MadSci Network: Earth Sciences
Query:

Re: What caused this underwater scarring?

Date: Mon Jan 4 14:44:59 2010
Posted By: James R Holliday, Physics Department
Area of science: Earth Sciences
ID: 1258607199.Es
Message:

Doug,

Greetings. When Google added high-resolution surface depth images to Google Maps and Google Earth in early 2009, the Internet community was quick to uncover interesting patterns. Most of these, however, can be explained by faulty image processing and artifacts in the data.

The grid lines you refer to are most likely a processing artifact. Most of the data comes from satellite measurements of gravity. The gravity data are cross-checked against ship sonar tracks from a variety of vessels. This type of grid pattern is typical for a research vessel surveying a patch of ocean floor. The gravity data and sonar data donít always match up perfectly so you get these artifacts along the edges of the ship sonar.

At the http://googlesightseeing.com/ link above, user LarryM makes the following statement:

Iím an oceanographer. I can tell you the grid pattern is simply the location where a ship has been to collect high-resolution data. In most places, the seafloor bathymetry is deduced from satellite measurement of the sea surface. Itís the ďpredicted bathymetryĒ, a good guess, but still, not as reliable as a direct measurement. In this case, some ship went there, collected bathymetry, but it seems that it didnít agree exactly with predicted bathymetry, so the ship tracks appear as a grid. It shows how poorly known the seafloot really is! There are many other places where similar tracks are found (for example see a bit to the east). The tracks are particularly visible where the seafloor is sedimented and very smooth, like here. As for the irregularity, itís a function of targeting study locations and minimizing the time (and cost) of the survey.

which pretty much sums it up.

I hope this answers your question.

Cheers,

James R Holliday


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