Acoustic-backscatter data from repeat side-scan sonar surveys of south San Francisco Bay, California, 2023-2025

Surveys were conducted on October 25-26, 2023, January 8-9, 2024, January 23-25, 2024, March 6-8, 2024, October 15-16, 2024, January 14-15, 2025. All six surveys were conducted using the same mapping systems and post-processed using the same methodology. The data were collected with a SWATHplus-M 234-kHz interferometric side-scan sonar system pole-mounted on the U.S. Geological Survey (USGS) R/V Parke Snavely. During the mapping mission, an Applanix POS-MV (Position and Orientation System for Marine Vessels) was used to position the vessel during data collection, and it also accounted for vessel motion such as heave, pitch, and roll. The POS-MV also recorded position and vessel motion parameters for later post-processing. Sound-velocity profiles were collected throughout the survey days with a Castaway CTD. Post-processed POS-MV Smoothed Best Estimate of Trajectory (SBET) files were merged with the survey line files using BathySwath software and then the line files were imported into SonarWiz software. Acoustic-backscatter data were processed using SonarWiz software techniques and gridded into 1-m resolution images. The images were exported as Erdas Imagine files in UTM zone 10, WGS-84 coordinates and imported into a GIS (ArcGIS Pro). The images were then projected to UTM zone 10, NAD83(2011) coordinates using ArcTools raster projection tool. The images were exported as a GeoTIFF file in UTM zone 10, NAD83(2011) coordinates.