Tuesday, 17 January 2012

Thermal video of Concordia shipwreck

Poignant images from the Concordia shipwreck have been released taken with what I assume to a thermal camera mounted on a helicopter. They are described as 'night vision' but I think they are thermal (or composite), with a black and white palette that makes white cold and black warm. You can see the black (warm) passengers and crew making their way down the side of the cold (white) hull.

As you might imagine, the wreck of the Titanic a century ago triggered research into remote detection of icebergs, notably a bolometer with which the horizon can be scanned. Since the bolometer only needs to scan a single defined line it is practical to try and use such a device: a bolometer only detects temperature remotely at a single point. Unfortunately it didn't seem to work, presumably because icebergs are at pretty well the same temperature as the sea and so wouldn't show up with the kind of bolometers available a hundred years ago.

As late as 1934 the American liner Manhattan was fitted with a fog camera, which automatically took an infrared photograph ahead every 50 seconds and then developed and printed it. The hope being that this system would give an early warning of obstacles in haze and fog. The liner's captain reported that the system had indeed been useful in a blizzard and in fog but remarked that it could not be used at night until "ships, lighthouses, and buoys are equipped with infra-red beams". But it was already clear that infrared photography would not penetrate fog and a Times special correspondent, explaining how what could be photographed was dependent on particle size, commented that the Manhattan voyage had "not been suitably foggy for a real test to be made".

Modern thermal imaging cameras are very capable of distinguishing between sea and either objects floating or surface obstructions and the video gives some indication of this. Note that the exposed parts of the ship seem colder (lighter) than the surface of the sea.

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