Quantitative Backscatter Measurements With a Long-Range Sidescan Sonar

N.C. Mitchell, M.L. Somers

Research output: Contribution to journalArticlepeer-review


It is shown that useful relative backscatter strengths can be calculated from GLORIA long-range side-scan sonar data using a simple acoustic model. The calculation was performed on GLORIA side-scan sonar data collected during 1987 in the southern Indian Ocean. GEOSECS hydrographic information was used to access the effects of refraction (ray bending and aspherical spreading signal losses). Sea Beam bathymetry was used to correct the effective insonified area and compute the grazing angle. A major difficulty in performing this calculation over the terrain chosen (mid-ocean ridge topography) was one of adjusting navigation so that small features in Sea Beam and GLORIA data matched. Preliminary results show a 10-dB falloff in backscatter strength with decreasing grazing angle (10°-40°) at 6.5 kHz over what must presumably be a rough surface (extruded basalts and breccias). On rugged topography such as at a mid-ocean ridge, it appears that acoustic shadowing produces much of the variation seen on GLORIA images.
Original languageUndefined
Pages (from-to)368-374
Number of pages7
JournalIEEE Journal of Oceanic Engineering
Issue number4
Publication statusPublished - Oct 1989

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