ABSTRACT: Comparison of GLORIA and SeaMARC I Side-Scan Sonar Images on the Lower Mississippi Fan, Eastern Gulf of Mexico

David C. Twichell, S. O'Connell

Sidescan-sonar images collected by the low-frequency (6.5 kHz) GLORIA and higher frequency (30-kHz) SeaMARC I systems are compared to determine the similarity of features imaged by these two systems. The two data sets were digitally scaled to a 25-m pixel size and were registered relative to each other.

Images on the lower Mississippi fan show a small channel (<250 m wide) crossing a sea floor that exhibits varied acoustic backscatter textures and strengths. While the SeaMARC data show details not resolved by GLORIA, the regional backscatter patterns are remarkably similar on the two systems. The small channel, which has less than 5 m relief, is traceable by both systems. On SeaMARC, the channel is shown as having a low-backscatter floor and high-backscatter levees. Where the channel is more than 250 m wide, GLORIA shows the same pattern: where the channel is narrower, GLORIA merely shows a high-backscatter stripe from the more strongly reflecting broader levees. On the basis of this comparison, the minimum-size feature that GLORIA can resolve is about 250 m. The similarity of fea ures imaged by the two systems allows us to identify small features on GLORIA that then can be studied in greater detail using midrange side-scan sonar systems.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990