Abstract:

These data are high-resolution acoustic backscatter measurements of the seafloor offshore of Massachusetts, from Nahant to Gloucester. Approximately 127 km² of the inner shelf were mapped in the nearshore region between the 10m and 40-m isobath.

Purpose:

These data were collected under a cooperative agreement with the Massachusetts Office of Coastal Zone Management (CZM) and the U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Science Center. High resolution bathymetry, backscatter intensity, and seismic profile data were collected over 127 km² area covering a portion of the South Essex Ocean Sanctuary to characterize the surface and subsurface of the seafloor for regional geologic framework investigations.



Backscatter data were collected during two different surveys. Survey RAFA03007 

began Monday, 22 Sep 2003 (JD267) and ended on Tuesday, 14 Oct 2003 (JD287). RAFA04002 began 17 Apr 2004 (JD 108) and ended on 2 May 2004 (JD123).

Currentness reference:

ground condition

Use constraints:

Data are not intended for navigational use.



These data should not be used at resolutions for which it is not intended.



Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.

Address:

384 Woods Hole Rd.

Logical consistency report:

These data have not been quantitatively compared to previous hydrographic data, although they generally agree with qualitative comparison of published NOAA charts.

Vertical positional accuracy report:

The RTK corrected signal was sent from a USGS survey-specific base station at the lighthouse on Eastern Point Lighthouse. The base station occupied a DMA monument, however, the x, & y positions were calculated for that location using a 3 day average of 12 hour data sets using the Online Positioning User Service (OPUS, National Geodetic Survey) solution. Sidescan tow fish layback was 6 meters.

Process description:

Sidescan data were acquired with Edgetech DF-1000, dual frequency towed sidescan sonar with average layback of

Collected with 150m range layback = 6 meters

Process description:

raw .xtf data were processed and corrected for slant range corrections in XSONAR/SHOWIMAGE

Process description:

the Xsonar files were mosaiced in Xsonar and then exported to PCI Geomatica as raw files

Process description:

PCI Geomatica mosaiced individual line files and georeferenced to UTM Z 19

Process description:

The positional accuracy of the final 1m resolution mosaic was increased by further georeferrencing (rubber sheeting) to the submetrix interferometric sonar backscatter mosaic. The interferometric data has higher order positional accuracy than the towed sidescan-sonar because the GPS antenna is mounted on top of the same pole as the interferometric sonar and there is no inacuracies from towfish layback. The rubber sheeting was calculated in ArcGIS with the Georefferencing.

*Attribute definition:

Internal feature number.

*Attribute definition source:

ESRI

Dataset overview:

Sidescan sonar mosaic in ESRI georeferenced tif format. Data values represent relative acoustic backscatter from 100kHz towed sidescan sonar.

Address:

384 Woods Hole Rd.

Distribution liability:

Although this data set has been used by the U.S. Geological Survey (USGS), no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials.



Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Format specification:

Georeferenced Tiff

Address:

384 Woods Hole Rd.

ss_mos1m.tif- Nahant to Gloucester, 1m resolution Sidescan Sonar Mosaic
	Data format: Raster Dataset - TIFF File or table name: ss_mos1m.tif Coordinate system: Universal Transverse Mercator Theme keywords: U.S. Geological Survey, USGS, Coastal and Marine Geology Program, CMGP, Woods Hole Science Center, WHSC, Seafloor, Marine Geology, ArcGIS Raster, field activity serial number RAFA03007, field activity serial number RAFA04002, Sidescan, Sidescan Sonar, Edgetech, DF-1000, oceans and estuaries, elevation, imageryBaseMapsEarthCover
Abstract: These data are high-resolution acoustic backscatter measurements of the seafloor offshore of Massachusetts, from Nahant to Gloucester. Approximately 127 km² of the inner shelf were mapped in the nearshore region between the 10m and 40-m isobath.

FGDC and ESRI Metadata: