Colvocoresses Reef
Colvocoresses Reef is a wholly submerged atoll in the Indian Ocean, located in the north-eastern part of the Chagos Archipelago, near Speakers Bank and Blenheim Reef in the British Indian Ocean Territory.[1] The reef is five miles long, and measures half a mile to a mile across.[2] Breakers are visible only during heavy seas.
History
This submerged atoll is named after Alden Partridge Colvocoresses who in the 1970s together with John P. Snyder and John L. Junkins developed the Space-oblique Mercator projection.
The least charted depth is 30 feet above the reef. This sounding was one of only a few that were ever incorporated into US nautical charts, having been derived not from sonar or lead line data, but from radiometric data from the Landsat Multispectral Scanner (MSS) imagery.[3]
Colvocoresses Reef is unique in that it was discovered by use of images taken by the National Aeronautics and Space Administration's (NASA) Landsat Satellite.
The original depth data for the shallow water areas on Chagos Archipelago nautical charts had been collected in the mid-1830s. Except for the areas around Diego Garcia, much of the data on the current small-scale charts of the archipelago is from the 1830s data. In 1975, an American agency, the Hydrographic Center of the Defense Mapping Agency, requested NASA to collect Landsat images over the Chagos Archipelago. The images revealed the previously uncharted Colvocoresses Reef as well as errors in positioning of numerous other reefs in the Archipelago. Some were out of position by as much as 11 miles.
Notice to mariners
The brightness of the reef was compared with the brightness of other reefs that had known depths and similar bottom reflections. It was deemed advisable to give in a notice to mariners a probable depth range for the reef with a caution on the chart that there were probably shallower features on the reef.[4]
References
- ↑ British Admiralty nautical chart 11000030 - 3 Chagos Archipelago, Scale 1:360 000
- ↑ "Oceandots - Colvocoresses Reef". Archived from the original on December 23, 2010. https://web.archive.org/web/20101223043232/http://www.oceandots.com/indian/chagos/colvocoresses.php. Retrieved 2009-03-14.
- ↑ Personal experience from J. C. Hammack who had initially discovered the reef using the Landsat MSS images
- ↑ Personal experience from J. C. Hammack
| Atolls of the Chagos Islands; British Indian Ocean Territory |
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Atolls with land area: |