Using Landsat Imagery to Find Shipwrecks

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What do treasure hunters and historians have in common? They both want to find shipwrecks.  Researchers estimate there could be nearly three million ships on the bottom of the ocean, and only about 10% of all shipwrecks have ever been found. Some of these ships are rumored to hold billions in buried treasure, while others hold a different form of treasure: history.

One way treasure hunters, archeologists, historians and others are finding shipwrecks is by using satellite imagery. Two current tactics for finding non-natural material at the bottom of the sea, like wood or metal used in ship, are: using waterborne sonar or airborne LiDAR. Both systems have their benefits and detractions, but neither are particularly good when it comes to finding wrecks in shallow, cloudy water.

This is, unfortunately, where many ships have wrecked. Ships usually wreck near harbors when they run into rocks or sandbars and can be sunk in very shallow waters, which aren’t always clear enough to see through. Researchers are using satellites to figure out new ways to detect wrecked ships in shallow water around the world, and are finding some success doing just that.

Satellite imagery from Landsat 8 has been used by a Belgian marine research institute to detect shallow water shipwrecks. The crew took a look at four known shipwrecks off the Belgian coast in order to find out how they could detect other shipwrecks using satellite imagery. The research team realized that, like other natural features underwater, shipwrecks changed the geography of the sea floor as well as the composition of the seawater around them. Satellite imagery from Landsat 8 can detect the concentration of sand and silt particles in the ocean, which can then be used to pinpoint a potential shipwreck location.

These satellite images were acquired by the Operational Land Imager (OLI) on Landsat 8 on April 1, 2014. In these natural-color views, long sediment plumes extend from the known wreck sites of the Sansip and Samvurn.  Source: NASA.
These satellite images were acquired by the Operational Land Imager (OLI) on Landsat 8 on April 1, 2014. In these natural-color views, long sediment plumes extend from the known wreck sites of the Sansip and Samvurn. Source: NASA.

The wrecks that were analyzed by the Belgian research team showed long plumes of sand and silt coming off of the ships because of the movement of water, which could be detected from space.

Elevation models show the SS Sansip (left) and the SS Samvurn (right) as imaged by a multibeam echosounder. Both of these ships leave sediment plumes detectable by Landsat 8 during ebb and flood tides.  Source: Matthias Baeye et al
Elevation models show the SS Sansip (left) and the SS Samvurn (right) as imaged by a multibeam echosounder. Both of these ships leave sediment plumes detectable by Landsat 8 during ebb and flood tides. Source: Matthias Baeye et al

The researchers weren’t sure if the satellite data would be the same on wooden ships or in different depths: their shipwrecks were all metal and located at a depth of 15 meters.

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Satellites and Shipwrecks: Landsat Satellite Spots Foundered Ships in Coastal Waters.  Rocchio, L, NASA, March 11, 2016.

Baeye, M., et al. (2016) Detection of shipwrecks in ocean colour satellite imagery. Journal of Archaeological Science,66:1-6.

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