Multibeam echo sounder (MBES) data were collected during day-trip survey operations, usually 8-10 hours per day. Acquisition may have been suspended briefly during file changes or for longer periods during turns and system calibration, malfunction, or troubleshooting system issues. Any gaps between the polyline features in this shapefile reflect those time periods where data were not recorded.
Note that the M_ and S_ survey lines are collected simultaneously because of the dual-headed sonar system. The sonar files are often coincident, although occasionally becomes unsynchronized which does not affect the quality of the data, just the timing of survey file changes and line naming. Therefore, the total length of survey lines reported in this dataset will be approximately double the actual distance traveled by the survey vessel during data collection.
The only multibeam-sonar data collected on 20180531 (May 31, Julian day 151) was the sonar patch test, used to calibrate any attitude offsets for the bathymetry data; these data were processed and used for the patch test but not incorporated into the final bathymetry dataset since the same area was re-occupied on subsequent survey days. However, the patch test tracklines are included in this shapefile. Also, no data were collected on 20180603 (June 3; Julian day 154) due to rough sea-state.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Navigation data were 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 Motion Reference Unit (MRU) 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 MBES pole, approximately midships on the starboard side of vessel. 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).
Source_Information:
Source_Citation:
Citation_Information:
Originator: U.S. Geological Survey
Publication_Date: Unpublished Material
Title: raw MBES data in s7k format
Geospatial_Data_Presentation_Form: digital data
Type_of_Source_Media: disc
Source_Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 20180531
Ending_Date: 20180610
Source_Currentness_Reference: ground condition
Source_Citation_Abbreviation:
Reson T20P multibeam echo sounder raw bathymetry and backscatter
Source_Contribution:
Multibeam echo sounder (MBES) bathymetry and backscatter data were collected using dual-head Reson T20-P sonars. The pair of mills cross transmit and receive arrays were mounted side-by-side within a bracket that oriented them at opposing 30-degree angles (relative to horizontal). The bracket was pole-mounted on the starboard side of the R/V Petrel so that the sonar arrays were oriented athwart ships (primary and secondary arrays facing outward and down to port and starboard, respectively) and located approximately 1.235 m below the waterline when deployed. Vessel navigation and attitude data were acquired using an Applanix POS MV Wavemaster (model 220, V5) 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 MBES pole approximately midships on the starboard side of vessel, and the wetpod MRU mounted atop the sonar bracket just aft of the pole. An AML Micro X SV mounted on the sonar bracket monitored sound speed near the sonars during acquisition, and an ODIM MVP30 moving vessel profiler (MVP), mounted on the stern, was used to collect water column sound speed profiles at 1 to 2 hour intervals while underway (See shapefile 2018-001-FA_MVP_data.shp available from the larger work citation). The Reson SeaBat User Interface (version 5.0.0.6) was used to control the sonars, which were operated in intermediate mode at full power (220 db), with frequency-modulated pulses between 200 to 300 kHz. The range of the 1024 across track beams formed by the sonars were adjusted manually depending on water depth, and resulted in combined swath widths of 60 to 200 meters or typically 3 to 6 times the water depth. Data were monitored and recorded using the Reson SeaBat User Interface (UI) (version 5.0.0.6) and Hypack/Hysweep (version 2017, 17.1.3.0). The SeaBat User Interface logged the navigation, attitude, bathymetry, time-series backscatter, and water column data to s7k format files for each sonar. The line files were created by the Reson UI using the following naming convention: YYYYMMDD_HHMMSS_M/S. The line files were appended with a "M" and "S" suffix to denote the port (primary) "M" and "S" starboard (or secondary) sonar heads. HYSWEEP also was used to log the navigation, attitude, and bathymetry data for both sonars to a single HSX format file. The Reson SeaBat User Interface s7k data were used to produce the final processed backscatter mosaic and bathymetry grid.
Process_Step:
Process_Description:
PROCESSING STEP 1: CARIS HIPS DATA PROCESSING.
Multibeam bathymetry processing within CARIS HIPS (version 10.4.1) during the survey consisted of the following flow:
1) Vessel configuration files were created in CARIS for the port ("M"=main, or primary) and starboard ("S"=secondary) sonars (Petrel_dual_T20P_s7k_M.hvf, and Petrel_dual_T20P_s7k_S.hvf) which included relevant, linear and angular installation offsets for each T20-P unit as well as vendor specified uncertainty values for each of the survey sensors.
2) A CARIS HIPS project (version 10.4.1) was created with projection information set to Universal Transverse Mercator (UTM) Zone 18N, WGS 84. Separate HIPS projects were created for the Port (M), and Starboard (S) line files using the two vessel configuration files in #1 above.
3) Each Reson s7k file (M and S) were imported to the new CARIS projects (M and S respectively) using the Import/Conversion Wizard.
4) Delayed heave data from raw POS MV files were used to update HIPS survey lines using the import auxiliary data function.
5) Navigation was reviewed and edited as needed using the Navigation Editor tool.
6) Sound velocity correction was applied using the CARIS algorithm, a master SVP file containing all the sound velocity profiles collected during the survey and specifying the nearest in distance method, delayed heave source, and use surface sound speed.
7) Data were merged selecting no tide and the delayed heave source.
8) 4-m resolution Swath Angle Weighted (SWATH) surfaces were created to incorporate all the files (M and S) as they were processed, and the SWATH surfaces were reviewed for inconsistencies and anomalies.
9) The swath and subset editors were used to remove spurious points through manual editing and filter application, and the refraction editor was used to adjust sound speed values in areas where sound velocity data did not adequately correct depth profiles, which were obviously influenced by local anomalies in speed of sound through the water column.
10) Survey lines adjusted for refraction anomalies were remerged, and the respective SWATH surfaces were recomputed to reflect the changes. Processing during the survey was primarily focused on QA/QC during acquisition. Editing processes did require trial and error and were at times iterative. This process step was completed over the course of several months beginning with work done during the survey in June 2018; the date on this process step indicated below is the last day described processing was done. The contact person for this and all subsequent processing steps below is Seth Ackerman.
Process_Date: 201809
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: APPLY POST PROCESSED SBET FILES AND EDIT SOUNDINGS.
Post-survey processing within CARIS HIPS (version 10.4.1) consisted of the following flow:
1) Post-processed navigation, vessel attitude, and GPS height data from POSPac SBET files were used to update HIPS survey lines using the import auxiliary data function.
2) Navigation source was set to Applanix SBET, and navigation was reviewed and edited as needed using the Navigation Editor tool.
Process_Date: 201907
Process_Step:
Process_Description:
PROCESSING STEP 3: EXTRACT NAVIGATION.
Use Caris printfNav and Python to extract and reformat the navigation fixes stored in the Caris HIPS database and add them to a geospatial SQLite (version 3.27.1) database:
1) Extract navigation for each line in Caris HDCS directory using the Caris program printfNav for all the lines. (Extracted navigation file is tab-delimited in format YYYY-JD HH:MM:SS:FFF DD.LAT DD.LONG SSSSS_VVVVV_YYYY-JD_LLLL AR where YYYY=year, JD=Julian Day, HH=hour, MM=minute, SS=seconds, FFF=fractions of a second, DD.LAT=latitude in decimal degrees, DD.LONG=longitude in decimal degrees, SSSSS=survey name, VVVVV=vessel name, LLLL=linename, AR=accepted or rejected navigation fix). This step creates TXT navigation files for each survey line in the Caris project.
2) A Python script (CARIS_bathynav2sql_2018-001-FA.py) runs on the navigation TXT files, creating a new line in the SQLite database (which is created if it does not already exist) for each record, with new fields survey ID, vessel name, and system name. The script creates both point and polyline navigation for each survey line.
Process_Date: 202001
Process_Step:
Process_Description:
PROCESSING STEP 4: CREATE ESRI SHAPEFILE CONTAINING THE POLYLINE DATA:
The T20P polyline features was exported from the SQLite database as in ESRI Shapefile format using Spatialite-tools (version 4.3.0_3) using the terminal command:
> spatialite_tool -e -shp 2018-001-FA_T20P_Tracklines -d /Data/2018_001_FA_NJ/proc/SQLdb/2018-001-FA-SQLdb.sqlite -t BathyTrack_ln -g geom_bathyt -c CP1252 -s 4326 --type LINESTRING
Process_Step:
Process_Description:
PROCESING STEP 5: RENAME SHAPEFILE ATTRIBUTE TABLE FIELDS:
The trackline shapefile was loaded into an QGIS (version 3.10) project. The following attribute table field names were updated using the Layer Properties dialog: 'Year_JD_i0' was changed to 'YrJD_strt', 'JD_UTC_in0' was changed to 'JD_UTC_strt', 'Year_JD_e0' was changed to 'YrJD_end', and 'JD_UTC_end' was kept as is. The remaining field headers were unchanged. The QGIS tool Refactor was used to set the precision for the trackline length field.
Process_Date: 202004
