Open-File Report 01-448 Refraction Issues

Cruise Report; RV Moana Wave cruise M1-01-GM; the bathymetry and acoustic backscatter of the mid shelf to upper slope off Panama City, Florida, northeastern Gulf of Mexico; September 3, through October 12, 2001, Panama City, FL to Panama City, FL

Refraction Issues

The single biggest limitation on the quality of sounding data is water-column refraction. Refraction-related anomalies grow non-linearly with beam angle and the resulting artifacts can create short-wavelength topographic features that may be misinterpreted as seabed relief. There was some fear prior to the cruise that suspected strong water stratification would present a problem for the beam steering and ray tracing of individual beams. Although a strong thermocline was measured, repeated CTD casts allowed us to correct for refraction effects. A representative water-velocity profile is shown in Figure 7, 22kb. In additional, minor empirical refraction corrections were applied during processing. If all of the alignments are correctly determined, Kongsberg Simrad states that the depth resolution of the EM1002 is 30 cm or 0.1% of water depth, whichever is larger.

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Suggested citation:

Gardner, James V., Mayer, Larry A., Hughes Clarke, John E., Dartnell, Peter, Sulak, Kenneth J., 2001, Cruise Report; RV Moana Wave cruise M1-01-GM; the bathymetry and acoustic backscatter of the mid shelf to upper slope off Panama City, Florida, northeastern Gulf of Mexico; September 3, through October 12, 2001, Panama City, FL to Panama City, FL: U.S. Geological Survey Open-File Report 01-448, https://pubs.usgs.gov/of/2001/0448/.

U.S. Department of the Interior
SALLY JEWELL, Secretary

U.S. Geological Survey
Suzette M. Kimball, Acting Director