GLORIA

The original data were collected as part of the USGS EEZ-SCAN program, which was a cooperative mapping program between the US Geological Survey and the Institute of Oceanographic Sciences of the UK. The survey areas included the entire US EEZ of East Coast, Gulf of Mexico, Puerto Rico, West Coast, Bering Sea, Aleutian Islands, Gulf of Alaska, Hawaiian Ridge, and the US Virgin Islands of Johnston Island, Kingman Reef and Palmyra Atoll. The GLORIA system is a long-range sidescan sonar system developed at the Institute of Oceanographic Sciences of the United Kingdom. The system was specifically designed to map the morphology and texture of seafloor features in the deep ocean. Acoustic images of the seafloor are formed by transmitting sound pulses at the seafloor to either side of the towed vehicle and recording the backscattered sound waves. Two arrays of transducers mounted back to back are inside the towed vehicle. The arrays can emit pulses of energy at 20-, 30-, or 40-s intervals and, between transmissions, record the echoes from as far away as 30 km. The acoustic data are sequentially obtained from narrow strips of seafloor, and thus successive transmissions over adjacent strips of seafloor are used to construct an image line-by-line. The maximum swath width largely depends on the prevailing acoustic-propagation conditions. For GLORIA, the swath width can be as great as 30 km on each side of the track. Under normal conditions, however, it is usually somewhat less. If acoustic conditions are unfavorable and the water depth is less than about 1,500 m, then the range may be less than 10 km. The maximum range for the surveys is 22.5 km to either side of the ship's track.

* move your cursor over each island to see details of data distribution.