Sidescan sonar polyline shapefile of trackline navigation files collected by the U.S. Geological Survey in the Madison Swanson and Steamboat Lumps Marine Protected Areas, Gulf of Mexico in 2000 (Geographic, WGS 84)

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. One result of the demultiplexing of the QMIPS file is the output navigation file with fixes approximately every 2 minutes.

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.

The individual survey areas are grouped into folders - Control, MadSwan, Steam, and Transit. A PYTHON script was written to access each folder and process the individual files to convert them to comma-delimited text files with the navigation as decimal degrees. A second PYTHON script was written to take this text file and convert it to a shapefile outside of ArcGIS using the shapefile.py class file.

ArcMap 9.3.1, ArcToolbox (Data Management Tools - Projections and Transformations - Define Projection) tool was used to define the projection as Geographic, WGS 84.

In ArcMap 9.3.1, VACXtras (v 3.1.2) Point to Line v2 was used to convert the navigation point shapefile to a polyline shapefile with the LineID as the line delimiter. VACXtras is a collection of Visual Basic tools used in the Woods Hole Coastal and Marine Science Center written by VeeAnn A. Cross. The tool enables the user to store attributes from the input point shapefile into the output polyline shapefile. In this case, for the start of the line, the Lat, Long, JDTime, Year, and Survey attribute values were carried over. For the end of the line, the Lat, Long, and JDTime attributes were carried over (as Lat_end, Long_end, and JDTime_end). An automatically generated attribute, Id, which serves no usable function in this case - was deleted from the shapefile.

Filename was changed to more precisely reflect the field activity number.

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.