Attribute_Accuracy_Report:
Image pixel values contain gray-scale acoustic reflectivity values normalized to an 8-bit data range (0-255). Low-backscatter is represented by dark tones (low values) and high-backscatter is represented by bright tones (high values). The nodata value is 0. The accuracy of the grey scale values was not checked, but normalizing the values adjusts the image for better viewing.
This GeoTIFF represents interferometric backscatter imagery collected along main survey lines at 1-meter per pixel resolution. Sonar data were nominally collected at 30-meter trackline spacing to ensure nearly 100 percent coverage of the survey area. Gaps may occur along-track and between adjacent lines, especially where the ship had to maneuver to avoid obstacles during surveying. An internal review of the dataset pointed out that nadir was not fully removed from L115f1 during processing.
Nearly all quality main survey line backscatter data (generally parallel to the river banks) that were collected within the survey area of the Connecticut River were incorporated in this backscatter image. Backscatter from the patch test and line 1 (collected in Long Island Sound) and line 160 (collected in the marina at Old Saybrook) was not processed because they were not part of the study area and are therefore excluded from this image.
Noisy or poor quality data were not included in the products. Data from some survey lines may have been 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 products either. The following lines were not used in the backscatter imagery:
Backscatter from the patch test and line 1 (collected in Long Island Sound) and line 160 (collected in the marina at Old Saybrook) was not processed because they were not part of the study area and are therefore excluded from this image. Lines 118, 119, 133, 159 were gap fill lines that were collected fills reasonable sized holes in the bathymetry dataset. The backscatter coverage is typically greater than that of the bathymetry data using this system and processing method; in this dataset lines 118 and 119 had no backscatter gap; and the gaps near lines 133 and 159 were minimal; so none of these bathymetry gap fill lines were incorporated into the backscatter mosaic. The backscatter data in lines 115, 120, 121, 122, and 134 had relatively poor data quality and were not mosaicked so they would not interfere with decent quality data in adjacent lines.
Small cross-track gaps occur as a result of the ship pitching and rolling; between-track gaps occur where overlapping swaths were not achieved. These gaps were not filled or interpolated in the backscatter imagery.
Time gaps occurred during this field activity where no surveying was done due to bad weather, rough seas and stops in surveying for equipment issues. No sonar data were collected on Tuesday 20120918.
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: Unpublished Material
Title: raw SWATHplus-M data
Type_of_Source_Media: disc
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20120916
Ending_Date: 20120921
Source_Currentness_Reference:
ground condition during the survey dates: 20120916-20120921; see Completeness_Report for more information
Source_Citation_Abbreviation: raw data
Source_Contribution:
USGS Field Activity 2012-024-FA: A 234 kHz Systems Engineering and Assessment Ltd. (SEA) SWATHplus-M interferometric sonar was mounted on a rigid pole on the bow of the R/V Rafael. Data were acquired during September 2012.
Configuration:
Survey: Survey lines were run at an average speed of 5 knots and were generally spaced 30 m apart to obtain overlapping swaths of data and full riverbed coverage.
Sonar: The SEA SWATHplus-M operates at a frequency of 234 kHz and a variable range (increased or decreased manually depending on water depth). The system was operated with a transmit power: 60 percent, a transmit pulse length: 34 cycles, 4096 samples per channel, ping range of 46 meters. Additional sonar configuration information that are not necessarily applicable to the backscatter imagery can be found in the metadata for the bathymetry surface included with this data release (
https://doi.org/10.5066/F7PG1Q7V).
Process_Step:
Process_Description:
1. Each raw SWATHplus bathymetric sonar file (SXR) was converted to a SWATHplus processed file (SXP) using SEA SWATHplus Swath Processor (ver. 3.07.17.00). Conversion to SXP format retained all recorded data (Output Processed File/Processed Data Output Settings/Data Selection/Store All Data). This process step and all subsequent process steps were performed by the same person - Seth Ackerman.
Process_Date: 201209
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Seth Ackerman
Contact_Organization: U.S. Geological Survey
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
Address: 384 Woods Hole Rd.
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Country: USA
Contact_Voice_Telephone: 508-548-8700 x2315
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: sackerman@usgs.gov
Process_Step:
Process_Description:
2. SXPTools (version 20111004) software was used to process the backscatter data. An empirical gain normalization was applied to each SXP file to optimize the dynamic range of recorded backscatter intensity (SXPTools/SXPEGN). SXPMAGIC was used to interpolate backscatter intensity values across gaps at nadir that resulted from the filtering methods used to process the bathymetric soundings (SXPTools/SXPMAGIC).
Process_Date: 201210
Process_Step:
Process_Description:
3. Groupings of the SXPTools processed "filled" SXP files were mapped into several 1-meter resolution images using the SWATHplus GridProc software.
Process_Date: 201210
Process_Step:
Process_Description:
4. The individual backscatter images for lines 2-19, 20-40, 41-55, 56-84, 85-95, 96-113, 114-117, 123-132, 134-151, 152-157, and 158 were mosaicked together using PCI Geomatica - OrthoEngine (version 2013.0.2). No blend-effect was used therefore some sharp tonal differences may exist where subareas were mosaicked together. The final backscatter image was exported as 8-bit GeoTIFF images (UTM Zone 18N, WGS 84) at 1-m resolution. High backscatter intensity values are shown by light tones and low backscatter intensity values are shown by dark tones in the imagery.
Process_Date: 20130926
Source_Produced_Citation_Abbreviation: 2012-024-FA_Backscatter1m.tif
Process_Step:
Process_Description:
5. A world file with the same prefix file name and .tfw extension was created in ArcMap version 10.3.1 using EXPORT RASTER WORLD FILE tool.
Process_Date: 20170730
Source_Produced_Citation_Abbreviation: 2012-024-FA_Backscatter1m.tfw
Process_Step:
Process_Description:
Added keywords section with USGS persistent identifier as theme keyword.
Process_Date: 20200908
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: VeeAnn A. Cross
Contact_Position: Marine Geologist
Contact_Address:
Address_Type: Mailing and Physical
Address: 384 Woods Hole Road
City: Woods Hole
State_or_Province: MA
Postal_Code: 02543-1598
Contact_Voice_Telephone: 508-548-8700 x2251
Contact_Facsimile_Telephone: 508-457-2310
Contact_Electronic_Mail_Address: vatnipp@usgs.gov
