The Gaps in the Maps

Geomorphology provides the basic information necessary to interpret landscapes and their development. But it is not always simple to obtain topographic data. Remote areas which are difficult to access require advanced technologies and extensive funding. This is obvious for the surface of distant planets but… What about our ocean floor?

comparison res
Compared to surface images of Mars like Crommelin Crater (details from HRSC image 3264_0000 in right image) our maps of the better studied Whittard Canyon (S of Ireland) appears quite blurry. Scale bar left: 20 km; right: 4 km.

Apparently we have a better idea of the surface structures of Mars than of our own planet’s ocean floor. The MOLA-DTM (digital terrain model) provides basic topographical information on the Martian surface while an increasing part of it is also captured in high resolution images of less than 1 m/pixel. More precisely, today almost 90% of the Martian surface is mapped in high resolution with over half of it with a resolution better than 20 m/pixel. By now even individual crystals are visible.

mars coverage
A net of high resolution data covers almost 90% of the Martian surface (image courtesy of FU Berlin and ESA)

So what about the ocean floor? It seems so much closer… Yet actually only approximately 5% of the ocean floor has been mapped to a certain extent so far. This leaves us with around 65% of the surface of the Earth UNEXPLORED! Most of the area covered is found along  coastlines and commercial routes; with major gaps in the middle of the oceans and in Polar Regions. This is e.g. one of the reasons why there is no further confirmation for some of the modelled plastic garbage patches in less frequented regions. Many research vessels nowadays are equipped with multi-beam sonar which provides topographical data of the sea floor at a good resolution and high vertical accuracy. However, this coverage is again only achieved in close proximity to the ship’s route. Areas that are not in the focus of research are covered by satellite altimetry at a much lower resolution and accuracy. The global marine coverage by multi-beam tracks can be retraced on NOAA maps.

atlantic coverage
A map of multi-beam tracks (between 1980 and today) across the North Atlantic reveals the actual coverage at a higher resolution for a ‘well frequented’ ocean (NOAA).

ESRI offers access to a basic ocean basemap for ArcGIS with higher resolution for the U.S. and some other mainly coastal areas which are more accessible and have, therefore, often been studied in more detail. Researchers working in marine regions around Ireland like the Rockall Trough, the Porcupine Seabight or the Whittard Canyon are in luck. Not only is there a map with higher coverage of Ireland’s marine area available from the INFOMAR programme, a joint venture between Marine Institute (MI) and Geological Survey Ireland (GSI); the last years also produced high resolution maps of selected areas especially in connection with deep sea corals and biodiversity.

For less popular areas it might take a while before all features will be revealed…

IMG_5710
… and until then we can only guess what lies ‘beyond’

Authored by Alexandra Oppelt, PhD student, Biogeochemistry Research Group, TCD

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