Attribute_Accuracy_Report:
The accuracy of the data is determined during data collection. The SBB data were collected during one research effort in August, 2015, USGS FAN 2015-326-FA. This dataset that utilized four vessels and is therefore internally consistent per platform. Methods were employed to maintain data collection consistency aboard the platform. During mobilization, each piece of equipment 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 all systems. However, upgrades and changes occur and require additional setup, measurements, and notation. DGPS was always implemented for navigational accuracy in post-processing. 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 roving vessels. 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 8.6). Bar checks were also performed as calibration efforts and accounted for any drift in the echosounder.
This file represents the post-processed bathymetric data (x,y,z) collected during SBB surveys. They represent data coverage for the single-beam portion the 2015 nearshore Dauphin Island, Alabama survey, specifically FAN 2015-326-FA (SubFans 15BIM10, 15BIM11, 15BIM12, and 15BIM13). Refer to the online data release linkage for field logs, vessel platform descriptions, and other survey information; this information is directly available at
https://doi.org/10.5066/F7BZ648W
These are complete post-processed xyz bathymetric data points from acoustic single-beam data collected in August 2015 from the nearshore areas of Dauphin Island, Alabama.
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
All static GPS base station sessions were run 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 one final coordinate and error analysis for that base location. Using the OPUS values for each day, and the total time that data were collected each day, the average daily weighted value of occupation time was calculated; longer occupation times held more value than shorter times. The final value for latitude, longitude, and ellipsoid was the weighted average of all the GPS session processed with OPUS. This value was entered in GrafNav version 8.6 as the base station coordinates. Error was calculated using output from OPUS for each day and was calculated as the absolute value of the final value minus the daily value. The maximum horizontal error of the base station coordinates used for post-processing the single-beam bathymetry was 0.00028 decimal seconds latitude and 0.00022 decimal seconds longitude for BH17 and 0.00027 decimal seconds latitude and 0.00018 decimal seconds longitude for WDAU.
Quantitative_Horizontal_Positional_Accuracy_Assessment:
Horizontal_Positional_Accuracy_Value: 0.00028
Horizontal_Positional_Accuracy_Explanation:
The maximum error for base stations BH17 and WDAU in latitude decimal seconds
Quantitative_Horizontal_Positional_Accuracy_Assessment:
Horizontal_Positional_Accuracy_Value: 0.00022
Horizontal_Positional_Accuracy_Explanation:
The maximum error for base stations BH17 and WDAU in longitude decimal seconds
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
All static base station sessions for BH17 and WDAU were processed through 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 three times the standard deviation of the ellipsoid height; any occupations exceeding this error are removed and the base station coordinates are recalculated. For BH17 base location, the standard deviation of the ellipsoid height was 0.005 m and the maximum difference from the average ellipsoid for any GPS session was +/- 0.015 m. For WDAU base location, the standard deviation of the ellipsoid height was 0.005 m and the maximum difference from the average ellipsoid for any GPS session was +/- 0.014 m.
Process_Step:
Process_Description:
GPS Acquisition: Two GPS base stations were erected on Dauphin Island. One base station was erected upon the National Geodetic Survey (NGS) Permanent Identifier (PID) BH1755.txt at the entrance to Fort Gaines on the eastern end of the island. The second GPS base station was erected at a temporarily installed USGS benchmark (WDAU) located on the western end of Dauphin Island just outside of the Dauphin Island Beach Parking lot. The strategically placed base stations then provided differential GPS coverage for the survey area within a 15 kilometer (km) radius of either benchmark. Each base was equipped with an Ashtech ProFlex GPS receiver which recorded the 12-channel full-carrier-phase positioning signals (L1/L2) from satellites via the Thales choke-ring antenna at a rate of 10 times per second.
The Ashtech ProFlex GPS instrument combination was duplicated on each single-beam survey vessels (rover). For the R/V Sallenger (15BIM10)and the R/V Jabba Jaw (15BIM11) the receivers were set to record their positions at a rate of 2 times per second. The R/V Shark(15BIM13)and the R/V Chum(15BIM13)recorded their GPS positions at a rate of 10 times per second.
The base receivers and the rover receiver recorded their positions concurrently at intervals equal to or slower than that of the base station throughout the survey. The GPS navigation data was acquired and processed in the World Geodetic Datum of 1984 (WGS84 G1150). For all vessels the navigation was post-processed to obtain DGPS.
Process_Date: 2016
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Nancy T. DeWitt
Contact_Organization:
U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
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 all vessels at 100-milliseconds (ms) using an Odom CV100 echo sounder system with a 200 kilohertz (kHz) transducer. Boat motion was recorded on the R/V Sallenger (15BIM10) and the R/V Jabba Jaw (15BIM11) at 50-ms intervals using a TSS Dynamic Motion Sensor (TSS DMS-05). The R/V Shark (15BIM12) and the R/V Chum (15BIM13) did not record boat motion. To minimize motion errors, these vessels recorded GPS at a high rate (10 times per second) 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 Sontek Castaway CTD units to record changes in water column speed of sound (SOS).
Process_Date: 2016
Source_Produced_Citation_Abbreviation:
HYPACK raw data files (.RAW), HYPACK target files (.TGT), and SOS files (.txt).
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Nancy T. DeWitt
Contact_Organization:
U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
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 (BH17 and WDAU) are the time-weighted average of values obtained from the National Geodetic Survey's (NGS) On-Line Positioning User Service (OPUS). The coordinates were imported into the post-processing software GrafNav (Waypoint Product Group) version 8.6. 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 were used. These options 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 each roving vessels respective recording rate, and then exported in American Standard Code for Information Interchange (ASCII) text format. This file then 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.
Process_Date: 2016
Source_Produced_Citation_Abbreviation:
Post-processed differential navigation data for the rover (boat) in ASCII text format.
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Nancy T. DeWitt
Contact_Organization:
U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
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 processing: All data were processed using CARIS HIPS and SIPS (Hydrographic Information Processing System and Sonar Information Processing System) version 9.1.1. The raw HYPACK (15BIM10 used version 14.0.9.47; 15BIM11 used version13.0.9.28; 15BIM12 and 15BIM13 used version 2013A) 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. The exported ASCII files were then combined into one large file for further quality assurance and quality control.
Source_Used_Citation_Abbreviation:
Post-processed differential navigation data files, HYPACK RAW bathymetric data files, HYPACK target (.TGT) files, and SOS (.txt) files all in ASCII text format.
Process_Date: 2016
Source_Produced_Citation_Abbreviation:
15BIM10_SBB_Level_03_ITRF00.txt
15BIM11_SBB_Level_03_ITRF00.txt
15BIM12_SBB_Level_03_xxx_ITRF00_Draft2.txt
15BIM13_SBB_Level_03_xxx_ITRF00_Draft2.txt
DI_2015_326_FA_SBB_Level_05_ITRF00.txt (combination of all above files)
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Nancy T. DeWitt
Contact_Organization:
U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
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 Error Analysis: The data were edited for outliers in the Single-Beam Editor of CARIS and then 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. This ASCII file was then imported into ArcMap version 10.3 and reviewed for outliers. An Esri ArcMap Ad-In program script was written locally to evaluate the elevation differences at the intersection of crossing lines. If discrepancies were found at a crossing, the source of the discrepancies was identified and if needed the line or segment of data points in error was statically adjusted or removed.
Source_Used_Citation_Abbreviation: DI_2015_326_FA_SBB_Level_05_ITRF00.txt
Process_Date: 2016
Source_Produced_Citation_Abbreviation:
Dauphin_Island_2015_SBB_ITRF00_xyz.shp
Dauphin_Island_2015_SBB_ITRF00_xyz.txt
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Nancy T. DeWitt
Contact_Organization:
U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing and physical address
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 single-beam elevations were examined for spatial distribution and vertical agreement. A triangulated irregular network (TIN) was generated with the x,y,z point data and constrained using a polygon shoreline. The polygon shoreline was created in ArcGIS version 10.3.1 from using the zero line extracted from the 2015 USGS Dauphin Island Lidar dataset. The TIN was generated using the ArcToolbox 3D Analysts Data Management Tool “Create TIN”. This TIN file was then sent through the 3D Analyst Conversion Tool “TIN to Raster” using the natural neighbor method at 50 meter (m) by 50 m spacing to produce the raster Digital Elevation Model (DEM). Lastly, the raster was clipped to the survey extent using Spatial Analyst Extract tool “Extract by Mask”. The DEM was then clipped to the raster mask using the ArcGIS Spatial Analyst "extract by raster mask" tool.
Source_Used_Citation_Abbreviation:
DI_2015_326_FA_SBB_Level_05_ITRF00.shp
Dauphin_2015_shoreline_ITRF00.shp
Process_Date: 2016
Source_Produced_Citation_Abbreviation: Dauphin_Island_2015_ITRF00_50_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:
This trackline file was created from the all-encompassing x,y,z point file for USGS FAN 2015-326-FA (15BIM10, 15BIM11, 15BIM12 and 15BIM13) in Esri ArcGIS version 10.3 using the XTools Pro extension, version 11.1. The x,y,z data point shapefile was sent through the "XTools" feature conversion tool, "make polylines from points". Within "XTools" feature conversion selection window, the following items were selected. The "group by field selection" was set to use the HYPACK line name attribute and the "input feature order - order by field" was set to use the FID attribute. The resultant polyline shapefile was then projected in WGS84 Universal Transverse Mercator (UTM) Zone 16 North.
Source_Used_Citation_Abbreviation: DI_2015_326_FA_SBB_Level_05_ITRF00.shp
Process_Date: 2016
Source_Produced_Citation_Abbreviation: Dauphin_Island_2015_SBB_ITRF00_tracklines.shp
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: U.S.
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
