Rapid estimation of shallow seawater depth from airborne electromagnetics

MacNae, J, Robb, T and Vrbancich, J 2004, 'Rapid estimation of shallow seawater depth from airborne electromagnetics', Exploration Geophysics, vol. 35, pp. 288-291.


Document type: Journal Article
Collection: Journal Articles

Title Rapid estimation of shallow seawater depth from airborne electromagnetics
Author(s) MacNae, J
Robb, T
Vrbancich, J
Year 2004
Journal name Exploration Geophysics
Volume number 35
Start page 288
End page 291
Total pages 4
Publisher Australian Society of Exploration Geophysicists
Abstract Airborne electromagnetics (AEM) has been used on a test basis for determining water-depth (bathymetric sounding), with both fixed- and rotary-winged aircraft systems. Useful application is restricted to shallow water (up to a few tens of metres), and the systems can be used through sea-ice. Many processing methods to date, however, have involved extensive post-processing of data before bathymetric information can be extracted, with lag times of the order of months. We have investigated a number of methods for rapid bathymetric depth estimation that could be used in real time with AEM data acquisition. The fastest methods are all based on an initial rapid transform of data to conductance-depth sections. Once in conductance-depth space, it is possible to estimate depth from the maximum conductance encountered at each reading if the conductivity of seawater is known, and if the sea floor can be assumed electrically resistive. Alternatively, it is possible to attempt to solve for both seawater conductivity and depth independently using a thicklayer approximation, but this is a slower and potentially unstable process, but with the potential advantage that seafloor conductivity can be assessed. AEM and bathymetric sounding data have been used to appraise the validity of the approximate methods. These data included helicopter DIGHEM data collected over Sydney Harbour and fixed-wing GEOTEM data collected over and near Geographe Bay, Western Australia.
Subject Electrical and Electromagnetic Methods in Geophysics
Keyword(s) Bathymetry
airborne electromagnetics
DOI - identifier 10.1071/EG04288
ISSN 0812-3985
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