Attribute_Accuracy_Report:
The accuracy of the data is determined during data collection. The single-beam and interferometric swath bathymetry data were collected during concurrent research cruises in July, 2012. Methods are employed to maintain data collection consistency aboard various platforms. During mobilization, each piece of equipment, single-beam and swath, is isolated to obtain internal and external offset measurements with respect to the survey platform. All critical measurements are recorded manually and digitally and entered into their respective programs for calibration. Once calibration is complete and the calibration status is considered acceptable, survey operations commence. Each system has a dedicated computer, and efforts are made to use the same equipment and software versions on both systems. However, upgrades and changes can occur and require additional setup, measurements, and notation. For single-beam bathymetry, offsets between the single beam transducers and the Ashtech antenna reference point (ARP) were measured and accounted for in post-processing. Bar checks were performed as calibration efforts and accounted for any drift in the echosounder. Differential Geographic Positioning System (DGPS) coordinates were obtained using post-processing software packages (National Geodetic Survey On-Line Positioning User Service, OPUS, and Waypoint Product Group GrafNav, version 8.3). For the interferometric swath bathymetry, offsets between the sonar head and the DGPS antennas were measured and entered into the CodaOctopus F190R internal setup program. DGPS was provided through the OmniSTAR High Performance wide-area GPS service. DGPS is always implemented for navigational accuracy either during acquisition or as a post-processing step. These bathymetric data have not been independently verified for accuracy.
The single-beam and interferometric swath bathymetry data were collected during concurrent research cruises in July, 2012. Refer to the online data series linkage for field logs, vessel platform descriptions, and other survey information. This dataset was created to provide a single post-processed bathymetric grid from the merged datasets. The digital elevation model is 50-meter cell-size resolution; data gaps between acquisition tracklines are predicted values generated by the gridding algorithm.
This is a completely processed digital elevation model representing an interpolated bathymetric surface derived from the acoustic interferometric swath and single-beam bathymetry data.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
All static base station sessions were processed through the On-Line Positioning User Service (OPUS) maintained by the National Oceanic and Atmospheric Administration (NOAA) and the National Geodetic Survey (NGS). The base location results from OPUS were entered into a spreadsheet to compute a final, time-weighted positional coordinate-latitude, longitude, and ellipsoid height-. Base station positional error for each GPS session was calculated as the absolute value of the final position minus the session position value. The maximum horizontal error of the base station coordinates used for post-processing the single-beam bathymetry was 0.00042 seconds latitude and 0.00096 seconds longitude for TMRK and 0.00036 seconds latitude and 0.00047 seconds longitude for BERM. The stated horizontal accuracy of the OmniSTAR HP navigation subscription used during swath bathymetry acquisition is reported by the service as +/-15 centimeters (cm)(95 percent of the time).
Quantitative_Horizontal_Positional_Accuracy_Assessment:
Horizontal_Positional_Accuracy_Value: 0.00000 - 0.00042
Horizontal_Positional_Accuracy_Explanation: latitude decimal seconds
Quantitative_Horizontal_Positional_Accuracy_Assessment:
Horizontal_Positional_Accuracy_Value: 0.00000 - 0.00096
Horizontal_Positional_Accuracy_Explanation: longitude decimal seconds
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
All static base station sessions for TMRK and BERM were processed through the On-Line Positioning User Service (OPUS) maintained by the National Oceanic and Atmospheric Administration (NOAA) and the National Geodetic Survey (NGS). The base location results from OPUS were entered into a spreadsheet to compute a final, time-weighted positional coordinate-latitude, longitude, and ellipsoid height. Base station positional error for each GPS session was calculated as the absolute value of the final position minus the session position value. SPCMSC standards define the maximum acceptable vertical error for any individual base station GPS session as less than or equal to 3 times the standard deviation of the ellipsoid height; any occupations exceeding this error are removed and the base station coordinates are recalculated. For the TMRK base location the standard deviation of the ellipsoid height was 0.014 m, and the maximum difference from the average ellipsoid for any GPS session was +/- 0.030 m. For BERM base location the standard deviation of the ellipsoid height was 0.021 m and the maximum difference from the average ellipsoid for any GPS session was +/- 0.031 m. All the processed single-beam bathymetry data (x,y,z) for 2012 are referenced to these base station coordinates. The differentially corrected navigation files-base station GPS processed to boat GPS- were exported from GrafNav and then imported into CARIS HIPS and SIPS version 7.1, and then merged, by time, with the HYPACK (version 10.0.5.31) raw data files, at which point the soundings were geometrically corrected for motion and speed of sound. For the single-beam soundings, elevation differences at all trackline crossings were less than or equal to 0.14 m, and the elevation differences were within +/- 0.10 m for 89.28 percent of the 653 crossings. The stated vertical accuracy of the OmniSTAR HP navigation subscription used during swath bathymetry acquisition is +/-0.15 m (95 percent of the time). The Coda Octopus F190R IMU, which integrates the OmniSTAR HP position with motion, measures vessel velocity (+/- 0.014 meters/second (m/s)), roll and pitch (< 0.025 degrees), heading (1 m baseline 0.1 degrees), and heave (5 cm per meter (m) of depth). The vertical accuracy for the SWATHplus-H system varies with depth and across track range. At 57 m it is accurate to 10 cm vertically. Maximum vertical transformation error reported by VDatum is 0.171 m or 17.1 cm for eastern Louisiana. The sum of the errors (+/- 0.031 m plus +/-0.15 m plus 0.171 m) in the vertical is equal to +/-.352 m or +/- 35.2 cm.
Process_Step:
Process_Description:
GPS Acquisition: A GPS base station was erected at a temporarily installed USGS benchmark (TMRK) located on the sound side of the Chandeleur Islands. A second base station (BERM) was erected on the furthest northern island, providing differential GPS coverage for the survey area within a 15 kilometer (km) radius of either benchmark. GPS receivers recorded the 12-channel full-carrier- phase positioning signals (L1/L2) from satellites via the Thales choke-ring antenna at the base stations. This GPS instrument combination was duplicated on the single-beam survey vessel (rover). The base receiver and the rover receiver record their positions concurrently at 1-second (s) recording intervals throughout the survey.
Process_Date: 2012
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Nancy T. DeWitt
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 502-8000
Contact_Electronic_Mail_Address: ndewitt@usgs.gov
Process_Step:
Process_Description:
Single-Beam Bathymetry Acquisition: The single-beam bathymetric data were collected aboard the 22-foot RV TwinVee. Boat motion was recorded at 50-millisecond (ms) intervals with a Teledyne TSS Dynamic Motion Sensor (TSS DMS-05). HYPACK version 10.0.5.31, a marine surveying, positioning, and navigation software package, managed the planned-transect information and provided real-time navigation, steering, correction, data quality, and instrumentation-status information to the boat operator. Depth soundings were recorded at 50 ms intervals with a Knudsen 320BP echosounder system using a 200 kilohertz (kHz) transducer. Data from the GPS receiver, motion sensor, and fathometer were recorded in real-time and merged into a single raw data file (.raw) in HYPACK. Each device string was referenced by a device identification code and time stamped to UTC. Sound velocity measurements were collected using an Applied Microsystems Smart Sound Velocity Profiler (SVP). The instrument was cast overboard periodically, throughout the survey, to observe changes in water column speed of sound (SOS).
Process_Date: 2012
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Nancy T. DeWitt
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 502-8000
Contact_Electronic_Mail_Address: ndewitt@usgs.gov
Process_Step:
Process_Description:
Swath Bathymetry Acquisition: The interferometric swath bathymetry data were collected aboard the RV Survey Cat using a SEA SWATHplus-H 468 kHz interferometric sonar system mounted on a sled attached to a rail system, which was fastened between the catamaran halls. This allowed the instrument to align directly below the GPS antennae and minimize geometry errors. Boat position and motion data were recorded in real-time with a CodaOctopus F190R wetpod inertial measurement unit(IMU) mounted underwater between the transducer heads, to minimize lever arm geometry errors between the observed depths and associated vessel motion. Real-time corrected positions were acquired with an OmniSTAR HP (High-Precision differential global navigation satellite system) satellite constellation subscription. OmniSTAR HP position correction data and motion data from the IMU were integrated with interferometric soundings in the SWATHplus software package versions 3.7.17, with positional and calibration offsets pre-defined by a session file(.sxs), allowing for real-time- corrected depths. Prior to deployment, all equipment offsets were surveyed in dry dock with a laser total station. During the survey, all swath tracklines were recorded in SEA SWATHplus raw data format (.sxr). A Valeport Mini Sound Velocity Sensor (SVS) was attached to the transducer mount and collected continuous speed of sound (SOS) measurements at the depth of the transducers. These values were directly read and incorporated into the SWATHplus acquisition software, giving real-time speed of sound at the transducer while underway. In addition, a separate sound velocity profiler (Valeport miniSVP) was used to collect SOS profiles (water surface to seafloor) at intervals throughout the survey.
Process_Date: 2012
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Nancy T. DeWitt
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 502-8000
Contact_Electronic_Mail_Address: ndewitt@usgs.gov
Process_Step:
Process_Description:
Swath Bathymetry Processing: Position data recorded by the Coda-Octopus F190R IMU system were corrected in real time via the OmniSTAR HP differential navigation system. The IMU applied real-time motion corrections for heave, roll, and pitch to the vertical component of each position fix. The corrected positions were integrated with the observed bathymetric values to calculate a final ellipsoid height and position, representing the elevation of the seafloor with respect to the geodetic reference frame ITRF05 across the swath range. SWATHplus served as both an acquisition software and initial processing software. Preliminary roll calibration trackline data were collected and processed with Systems Engineering and Assessment Ltd SWATHplus and Grid Processor software version 3.7.17. Instrument offset and calibration values were entered into the session file (.sxs) and the raw data files (.sxr) were processed using the updated system configuration containing roll calibration values, measured equipment offsets, acquisition parameters, navigation and motion from the F190R, SOS at the sonar head, and SVP cast data. Any calibration offsets or acoustic filtering applied in SWATHplus was also written to the processed data file (.sxp). The initial real-time processing datum for the swath and backscatter data was ITRF05, which is the acquisition datum for OmniSTAR HP position and navigation data.
Processed data files were imported into CARIS HIPS and SIPS version 7.1, and original sounding data were edited for outliers using the program's depth filters and reference surfaces. Remaining outliers were deleted out manually. A CARIS Bathymetry with Associated Statistical Error (BASE) surface with associated Combined Uncertainty and Bathymetry Estimator(CUBE) sample surface was created from the edited soundings dataset. A BASE hypothesis is the estimated value of a grid node representing all soundings within a chosen resolution or grid-cell size (for example, 5 m) weighted by uncertainty and proximity, giving the final value as a "sample" of the data within the specific grid cell. This algorithm allows for multiple grid-node hypotheses to be verified or overridden by the user, while maximizing processing efficiency. A 5-m resolution CUBE surface was created to perform initial hypothesis editing using the CARIS Subset Editor tool, followed by higher resolution surface detail editing within the subset editor. The sample x,y,z data were exported as ASCII text at a 5-m by 5-m sample resolution in the ellipsoid datum of ITRF05.
Process_Date: 2013
Source_Produced_Citation_Abbreviation: 12BIM03_IFB_04_005_ITRF05.txt
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Nancy DeWitt
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 502-8000
Contact_Electronic_Mail_Address: ndewitt@usgs.gov
Process_Step:
Process_Description:
Differentially Corrected Navigation Processing: The coordinate values of the GPS base station (TMRK) are the time-weighted average of values obtained from the National Geodetic Survey's On-Line Positioning User Service (OPUS). The base station coordinates were imported into GrafNav version 8.1 (Waypoint Product Group) and the kinematic GPS data from the survey vessel were post-processed to the concurrent GPS session data at the base stations. During processing, steps were taken to ensure that trajectories between the base and the rover were clean, resulting in fixed positions. By analyzing the graphs, trajectory maps, and processing logs that GrafNav produces for each GPS session, GPS data from satellites flagged by the program as having poor health or satellite time segments that had cycle slips could be excluded, or the satellite elevation mask angle could be adjusted to improve the position solutions. The final differentially corrected precise DGPS positions were computed at 1-second (s) intervals for each rover GPS session and exported in ASCII text format to replace the uncorrected real-time rover positions recorded during acquisition. The GPS data were processed and exported in World Geodetic System of 1984 (WGS84) (G1150) geodetic datum.
Process_Date: 2013
Source_Produced_Citation_Abbreviation:
Post-processed differential navigation data for the rover (boat) in ASCII text format. 3 files-forward, reverse, and combined trajectories- are produced for each GPS session file.
Process_Step:
Process_Description:
Single-beam bathymetry processing: All data were processed with CARIS HIPS and SIPS (Hydrographic Information Processing System and Sonar Information Processing System) version 7.1. The raw HYPACK (version 10.0.5.31) data files were imported into CARIS; the differentially corrected navigation files were imported using the generic data parser tool within CARIS; and any SVP profile casts were entered and edited using the SVP editor within CARIS. The bathymetric data components-position, motion, depth, and SOS- were merged and geometrically corrected in CARIS to produce processed x,y,z data. Next the data were edited for outliers and further reviewed in the Subset Editor utility for crossing status, and questionable data points or areas. The geometrically corrected point data were then exported as an x,y,z ASCII text file referenced to WGS84(G1150), which is equivalent to ITRF00, and ellipsoid height in meters.
Source_Used_Citation_Abbreviation:
Post-processed differential navigation data and raw HYPACK bathymetric data in ASCII text format.
Process_Date: 20120601
Source_Produced_Citation_Abbreviation: 12BIM04_SBB_ITRF00_03_xxx.txt
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Nancy DeWitt
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 502-8000
Contact_Electronic_Mail_Address: ndewitt@usgs.gov
Process_Step:
Process_Description:
Datum transformation: Using the transformation software VDatum version 3.2, both the interferometric swath and single-beam bathymetric data were transformed horizontally from their data acquisition datums-swath, ITRF05; single-beam, ITRF00- to the North American Datum of 1983 (NAD83) reference frame and the orthometric vertical datum NAVD88 using the National Geodetic Survey (NGS) geoid model of 2009 (GEOID09).
Source_Used_Citation_Abbreviation: 12BIM03_IFB_04_005_ITRF05.txt
Source_Used_Citation_Abbreviation: 12BIM04_SBB_ITRF00_03_xxx.txt
Process_Date: 2013
Source_Produced_Citation_Abbreviation: 12BIM03_IFB_NAD83_NAVD88_GEOID09.txt
Source_Produced_Citation_Abbreviation: 12BIM04_SBB_NAD83_NAVD88_GEOID09.txt
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Nancy DeWitt
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 502-8000
Contact_Electronic_Mail_Address: ndewitt@usgs.gov
Process_Step:
Process_Description:
Gridding Bathymetric data: Using Esri ArcGIS version 10.1, the swath and the single-beam elevations were examined for spatial distribution and vertical agreement. After combining the point data (x,y,z), a triangulated irregular network (TIN) was generated. The TIN surface and elevation point- shapefile were used in conjunction to visually scan for any remaining discrepancies. Once all data were reviewed, a 50-m by 50-m cell resolution digital elevation model (DEM) was generated using the natural neighbor algorithm in ArcGIS software. A raster mask was created from the polygon survey extent with the ArcGIS "polygon to raster" conversion tool. The DEM was then clipped to the raster mask using the ArcGIS Spatial Analyst "extract by raster mask" tool. To help reduce uncertainty in the final DEM, the ArcGIS Spatial Analyst "neighborhood" low pass raster-data filter was applied.
Source_Used_Citation_Abbreviation: 12BIM03_IFB_NAD83_NAVD88_GEOID09.txt
Source_Used_Citation_Abbreviation: 12BIM04_SBB_NAD83_NAVD88_GEOID09.txt
Process_Date: 2013
Source_Produced_Citation_Abbreviation: Chandeleurs_2012_50_NAD83_NAVD88_GEOID09_DEM.tif
Process_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: U.S. Geological Survey
Contact_Person: Nancy DeWitt
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical
Address: 600 4th Street South
City: St. Petersburg
State_or_Province: FL
Postal_Code: 33701
Country: USA
Contact_Voice_Telephone: (727) 502-8000
Contact_Electronic_Mail_Address: ndewitt@usgs.gov
Process_Step:
Process_Description:
Added keywords section with USGS persistent identifier as theme keyword.
Process_Date: 20201013
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
