A Portable System For Ocean Bottom Imaging and Charting

Abstract

The Sea Mapping and Remote Characterization (Sea MARC) system is a sophisticated means of data acquisition in support of geophysical, acoustic, oceanographic, and hydrographic activities in all water depths. Typical real-time Sea MARC outputs can include ocean floor bathymetry, slant range corrected side-scan images, and sub-bottom profiles; these can be made at survey rates up to 10 square miles per hour. In addition to real-time displays, the Sea MARC data (along with ship's data and navigation information) are recorded on magnetic tape for later processing at on-shore computer facilities. Designed to be highly modular and flexible in configuration, the Sea MARC system comprises four primary sub-systems: an instrumented towfish, a telemetry and towing cable, a self-powered shipboard handling system and an on-deck data processing center. The system can be readily adapted to meet the data acquisition needs of a wide range of applications, from physical oceanography and marine geophysics to pipeline route surveys, drilling lease site investigations, and ocean mineral deposit characterization. During the past two years, while engaged by commercial, governmental, and academic agencies, one Sea MARC system has successfully imaged more than 10,000 square miles of ocean floor, including: the Mississippi and Laurentian fans, deepwater fracture zones, polymetallic sulfide deposits on the Juan de Fuca Ridge, and the continental margins of the U.S. and Canadian east coast. The use of a portable system for data acquisition as just described provides a cost effectiveness that cannot be matched by large, special purpose ships. As the outfitting and operating costs of these ships continues to escalate, systems such as the Sea MARC will perform an increasing portion of the offshore ocean survey activities that previously were the exclusive realm of large, dedicated oceanographic vessels.