Data Analysis of Airborne Electromagnetic Bathymetry.
NAVAL OCEAN RESEARCH AND DEVELOPMENT ACTIVITY NSTL STATION MS
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This report describes an experimental evaluation of the concept of airborne electromagnetic bathymetry. The airborne electromagnetic data that forms the basis of this project was acquired with the Mark VI INPUT system along a 17-mile flight path off Cape Breton Island, Nova Scotia. Water depth beneath the flight path ranged from 0 to more than 40 m. A special-purpose inversion algorithm was developed for automatically determining seawater depths from the digital tapes that contain the flight data. The algorithm has proven itself to be fast, efficient, and highly stable. Its efficiency is best demonstrated by the low computing costs, that on a CDC 7600 computer, amount to about 5 centsmile. Although the algorithm is based on a one-dimensional model of the water-rock interface, it was able to follow reasonably sharp sea-bottom topography. One of the main features of the algorithm is its relative insensitivity to aircraft altitude and normal variations in the survey equipment configuration. The average absolute error in the depth estimates derived from the electromagnetic data was about 2 m. As the discrepanices between the intepreted depths and the soundings shown on the coastal charts are not systematic, it is most likely that they are related to the presence of electrically conductive bottom sediments. It also appears that the value of 4 siemensmeter taken as the conductivity of sea water is essentially correct.
- Physical and Dynamic Oceanography
- Theoretical Mathematics