the ocean floor we can\u2019t even get close to the resolution of these models. The resolution of the SRTM 30 arc second (Shuttle Radar Topography Mission<\/a>) DTM for the ocean is supposedly 1 km (Becker et al., 2009). A resolution of 1 km is 100 times lower resolution than the 100 m DTM of the moon and 400 times worse than Mars!
\nBut we don\u2019t really have a 1 km map for the ocean because even though the grid is 1 km, the underlying data are spaced much further apart in most places [1]<\/b><\/span><\/span>. The satellite altimetry data used by Smith and Sandwell (1997) to fill in the holes where actual soundings are missing provides +\/- 100 m vertical estimates at 12.5 km spacing. That is the worst-case scenario but still applies to big chunks of the ocean. So it is very safe to say that our maps of most of the ocean floor don\u2019t even come close to the resolution of maps we have of for the whole of the surfaces of Mars and the Moon.\u201d
\nDavid Sandwell brought to our attention that Mercury has also been mapped<\/a> at a resolution of\u00a0 665 m, ten times better than the seabed. For the latest bathymetry, “11% of the oceans is mapped by ships at 500 m or better resolution. The other 89% is mapped by satellite altimetry at a \u00bd wavelength resolution of 6 km.\u00a0 Mercury, Mars, and the Moon all have topographic maps that have much better than 1 km spatial resolution.\u00a0 Venus was mapped by radar altimetry where the footprint of the radar is ~10 km so the map is provided on about a 10 km grid but the \u00bd wavelength resolution is only about 20 km. This is slightly worse than the Earth at ~6 km.\u00a0Note that in terms of imaging Venus has about 200 m resolution globally which is much better than the coverage of the oceans.”
\nEven some asteroids are mapped at better resolution than our seabed, for example, Phobos has a 100 m\/pixel DTM (Willner et al. 2014).
\nI also thank Roger Sayre and Dawn Wright for the above conversation.
\nOther indicators of how challenging the ocean has been for exploration are these events: <\/span><\/strong><\/p>\n