Georeferenced TIFF image displaying 1 meter resolution backscatter data collected by the U.S. Geological Survey in the Madison Swanson Marine Protected Area, Gulf of Mexico in 2000 (UTM Zone 16N, WGS 84, GeoTIFF image)

The SIS 1000 towfish by Datasonics was used to collect all of the sidescan-sonar data at a 400 meter total swath width. The data were recorded using ISIS by Triton Elics International in QMIPS format.

XSonar processing software (Danforth and others, 1991) was used to process the sidescan sonar QMIPS files. The files were demultiplexed using a 4x3 sample interval and a normalization value of 8192. The scan size was 768 pixels, and the output resolution was 0.781250 meters. A command-line script was used to help remove surface noise. An example of the command line is: removeSurface -S20 -p10 -s10 -N10 -O0.6 -i l35f1. -o l35f1new. Manual bottom tracking was used in order to remove the water column from the swaths with the slant range correction. Destriping and beam angle corrections were applied using 300 lines with a 100 ping overlap; maximum beam angle of 90; response angle = 55; data normalization = 0; port/starboard tone adjust = ON. This processing effectively aids in suppressing speckle noise and reducing file size, and corrects for slant-range distortion, signal attenuation, and dropped sonar pings. This process step and all subsequent process steps were performed by VeeAnn A. Cross.

Danforth, W. W., T. F. O'Brien, and W. C. Schwab. 1991. US Geological Survey Image Processing System: Near Real-Time Mosaicking of High-Resolution Sidescan-Sonar Data. Sea Technology, Jan. 1991: 54-59.

Danforth, W., 1997, Xsonar/ShowImage; a complete system for rapid sidescan sonar processing and display: U.S. Geological Survey Open-File Report 97-686, 77 p.

The individual lines were then processed with the WHIPS software package to additionally filter the lines using a 7 line filter starting with L19F1 and mapping the odd and even lines into separate georeferenced images for mosaicking in PCI software (Paskevich 1992; Paskevich 1996). These images had a pixel resolution of 1 meter/pixel.

Paskevich, V. F. 1992. Digital Mapping of Sidescan Sonar Data with the Woods Hole Image Processing System Software. Open-File Report 92-536, 87 pp.

Paskevich, V. F. 1996. MAPIT: An Improved Method for Mapping Digital Sidescan Sonar Data using the Woods Hole Image Processing System (WHIPS) Software. Open-File Report 96-281, 73 pp.

Non-overlapping swaths were then brought into the remote sensing software package PCI Geomatics. Two channels were used so that one channel (line by line) could be brought in and mapped - mosaicked - to the other channel by picking control points to further constrain the positioning of the line. The lines set as "true" were the odd lines, and the even lines were mapped to those using control points. The final mosaic was then exported from PCI as a TIFF image with an associated world file for georeferencing purposes. GeoTiffExamine was then used to add the world file information to the TIFF image transforming it into a GeoTIFF.

The online links to the data were updated to reflect the new server hosting the data. Additionally, other small edits could be made to the metadata, such as modifying http to https where appropriate. The metadata date (but not the metadata creator) was edited to reflect the date of these changes.

Added keywords section with USGS persistent identifier as theme keyword.