Tuesday, February 7, 2012

New bathymetry in Google Earth

Global seafloor update in Google Earth
To see more of what's changed, Google has created this short video to give you a tour

From Scripps

Internet information giant Google updated ocean data in its Google Earth application this week, reflecting new bathymetry data assembled by Scripps Institution of Oceanography, UC San Diego, NOAA researchers and many other ocean mapping groups from around the world.

The newest version of Google Earth includes more accurate imagery in several key areas of ocean using data collected by research cruises over the past three years.

"The original version of Google Ocean was a newly developed prototype map that had high resolution but also contained thousands of blunders related to the original archived ship data," said David Sandwell, a Scripps geophysicist.
"UCSD undergraduate students spent the past three years identifying and correcting the blunders as well as adding all the multibeam echosounder data archived at the National Geophysical Data Center in Boulder, Colorado."

The Mediterranean Sea: before (left) and after (right) Example of a place you’ll notice an improvement in the ocean terrain data is the Mediterranean Sea, particularly south of Cyprus, where the boundary between the Eurasian and Arabian plates is now more clearly defined.

"The Google map now matches the map used in the research community, which makes the Google Earth program much more useful as a tool for planning cruises to uncharted areas," Sandwell added.

Previous terrain data showed what appeared to be a city grid on the ocean floor (left), which was confused for the lost city of Atlantis.
Updated data more accurately reflects the seafloor terrain (right).

For example, the updated, more precise data corrects a grid-like artifact on the seafloor that was misinterpreted in the popular press as evidence of the lost city of Atlantis off the coast of North Africa.

Guam and Mariana’s Trench before (left) and after (right)
Our last example shows improvements to the land-sea mask along the coastline of Guam.
You’ll notice a dramatic improvement in the resolution of both the coastline and neighboring Mariana’s Trench, the deepest trench in the world.

Through several rounds of upgrades, Google Earth now has 15 percent of the seafloor image derived from shipboard soundings at 1-kilometer resolution.
Previous versions only derived about 10 percent of their data from ship soundings and the rest from depths predicted by Sandwell and NOAA researcher Walter Smith using satellite gravity measurements.
The two developed the prediction technique in 1994.
The satellite and sounding data are combined with land topography from the NASA Shuttle Radar Topography Mission (SRTM) to create a global topography and bathymetry grid called SRTM30_PLUS.
On 11th January 2012, Google replaced its global bathymetry SRTM30_PLUS V4.0 with the newer version V7.0.
This has increased the area of seafloor covered at 1km resolution from 10% to 15%.
The new version also corrected thousands of errors in the old data and includes all of the multibeam bathymetry data collected by U.S. research vessels over the past three decades including 287 Scripps expeditions from research vessels Washington, Melville and Revelle.
UCSD undergraduate student Alexis Shakas processed all the U.S. multibeam data and then worked with Google researchers on the global integration.

The next major upgrade to the grid will occur later this year using a new gravity model having twice the accuracy of previous models.
The new gravity information is being collected by a European Space Agency satellite called CryoSat that was launched in February 2010.

Data from Scripps, NOAA sharpen resolution of seafloor maps.

By visiting Google Earth, you can use the 'historical imagery' flag to see old versus new.
This KLM File shows some improvements and differences, like Atlantis being less clearly visible, the improvements offshore Ireland and the Mariana Trench, as well as in the Californian Gulf, Great Barrier Reef and the Clarian fracture zone in the Pacific.
Also a sea mount that was vague now is made visible.

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