Attribute_Accuracy_Report:
The accuracy of the data is determined during data collection. The SBB and IFB data were collected during concurrent research cruises in July and August of 2013. Methods were employed to maintain data collection consistency aboard various platforms. During mobilization, each piece of equipment (SBB and IFB) is isolated to obtain internal and external offset measurements with respect to the survey platform. Each system has a dedicated computer, and efforts are made to utilize the same equipment and software versions on both systems. However, upgrades and changes occur and require additional setup, measurements, and notation. DGPS was always implemented for navigational accuracy either during acquisition or as a post-processing step. These bathymetric data have not been independently verified for accuracy.
For the SBB, offsets between the single-beam transducers, the Ashtech antenna reference point (ARP), and the TSS motion unit were measured and accounted for on the rovers. For RTK in July (13BIM03 and 13BIm04) all respective base station parameters and rover parameters including antenna height and antenna models were entered into their respective GPS units. For the August surveys, all pertinent measurements were accounted for in the DGPS post-processing software packages (National Geodetic Survey On-Line Positioning User Service, OPUS, and Waypoint Product Group GrafNav, version 8.3). Bar checks were also performed as calibration efforts and accounted for any drift in the echosounder.
For the IFB, 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 Marinestar HP wide-area GPS service. All the critical measurements were recorded manually and digitally and entered into their respective programs for calibration. The CodaOctopus F190R was calibrated daily and survey operation would commence once calibration status was considered completed and acceptable.
The SBB and IFB data were collected during concurrent research cruises in July and August 2013. 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 DEM from the merged datasets. The DEM is 50-m cell-size resolution; data gaps between acquisition tracklines are predicted values generated by the gridding algorithm.
This is a completely processed DEM representing an interpolated bathymetric surface derived from the acoustic interferometric swath and single-beam bathymetry data.
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 (BRM2) was erected on the furthest northern island providing differential GPS coverage for the survey area within a 15 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 SBB data was acquired using RTK for 13BIM03 and 13BIM04 in July. Both base stations were equipped with a Magellan ProFlex500 GPS receiver, a Thales choke ring antenna, a Pacific Crest ADLP-1 390-430 megahertz (MHz) radio, and a Pacific Crest 5 decibel (dB) high power radio whip antenna. The radio whip antennas were placed onto 10-m collapsible masts providing line of site transmission to the vessels (rovers). The GPS and radio components were duplicated on each vessel. The base stations were set to record internally at a rate greater than or equal to the recording rate of the rovers, in this case 5 Hz. The known coordinates of each base station were entered into the GPS receiver and the RTK corrections were broadcast to the roving GPS receivers via the radio links at 5 Hz. The R/V Jabba Jaw recorded GPS positions at 1 Hz using an Ashtech Z-Xtreme GPS receiver and Thales choke ring antenna. The R/V Shark recorded GPS positions at a rate of 5 Hz using a Magellan ProFlex 800 GPS receiver and Ashtech marine antenna (table 2).
For the August SBB surveys (13BIM03) RTK was not used to collect SBB data and all navigation was post-processed to obtain DGPS. The base receivers and the rover receiver recorded their positions concurrently at 1-second (s) intervals throughout the survey. GPS data was acquired and processed in the World Geodetic Datum of 1984 (WGS84) (G1150).
Process_Date: 2013
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: Depth soundings were acquired aboard the R/V Jabba Jaw and the R/V Shark at 100-milliseconds (ms) using an Odom CV100 echosounder system with a 200 kilohertz (kHz) transducer. Boat motion was recorded on the R/V Jabba Jaw at 50-ms intervals using a Teledyne TSS Dynamic Motion Sensor (TSS DMS-05). The R/V Shark did not record boat motion. To minimize motion errors, the R/V Shark recorded GPS at a high rate (5 Hz) and utilized a short antenna height (lever-arm) in combination with a narrow (4 degree) transducer beam. All sensor data were saved into a single raw data file (.raw) in HYPACK, with each device string referenced by a device identification code and time stamped to Coordinated Universal Time (UTC). Sound velocity measurements were collected using a Valeport mini Sound Velocity Profiler (SVP) to observe changes in water column speed of sound (SOS).
Process_Date: 2013
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 IFB data were collected aboard the R/V Sallenger using a SEA SWATHplus-H 468 kHz interferometric sonar system. Boat position and motion were recorded in real-time using 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 via the use of the Marinestar HP satellite constellation subscription. Marinestar 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. 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 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 speed of sound profiles (water surface to seafloor) at intervals throughout the survey.
Prior to deployment, all equipment offsets between the sonar head and the DGPS antennas were surveyed in dry dock with the use of a laser total station. All the critical physical measurements between the DGPS antennas and the IMU were entered into the Coda F190R program for calibration. The CodaOctopus F190R was calibrated daily and survey operation would commence once calibration status was considered completed and acceptable. All critical physical measurements between the transducers and the IMU were entered into the SWATHplus configuration file (.sxs) for IFB acquisition.
Process_Date: 2013
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 Marinestar HP DGPS. The IMU also applied real-time motion corrections for heave, roll, and pitch to the vertical component of each position fix. The corrected positions were then 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 ITRF08 across the swath range. SWATHplus serves as both an acquisition software and initial processing software. Preliminary roll calibration trackline data were collected and processed using Systems Engineering and Assessment Ltd. SWATHplus and Grid Processor software version 3.7.17. Instrument offset and calibrations values were input into the session file (.sxs) and the raw data files (.sxr) were then 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 is also written to the processed data file (.sxp).
All processed data files were imported into CARIS HIPS and SIPS version 8.1.7, and the original sounding data were edited for outliers using the program's depth filters and reference surfaces. Any remaining outliers were then edited out manually. A CARIS BASE (Bathymetry with Associated Statistical Error) surface with associated CUBE (Combined Uncertainty and Bathymetry Estimator) sample surface was created from the edited soundings dataset. A BASE hypothesis is the estimated value of a grid node representing all the 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 subset editor. The sample x,y,z data were exported as ASCII text at a 5 x 5-m sample resolution in the ellipsoid datum of ITRF08.
Process_Date: 2013
Source_Produced_Citation_Abbreviation: 13BIM02_07_IFB_LEVEL_05_XXX_ITRF08.txt
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:
Differentially Corrected Navigation Processing: The coordinate values for each of the GPS base stations (TMRK and BRM2) are the time-weighted average of values obtained from the National Geodetic Survey's (NGS) On-Line Positioning User Service (OPUS). Depending on the survey design, the coordinates were utilized either during acquisition to provide RTK navigation, or imported into the post-processing software GrafNav (Waypoint Product Group). For post processing, the kinematic GPS data from the survey vessels were processed to the concurrent GPS data from the base stations. Steps were taken to ensure that the trajectories between the base and rover were clean and resulted in fixed positions. GPS data quality could be monitored and manipulated by analyzing the graphs, trajectory maps, and processing logs that GrafNav produces for each GPS session. If poor GPS data was identified, some common tools used to improve the solution included, but were not limited to, omitting a satellite flagged as poor in health, excluding time-segments with cycle slips, or adjusting the satellite elevation mask angle. The final, differentially-corrected, precise DGPS positions were computed at 1-second (s) intervals for each roving GPS session, and then exported in American Standard Code for Information Interchange (ASCII) text format, which replaced the uncorrected real-time rover positions recorded during acquisition. The GPS data were processed and exported in the World Geodetic System of 1984 (WGS84) (G1150) geodetic datum.
For USGS cruises 13BIM03 and 13BIM04, RTK navigation was implemented. The OPUS derived base station coordinates were programed into their respective base station GPS receivers and position corrections were broadcasted via radio link to the roving GPS receivers located on each survey vessel. However, 13BIM04 was ultimately post-processed using GrafNav version 8.50 after identification of some unreliable navigation segments. RTK was not implemented during cruise 13BIM08 so navigation data was post-processed using GrafNav version 8.4 and all pertinent base information details were accounted during processing.
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 using CARIS HIPS and SIPS (Hydrographic Information Processing System and Sonar Information Processing System) version 8.1.5. The raw HYPACK (version 10) 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 then merged and geometrically corrected in CARIS to produce processed x,y,z data. Next, the data were edited for outliers and then 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), equivalent to ITRF00, and ellipsoid height in meters.
Source_Used_Citation_Abbreviation:
Post-processed differential navigation data files and HYPACK RAW bathymetric data in ASCII text format.
Process_Date: 2013
Source_Produced_Citation_Abbreviation:
13BIM03_SBB_ITRF00_xyz.zip
13BIM04_SBB_ITRF00_xyz.zip
13BIM08_SBB_ITRF00_xyz.zip
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:
Datum transformation: Using the transformation software VDatum version 3.3, both the IFB and SBB data were transformed horizontally from their acquisition datums (IBF, ITRF08; SBB, 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:
13BIM02_07_ITRF08_xyz.txt
13BIM03_SBB_ITRF00_xyz.txt
13BIM04_SBB_ITRF00_xyz.txt
13BIM08_SBB_ITRF00_xyz.txt
Process_Date: 2013
Source_Produced_Citation_Abbreviation:
13BIM02_07_NAD83_NAVD88_GEOID09_xyz.txt
13BIM03_SBB_NAD83_NAVD88_GEOID09_xyz.txt
13BIM04_SBB_NAD83_NAVD88_GEOID09_xyz.txt
13BIM08_SBB_NAD83_NAVD88_GEOID09_xyz.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 10.3.1, 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 x 50-m cell resolution DEM was generated using the natural neighbor algorithm in ArcGIS software. A raster mask was created from the polygon survey extent using 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:
13BIM02_07_NAD83_NAVD88_GEOID09_xyz.txt
13BIM03_SBB_NAD83_NAVD88_GEOID09_xyz.txt
13BIM04_SBB_NAD83_NAVD88_GEOID09_xyz.txt
13BIM08_SBB_NAD83_NAVD88_GEOID09_xyz.txt
Process_Date: 2013
Source_Produced_Citation_Abbreviation: Chandeleurs_2013_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
