This bathymetric surface represents interpolated data at 2-meter resolution. Bathymetric data were processed to account for gaps that occurred along-track and between adjacent lines. Quality control and data processing were conducted to remove spurious points and minimize refraction artifacts. Soundings from the survey were processed and edited using Computer Aided Resource Information System (CARIS) Hydrographic Information Processing System (HIPS; versions 10.1 and 10.3). Although the soundings were edited, small data spikes may still exist. While much effort was devoted to cleaning the data and minimizing survey artifacts, some artifacts may still be seen in the final gridded bathymetric surface including an along track artifact at nadir (the ship track) and at the far edges of a survey line where adjacent swaths overlap. These artifacts are especially noticeable in areas of little local relief.
Nearly all survey line bathymetric data (generally surveyed parallel to the coastline) collected within the survey area were incorporated in this bathymetric surface.
Tielines and transit lines were typically excluded from this bathymetric surface, especially if equal or higher quality survey line data were available. Any tieline and transit line data would be used to verify tide corrections during post-processing. Data from the patch test lines were imported but not processed and are therefore excluded from this dataset.
Time gaps occur when no data were collected on 20160518, 20160521, and 20160522 (May 18 (JD 139), 21 (JD 142), and 22 (JD 143), 2016) due to weather conditions, rough seas and equipment maintenance and (or) failure.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
USGS Field Activity 2016-017-FA: Navigation for the SWATHplus-M system was acquired using the WGS 84 coordinate system with an Applanix POS MV Wavemaster (model 220, V5), which blends Global Navigation Satellite Systems (GNSS) with acceleration data from a Inertial Measurement Unit (IMU) and GPS azimuthal heading. The POS MV was configured with two AeroAntenna Technologies GPS antennas located at either end of a 2-m baseline, which was oriented fore and aft and mounted atop the rigid pole on which the SWATHplus-M transducers were mounted at the bow of the R/V Rafael. DGPS positions were obtained from the primary antenna located on the forward end of the baseline, and the positional offsets between the antenna and the navigational reference point (the POS MV IMU) were accounted for in the Applanix POSView (version 8.60) acquisition software. DGPS positions are horizontally accurate to 0.5-2 meters, but accuracy can increase to less than 10 cm after post-processing with Applanix POSPac (version 8.1).
Positional offsets were applied within the SWATHplus acquisition software (version 3.07.17.00) and stored within the SXR format data.
Note that post-processed horizontal navigation data from the Applanix POS MV were applied during the bathymetry processing in CARIS software at a later date; see process step 3.
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
USGS Field Activity 2016-017-FA: Vertical accuracy of the raw data based on system specifications may approximate 1% of water depth. In the Town Neck Beach survey area, 1% of the water depth (1-18 meters) translates to a vertical accuracy range of 1-18 centimeters. However, overall vertical accuracies on the order of 50 cm or better are assumed based on the following considerations: the Applanix POS MV Wavemaster, used to correct for vessel roll, pitch, heave, and yaw, has a theoretical vertical accuracy of a few mm; and tidal offsets were corrected using a NOAA-generated zone tidal model, which introduces some error into the depth measurements.
USGS field tests (unpublished) using submerged targets suggest that the vertical accuracy of the RTK-GPS tidal correction is better than 30cm. Refraction artifacts were minimized by acquiring a range of sound velocity profiles with a hand-casted AML Minos X SVPT (Applied Microsystems) sound velocimeter (for the duration of survey 2016-017-FA). Sound velocity data were entered into the SWATHplus acquisition software to model the sound velocity structure of the water column. Changes in ship draft due to water and fuel usage were not considered.
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: 20160517
Ending_Date: 20160523
Source_Currentness_Reference:
Ground condition of survey dates: 20160517-20160523. No geophysical data were collected on May 18 (JD 139), 21 (JD 142), and 22 (JD 143), 2016; see Completeness_Report for more information.
Source_Citation_Abbreviation: raw data
Source_Contribution:
USGS Field Activity 2016-017-FA: A 234-kHz Systems Engineering and Assessment Ltd. (SEA) SWATHplus-M (now Bathyswath) interferometric sonar was mounted on a rigid pole on the bow of the R/V Rafael. Data were acquired during May 2016.
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 SEABed 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 60-percent transmit power, a 34-cycle transmit pulse length, 4096 samples per channel, and a ping range of 46 meters.
Speed of Sound: Sound-velocity profiles were collected several times each survey day with a hand-casted AML Minos X SVPT (Applied Microsystems) sound velocimeter.
Tides: Tides were originally corrected during post-processing to Mean Sea Level using a NOAA-generated zone tidal model (stellwagen_tides.zdf) and the nearest NOAA-observed tide dataset (Boston_MSL_8443970_June2016.tid) that included all the survey dates. The final bathymetry surface was transformed to the NAVD88 reference surface using VDatum (version 3.9).
Process_Step:
Process_Description:
Processing Step 1. Raw to processed conversion for USGS field activity 2016-017-FA: 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). During the conversion process, sound velocity profiles were used to minimize potential refraction artifacts from fluctuations in the speed of sound within the water column. Various bathymetric filters were applied to eliminate sounding outliers. Predicted tidal information was merged into the processed file (SXP) during this conversion, however final tidal corrections were applied later in the processing flow. Bathymetric filtering typically included low amplitude (100%), range (0-4 m), box (3-50 m depth, 1.5-75 m horizontal), median (window size of 5), alongtrack 1 (depth difference of 5 m, window size of 5 m, and learn rate of 0.7), alongtrack 2 (depth difference of 1.5 m, window size of 1 m, and learn rate of 0.9), and mean filters (0.25 m). These represent the typical parameters used for the majority of the survey but slight adjustments were required for some areas. This process step and all subsequent process steps were performed by the same person - Seth Ackerman.
Process_Date: 2016
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:
Processing Step 2. CARIS preliminary processing for USGS field activity 2016-017-FA: A new CARIS HIPS project (ver. 10.1) was created for this field activity with projection information set to Universal Transverse Mercator (UTM) Zone 19N, WGS 84. Each SWATHplus processed file (SXP) was imported to the new CARIS project using the Import/Conversion Wizard. Delayed heave from raw POS MV files was used to update HIPS survey lines using the import auxiliary data function. Navigation was reviewed and edited as needed using the navigation editor tool. Data were merged selecting no tide and the delayed heave source. A 2-m resolution Swath Angle Weighted (SWATH) surface was created to incorporate survey lines as they were processed, and the SWATH surfaces were reviewed for inconsistencies and anomalies. Beam-to-beam slopes and across track angle filters were applied to the soundings line by line and then further edited manually as needed. The refraction editor was used to adjust sound speed values in areas where velocimeter data did not adequately correct depth profiles obviously influenced by local anomalies in speed of sound through the water column. Survey lines were remerged and the surface was recalculated to incorporate processing edits. Preliminary processing was done during the survey and additional processing was done post-survey with CARIS HIPS and SIPS version 10.1. This process step was done between 2016 and 2018.
Process_Date: 2018
Process_Step:
Process_Description:
Processing Step 3. Prepare and apply POS MV and Zone Tidal Model data for USGS field activity 2016-017-FA: Post-processed navigation and vessel attitude data from POSPac SBET files were used to update HIPS survey lines using the import auxiliary data function in CARIS (version 10.3). Navigation source was set to Applanix SBET, and navigation was re-reviewed and edited as needed using the Navigation Editor tool. Tide data referenced to Mean Sea Level (MSL) were applied using the NOAA Zone Tidal Model (stellwagen_tides.zdf) and observed tide data from the nearest tidal station (Boston_MSL_8443970_June2016.tid). All survey lines were remerged selecting the Zone Tidal Model tides and delayed heave sources.
Process_Date: 2018
Process_Step:
Process_Description:
Processing Step 4. Final CARIS bathymetry surface creation and export: A final 2-m resolution SWATH surface was created using the Swath Angle method with a maximum footprint of 5. Then, small "no data" holidays were filled using the "Fill Raster Holiday" tool and a 5x5 cell filter using data from a minimum of 5 neighboring cells. The CARIS SWATH surface was exported as a 2-m resolution ASCII file referenced to UTM Zone 19N, WGS 84 and MSL tidal heights.
Process_Date: 201810
Source_Produced_Citation_Abbreviation: 2m_SWATH_MSL_v1.asc
Process_Step:
Process_Description:
Processing Step 5. Transform surface to NAVD88: The NOAA's Vertical Datum Transformation tool (VDatum v. 3.9) was used to transform the CARIS bathymetry surface (MSL) to the North American Vertical Datum of 1988 (NAVD 88).
Process_Date: 201810
Source_Produced_Citation_Abbreviation: 2m_SWATH_MSL_v1_NAVD88.asc
Process_Step:
Process_Description:
Processing Step 6. Convert NAVD88 ASCII to GeoTIFF: Global Mapper (version 18) was used to convert the ASC surface created from the VDatum software to a 32-bit GeoTIFF image representing the final bathymetry surface referenced to the NAVD 88 heights.
Process_Date: 2018
Source_Produced_Citation_Abbreviation: 2016-017-FA_Bathymetry2m_NAVD88_GeoTIFF.tif
Process_Step:
Process_Description:
Processing Step 7. Sound velocity profile (SVP) data were bundled with this bathymetry dataset to archive the sonuds speed dataset. The SVP data can be found in a zip file (2016-017-FA_SVP.zip) that contains 13 SVP profiles in text format. Each SVP text file has a header line with the following format: SoundVelocity (file type), 1.00 (file format version number), cast number (XX), date/time of file creation ( YYYYMMDDhhmm), latitude (decimal degrees), longitude (decimal degrees), radii around the lat/long position for which the profile is valid (set to 1 meter), date of profile start ( YYYYMMDDhhmm), date of profile stop ( YYYYMMDDhhmm), source instrument of the profile (MVP P, where P stands for Probe), number of values in the profile. After the header line, there are 2 columns of data separated by a space. The first column is depth (in meters) and the second column is speed of sound (in meters per second).
Process_Date: 201906
Source_Produced_Citation_Abbreviation: 2016-017-FA_SVP.zip
Process_Step:
Process_Description:
Added keywords section with USGS persistent identifier as theme keyword.
Process_Date: 20200807
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
