Survey lines along which swath backscatter data were collected south of Martha's Vineyard and north of Nantucket by the U.S. Geological Survey offshore of Massachusetts in 2013 (2013-003-FA_BackscatterTracklines, Esri Polyline Shapefile, Geographic, WGS84)

This dataset includes all of the swath-backscatter trackline navigation that was processed for USGS field activity 2013-003-FA. On a case by case basis, some of the swath-backscatter data may not have been processed and therefore no trackline was created (e.g. if a line was stopped for various reasons and a new line was restarted covering the same area of the original survey line or if a line was split during processing and a section of the line was not used or processed). Line L1f1 was split due to navigation errors and issues with staying on the survey line. The line was restarted as L1f2, and the split off section at the end of line L1f1 was discarded. Line L59f1 was split so that data collected after the end of the line, during a turn and transit to the next survey line, could be discarded. L43f1 was split into L43f1-CH12 and L43f1-CH12-SPL000, and both were processed and included in the backscatter mosaic. Line L212f1 was split where the vessel veered offline to collect a sound speed cast, and the split off section was discarded. This shapefile includes trackline navigation from all processed swath-backscatter data; only quality sonar data along the main survey lines were included in the final backscatter mosaic (2013-003-FA_Backscatter1m.tif) found in this report. Excessively noisy or poor quality data were not included in the final mosaic. Data from some survey lines were omitted where they overlapped with equal or better quality data from adjacent lines. Data along tie and transit lines were generally not included in the final mosaic either. An approximately 24 square kilometer area offshore of Edgartown Great Pond (south of Martha's Vineyard, MA) was not surveyed because it was surveyed in 2007 using the same system as part of a separate project to study the area around Woods Hole Oceanographic Institution (WHOI) Martha's Vineyard Coastal Observatory (MVCO), see USGS Open File Report 2008-1288 for more information http://pubs.usgs.gov/of/2008/1288/. The only data from the SWATHplus system processed and published from the 2007 survey was the swath bathymetry; backscatter data from 2007 survey was from a Klein 3000 dual-frequency sidescan-sonar (L3-Klein Associates). Time gaps occurred during this field activity where no surveying was done due to bad weather, rough seas and stops in port for crew changes. Planned surveying was paused and no main survey line data were collected during these times:

JD143 15:20 - JD146 20:06 (no data were collected on JD144 or JD145)
JD149 15:40 - JD151 18:59 (no data were collected on JD150)
JD153 00:01 - JD153 14:32
JD155 18:16 - JD156 02:06
JD158 06:12 - JD160 19:15 (no data were collected on JD159)