Archive of Side Scan Sonar and Swath Bathymetry Data Collected During USGS Cruise 10CCT01 Offshore of Cat Island, Gulf Islands National Seashore, Mississippi, March 2010

This is a GeoTIFF of the completed side scan sonar mosaic data product of Field Activity Number (FAN) 10CCT01.  For more information refer to the the  Data Series 563 that accompanies this file.

In March of 2010, the U.S. Geological Survey (USGS) conducted geophysical surveys east of Cat Island, Mississippi. The efforts was part of the USGS Gulf of Mexico Science Coordination partnership with the U. S. Army Corps of Engineers (USACE), to assist the Mississippi Coastal Improvements Program (MsCIP) and the Northern Gulf of Mexico Ecosystem Change and Hazards Susceptibility (NGOM) Project, by mapping the shallow geological stratigraphic framework of the Mississippi Barrier Island Complex. These geophysical surveys will provide the data necessary for scientists to define, interpret, and provide baseline bathymetry and seafloor habitat for this area, and to aid scientists in predicting future geomorpholocial changes of the islands with respect to climate change, storm impact, and SEA level rise. Furthermore, these data will provide information for barrier island restoration, particularly in Camille Cut and protection for the historical Fort Massachusetts. For more information refer to http://ngom.usgs.gov/gomsc/mscip/index.html.


This report serves as an archive of the processed swath bathymetry and side scan sonar data. Data products herein include gridded and interpolated surfaces, surface images, and x,y,z data products for both swath bathymetry and side scan sonar imagery. Additional files include trackline maps, navigation files, GIS  files, Field Activity Collection System (FACS) logs, and formal FGDC metadata. Scanned images of the handwritten FACS logs are also provided as PDF files. Refer to the Acronyms page for expansion of acronyms and abbreviations used in this report. 


The USGS Center for Coastal and Marine Science - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 10CCT01 tells us the data were collected in 2010 for the Coastal Change and Transport (CCT) study and the data were collected during the first field activity for that project in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. 

Data was collected using a twenty-six foot Glacier Bay Catamaran. Side scan sonar and interferometric swath bathymetry data were collected simultaneously along the tracklines. The side scan sonar towfish was towed off the port side just slightly behind the vessel close to the seafloor. The interferometric swath transducer was sled mounted on a rail attached between the catamaran hulls. During the survey the sled is secured into position. Navigation was acquired with a CodaOctopus F190 Precision Attitude and Positioning System and differentially corrected with OmniSTAR. See the digital FACS equipment log (13 KB) for details about the acquisition equipment used. Both raw data sets were stored digitally and processed using CARIS HIPS and SIPS software in the St. Petersburg office. For more information on processing refer to the Equipment and Processing page. Post-processing of the swath data set revealed a motion artifact which is attributed to movement of the pole that the transducers are attached to in relation to the boat. The survey was forced to take place in the winter months in which strong winds and rough waves contributed to a reduction in data quality. The rough seas contributed to both the movement of the pole and the very high noise base seen in the raw amplitude data of the side scan sonar. Compressed High Intensity Radar Pulse (CHIRP) data were also collected during this survey and are archived separately in Data Series 563 and can be downloaded at http://pubs.usgs.gov/ds/2010/563.

The ship was navigated using Differential Global Positioning System (DGPS) obtained using the CodaOctopus F190 Precision Attitude and Positioning System.  Two antennas received the integrated OmniSTAR differential correction. Unless noted all DGPS data is referenced to WGS84. The swath transducer sonar head was sled mounted between the catamaran pontoons. Offsets between the sonar head and the DGPS antennas were measured and entered into the F190 internal setup program.  The horizontal accuracy of bathymetric data is at the limit of OmniSTAR which is within 20 cm.

The towfish altitude varied considerably during the cruises due to the nature of shallow water surveying operations. Ideally SSS is flown at a relatively considerable distance from the vessel and other instruments to avoid acoustical interference. Some sources of acoustical interference are vessel vibrations and other instruments such as sub-bottom profilers and interferometric swath systems that utilize similar frequency ranges. However in shallow water surveying the optimal distance is difficult to achieve due to the negative buoyancy of the towfish and is also affected by unpredicted isolated shoals.