Single-Beam Bathymetry Data Collected in March 2021 from Grand Bay and Point Aux Chenes Bay, Mississippi/Alabama

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Frequently anticipated questions:

What does this data set describe?

Title:
Single-Beam Bathymetry Data Collected in March 2021 from Grand Bay and Point Aux Chenes Bay, Mississippi/Alabama
Abstract:
Scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center (USGS SPCMSC) in St. Petersburg, Florida, conducted a bathymetric survey of Point Aux Chenes Bay and a small portion of Grand Bay, Mississippi/Alabama, from March 3-6, 2021. Efforts were supported by the Estuarine and MaRsh Geology project (EMRG), and the data described will provide baseline bathymetric information for future research investigating wetland/marsh evolution, sediment transport, and recent and long-term geomorphic change. The data will also support modeling of future changes in response to restoration efforts and storm impacts. During this study, bathymetry data were collected aboard two personal watercrafts (PWC) outfitted with single-beam echosounders.
Supplemental_Information:
For the single-beam bathymetry data, the differential positioning was obtained through post-processing the base station data to the rover. This dataset was transformed from the initial World Geodetic System of 1984 (WGS84) G1762 datum to North American Datum of 1983 (NAD83) reference frame and the North American Vertical Datum of 1988 (NAVD88), using the GEOID12A model (National Oceanic and Atmospheric Administration National Geodetic Survey (NOAA NGS) VDatum software version 4.1 - http://vdatum.noaa.gov/). Similar surveys have occurred in years prior, please see USGS Data Series 1070 for more information regarding acquisition and processing methods (DeWitt and others, 2017).
  1. How might this data set be cited?
    Stalk, Chelsea A., Wilcox, Hunter S., Passeri, Davina L., Smith, Christopher G., Smith, Kathryn E.L., and Terrano, Joseph F., 20210916, Single-Beam Bathymetry Data Collected in March 2021 from Grand Bay and Point Aux Chenes Bay, Mississippi/Alabama:.

    This is part of the following larger work.

    Stalk, Chelsea A., Wilcox, Hunter S., Passeri, Davina L., Smith, Christopher G., Smith, Kathryn E.L., and Terrano, Joseph F., 20210916, Single-Beam Bathymetry Data Collected in March 2021 from Grand Bay and Point Aux Chenes Bay, Mississippi/Alabama: U.S. Geological Survey data release doi:10.5066/P93ZM9MK, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, Florida.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.494092
    East_Bounding_Coordinate: -88.395754
    North_Bounding_Coordinate: 30.387609
    South_Bounding_Coordinate: 30.295703
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 03-Mar-2021
    Ending_Date: 06-Mar-2021
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: tabular, vector, and raster digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (1,791,276)
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 16
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -87.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.6096
      Ordinates (y-coordinates) are specified to the nearest 0.6096
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum 1988
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?
    PointAuxChenes_2021_SBES_NAD83_UTM16N_NAVD88_G12A_xyz.txt and PointAuxChenes_Reefs_2021_SBES_NAD83_UTM16N_NAVD88_G12A_xyz.txt.
    Comma-delimited x,y,z text file containing location, elevation, and date information collected with personal watercraft and ground-based GPS within Point Aux Chenes Bay, MS. (Source: U.S. Geological Survey)
    NAD83_UTM16N_X
    NAD83 UTM x-axis coordinate (Zone 16N) (Source: U.S. Geological Survey)
    Range of values
    Minimum:356411.150
    Maximum:368246.000
    Units:meters
    NAD83_UTM16N_Y
    NAD83 UTM y-axis coordinate (Zone 16N) (Source: U.S. Geological Survey)
    Range of values
    Minimum:3352495.721
    Maximum:3359404.905
    Units:meters
    NAVD88_G12A
    z-value (elevation) in NAVD88 Geoid 12A (Source: U.S. Geological Survey)
    Range of values
    Minimum:-4.290
    Maximum:-0.105
    Units:meters
    NAD83_Lat
    NAD83 UTM y-axis coordinate (Zone 16N) (Source: U.S. Geological Survey)
    Range of values
    Minimum:30.295798
    Maximum:30.358667
    Units:Decimal Degrees
    NAD83_Long
    NAD83 UTM x-axis coordinate (Zone 16N) (Source: U.S. Geological Survey)
    Range of values
    Minimum:-88.493469
    Maximum:-88.370816
    Units:Decimal Degrees
    Year
    Calendar Year of data acquisition (Source: U.S. Geological Survey)
    Range of values
    Minimum:2021
    Maximum:2021
    DOY
    Day of Year of data acquisition (Source: U.S. Geological Survey)
    Range of values
    Minimum:62
    Maximum:65
    UTC_Time
    Coordinated Universal Time (UTC) time of data acquisition (Source: U.S. Geological Survey)
    Range of values
    Minimum:15:18:09.32
    Maximum:23:35:10.38
    Hypack_Line
    Identifier assigned to each Hypack line. (Source: HYPACK/U.S. Geological Survey) Sub-FAN identifier (21CCT01 or 21CCT02) followed by DOY, line number and start of line UTC time, separated by underscores.
    MiddleBay_2021_SBES_NAD83_UTM16N_NAVD88_G12A_xyz.txt
    Comma-delimited x,y,z text file containing location, elevation, and date information collected with personal watercraft and ground-based GPS within Middle Bay, MS/AL. (Source: U.S. Geological Survey)
    NAD83_UTM16N_X
    NAD83 UTM x-axis coordinate (Zone 16N) (Source: U.S. Geological Survey)
    Range of values
    Minimum:364139.205
    Maximum:365884.658
    Units:meters
    NAD83_UTM16N_Y
    NAD83 UTM y-axis coordinate (Zone 16N) (Source: U.S. Geological Survey)
    Range of values
    Minimum:3361048.535
    Maximum:3362562.730
    Units:meters
    NAVD88_G12A
    z-value (elevation) in NAVD88 Geoid 12A (Source: U.S. Geological Survey)
    Range of values
    Minimum:-2.327
    Maximum:-0.281
    Units:meters
    NAD83_Lat
    NAD83 UTM y-axis coordinate (Zone 18N) (Source: U.S. Geological Survey)
    Range of values
    Minimum:30.373794
    Maximum:30.387504
    Units:Decimal Degrees
    NAD83_Long
    NAD83 UTM x-axis coordinate (Zone 18N) (Source: U.S. Geological Survey)
    Range of values
    Minimum:-88.413998
    Maximum:-88.395852
    Units:Decimal Degrees
    Year
    Calendar Year of data acquisition (Source: U.S. Geological Survey)
    Range of values
    Minimum:2021
    Maximum:2021
    DOY
    Day of Year of data acquisition (Source: U.S. Geological Survey)
    Range of values
    Minimum:62
    Maximum:62
    UTC_Time
    UTC Time of data acquisition (Source: U.S. Geological Survey)
    Range of values
    Minimum:17:30:39.24
    Maximum:19:19:03.81
    Hypack_Line
    Identifier assigned to each Hypack line. (Source: HYPACK/U.S. Geological Survey) Sub-FAN identifier (21CCT01 or 21CCT02) followed by DOY, line number and start of line UTC time, separated by underscores.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Chelsea A. Stalk
    • Hunter S. Wilcox
    • Davina L. Passeri
    • Christopher G. Smith
    • Kathryn E.L. Smith
    • Joseph F. Terrano
  2. Who also contributed to the data set?
    Funding and (or) support for this study was provided by the USGS Coastal and Marine Geology Program. The authors are grateful to Jonathan Pitchford, with the Grand Bay National Research Refuge, who provided permitting, access, and assistance with field logistics. This document was improved by reviews from Andrew Farmer and Breanna Williams of the USGS - St. Petersburg, Florida.
  3. To whom should users address questions about the data?
    Chelsea A. Stalk
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Electronics Technician (Marine Instrumentation)
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    cstalk@usgs.gov

Why was the data set created?

These datasets, Grand_Bay_2021_SBES_xyz.zip and Point_Aux_Chenes_2021_SBES_xyz.zip in conjunction with all other provided data in this release, consist of single-beam bathymetry data collected within Grand Bay and Point Aux Chenes Bay, onboard two personal watercraft (PWC) vessels during the March 2021 Grand Bay and Point Aux Chenes Bay, Mississippi/Alabama survey. Additional survey and data details are available in the Coastal and Marine Geoscience Data System (CMGDS)at, https://cmgds.marine.usgs.gov/fan_info.php?fan=2021-307-FA.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2021 (process 1 of 8)
    GPS Acquisition: Two Geographic Positioning System (GPS) base stations were established throughout the survey area, both of which were located on NPS established benchmarks. Benchmark 189A (PID: D05977) was located to the north-north west of the survey area near the railroad tracks at the entrance of the Grand Bay National Estuarine Research Reserve (GNDNERR), B166 (PID: D05987) was located northwest of the survey area at the boat launch location used for this survey. The base stations were continually occupied and equipped with a Spectra Precision SP90M (B166) and a Spectra Precision Proflex 800 (189A) GPS receiver recording full-carrier-phase positioning signals (L1/L2) from satellites via Thales Choke-ring antennas, recording at a rate of 0.1 s. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Chelsea A. Stalk
    Electronics Technician (Marine Instrumentation)
    600 4th St. S
    St. Petersburg, FL
    USA

    727-502-8000 (voice)
    cstalk@usgs.gov
    Date: 2021 (process 2 of 8)
    Single-Beam Bathymetry Acquisition: The single-beam bathymetric data were collected under the USGS Field Activity Number (FAN) 2021-307-FA, which encompass data from two separate survey platforms; the RV Shark (WVR1, 21CCT01), a 12-ft (foot) Yamaha PWC which collected 28.51 line-km (97 lines), and the RV Chum (WVR2, 21CCT02), an additional 12-ft Yamaha PWC which collected 190.28 line-km (91 lines). Boat motion was recorded at 50-millisecond (ms) intervals using a SBG Ellipse A #1 motion sensor aboard each PWC. HYPACK (version 18.1.8.0), 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 using an Odom echotrac CV100 sounder with a 200-kilohertz (kHz) transducer. Data from the GPS receiver, motion sensor, and fathometer were recorded in real-time aboard all vessels independently and merged 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 profile (SVP) measurements were collected using three SonTek Castaway Conductivity, Temperature, and Depth (CTD) instruments. The instruments were periodically cast overboard to observe changes in water column speed of sound (SOS). A total of 74 successful sound velocity casts were taken throughout the survey at an average depth of 0.94 meters, and on average produced a sound velocity of 1492.32 meters per second (m/s). Person who carried out this activity:
    Chelsea A. Stalk
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Electronics Technician (Marine Instrumentation)
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    cstalk@usgs.gov
    Date: 2021 (process 3 of 8)
    Differentially Corrected Navigation Processing: The coordinate values of the GPS base stations are the time-weighted average of values obtained from NGS OPUS. The base station coordinates were imported into GrafNav version 8.7 (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 the trajectories between the base and the rover were free of erroneous solutions and resulted 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 0.1 s and exported in American Standard Code for Information Interchange (ASCII) text format. Concurrent post-processed navigation data to single-beam data points replace the uncorrected rover positions, recorded during acquisition, in subsequent processing steps. The GPS data were processed and exported in the World Geodetic System of 1984 (WGS84) G1762 geodetic datum. Person who carried out this activity:
    Chelsea A. Stalk
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Electronics Technician (Marine Instrumentation)
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    cstalk@usgs.gov
    Date: 2021 (process 4 of 8)
    All data were processed using CARIS HIPS and SIPS (Hydrographic Information Processing System and Sonar Information Processing System) version 11.3.0. The raw HYPACK data files were imported into CARIS, the differentially corrected navigation files were imported using the generic data parser tool, and any SVP casts were entered and edited using the SVP editor. 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 (G1762), ellipsoid height in meters. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Chelsea A. Stalk
    Electronics Technician (Maine Instrumentation)
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    cstalk@usgs.gov
    Date: 2021 (process 5 of 8)
    Quality Control, Quality Assurance (QA/QC) and Uncertainty Analysis: All single-beam data exported from CARIS and elevation data exported from GrafNav, were imported into Esri ArcMap version 10.6.0 utilizing the create feature class from an XY table function and plotted in 0.25-m color coded intervals utilizing symbology functions. First, all data were visually scanned for any obvious outliers or problems. Next, a trackline shapefile was produced using X-tools Pro (version 21.1.4313) "Make Polylines from Points" function for each survey platform. Utilizing both the x,y,z (point) and trackline (polyline) shapefiles, a Python script evaluated elevation differences at the intersection of crossing tracklines by calculating the elevation difference between points at each intersection using an inverse distance weighting equation with a search radius of 1 m. The RMS error for WVR1 (21CCT01), when crossing a trackline it previously surveyed, was 5.06 cm and when WVR2 (21CCT02) crossed a track line it previously surveyed, the RMS error was 4.60 cm. Once individual platform statistics were obtained, all data were merged, and crossing analysis yielded a 5.32 cm RMS error. These merged files were separated into three survey areas: Point Aux Chenes, Point Aux Chenes Reefs and Middle Bay. These files were then exported from Esri ArcMap as x,y,z text (.txt) files using the X-tools Pro "table to text" function, and made available in the download section of this data release, along with the populated trackline shapefiles. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Chelsea A. Stalk
    Electronics Technician (Marine Instrumentation)
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    cstalk@usgs.gov
    Data sources used in this process:
    • 21CCT01_PointAuxChenes_WVR1_SBES_WGS84_UTM16N_Level_03_xyz.txt 21CCT02_PointAuxChenes_WVR2_SBES_WGS84_UTM16N_Level_03_xyz.txt
    Data sources produced in this process:
    • PointAuxChenes_2021_SBES_WGS84_UTM16N_xyz.txt PointAuxChenes_Reefs_2021_SBES_WGS84_UTM16N_xyz.txt MiddleBay_2021_SBES_WGS84_UTM16N_xyz.txt PointAuxChenes_2021_SBES_WGS84_UTM16N_Tracklines.shp PointAuxChenes_Reefs_2021_SBES_WGS84_UTM16N_Tracklines.shp MiddleBay_2021_SBES_WGS84_UTM16N_Tracklines.shp
    Date: 2021 (process 6 of 8)
    Datum Transformation: NOAA's VDatum v.4.1 was used to transform the single-beam data points (x,y,z data) from their data acquisition datum (WGS84 G1762) to NAD83 NAVD88 using the NGS geoid model of 2012A (GEOID12A). For conversion from the WGS84 ellipsoid to NAVD88, there is a total of 7.616 cm of uncertainty in the transformation (NOAA/NGS's VDatum: Estimation of Vertical Uncertainties in VDatum, https://vdatum.noaa.gov/docs/est_uncertainties.html). Resultant data files have been made available in the downloads section of this data release. Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Chelsea A. Stalk
    Electronics Technician (Marine Instrumentation)
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    cstalk@usgs.gov
    Data sources used in this process:
    • PointAuxChenes_2021_SBES_WGS84_UTM16N_xyz.txt PointAuxChenes_Reefs_2021_SBES_WGS84_UTM16N_xyz.txt MiddleBay_2021_SBES_WGS84_UTM16N_xyz.txt
    Data sources produced in this process:
    • PointAuxChenes_2021_SBES_NAD83_UTM16N_NAVD88_G12A_xyz.txt PointAuxChenes_Reefs_2021_SBES_NAD83_UTM16N_NAVD88_G12A_xyz MiddleBay_2021_SBES_NAD83_UTM16N_NAVD88_G12A_xyz.txt
    Date: 2021 (process 7 of 8)
    Shoreline Preparation: In order to provide the most accurate representation of the bathymetry within the nearshore areas, shoreline data was prepared and used in conjunction with the x,y,z data during subsequent processing steps. Shoreline polyline data provided in Terrano and others (2021), was first converted to points utilizing the XTools Function "Polylines to Points". Utilizing the "Buffer" analysis tool, a 100 m buffer was generated around the Point Aux Chenes and Middle Bay tracklines. The shoreline points were then clipped using the "Clip" analysis tool to each generated buffer file to ensure only shoreline points that fall within 100 m from a bathymetry point were utilized for further processing. Some manual editing of the resultant shoreline point file was necessary to ensure proper representation of the bathymetry extent. An integer field was added to the shoreline points attribute table named, "NAVD88_G12A" and the field populated with a zero-value utilizing the Field Calculator function to represent a zero elevation at the shoreline extent. The resultant point shapefile has been made available in the download section of this data release (Stalk and others, 2021). The shoreline points were then converted to a polygon utilizing the XTools Pro "Points to Polygons" function to establish an extent file to be used in later processing steps. Polygon vertices were manually added using the Editor tool to the western and eastern portions of Point Aux Chenes Bay, placed at the approximate land-water intersection using Esri's Imagery base map, as well as along the offshore extent of the x,y,z data. The resultant extent or coverage file was utilized in subsequent processing steps and has also been made available in the data download section of this data release (Stalk and others, 2021). Person who carried out this activity:
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Chelsea A. Stalk
    Electronics Technician (Marine Instrumentation)
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    cstalk@usgs.gov
    Data sources used in this process:
    • GB_2020_shoreline.shp
    Data sources produced in this process:
    • PointAuxChenes_2020_ShorelinePoints.shp MiddleBay_2020_ShorelinePoints.shp PointAuxChenes_2021_SBES_Coverage.shp MiddleBay_2021_SBES_Coverage.shp
    Date: 2018 (process 8 of 8)
    Create Digital Elevation Model: The transformed x,y,z data described in the previous processing step were imported into ArcMap using the "Create Feature Class From XY Table" tool. The dataset, along with the generated shoreline points were used to create a triangulated irregular network (TIN) using the "Create TIN" tool. The TIN was subsequently converted into a raster file using the "TIN to Raster" tool with a cell size of 10 meters for both the Point Aux Chenes Bay and Middle Bay survey areas. The resultant raster was then clipped utilizing the "Extract by Mask" Analysis tool, utilizing the coverage file produced in the previous step. The final digital elevation model (DEM) was then exported from ArcMap as a 32-bit floating GeoTiff, utilizing the Natural Neighbor algorithm, and made available within the data downloads section of this data release (Stalk and others, 2021). As a part of standard QA/QC procedures, each DEM was compared to the associated x,y,z data, and associated RMSe values were populated. The Point Aux Chenes Bay DEM has a RMSe value of 0.027 m and the Middle Bay DEM, 0.036 m respectively. Person who carried out this activity:
    Geological Survey St. Petersburg Coastal and Marine Science Center Geological Survey
    Attn: Chelsea A. Stalk
    Electronics Technician (Marine Instrumentation)
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    cstalk@usgs.gov
    Data sources used in this process:
    • PointAuxChenes_2021_SBES_NAD83_UTM16N_NAVD88_G12A_xyz.txt MiddleBay_2021_SBES_NAD83_UTM16N_NAVD88_G12A_xyz.txt PointAuxChenes_2020_ShorelinePoints.shp MiddleBay_2020_ShorelinePoints.shp PointAuxChenes_2021_SBES_Coverage.shp MiddleBay_2021_SBES_Coverage.shp
    Data sources produced in this process:
    • PointAuxChenes_2021_NAD83_NAVD88_G12A_10m_DEM.tif MiddleBay_2021_NAD83_NAVD88_G12A_10m_DEM.tif
  3. What similar or related data should the user be aware of?
    DeWitt, Nancy T., Stalk, Chelsea A., Smith, Christopher G., Locker, Stanley D., Fredericks, Jake J., McCloskey, Terrance A., and Wheaton, Cathryn J., 20171201, Single-Beam Bathymetry Data Collected in 2015 from Grand Bay, Alabama-Mississippi: U.S. Geological Survey Data Series DS 1070, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL.

    Online Links:

    Terrano, Joseph F., Smith, Kathryn E.L., Pitchford, Jonathan L., Archer, Michael, and Brochard, Michael, 20210723, Shorelines from High-resolution WorldView Satellite Imagery, Real-time Kinematic Global Positioning Data, and Aerial Imagery for 2013 to 2020 for Study Sites Within Grand Bay National Estuarine Research Reserve, Mississippi: U.S. Geological Survey data release doi:10.5066/P9W8TNQM, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL.

    Online Links:

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    The accuracy of the data is determined during data collection. This dataset is derived from a single field survey using identical equipment, set-ups, and staff; therefore, the dataset is internally consistent. Methods are employed to maintain data collection consistency aboard the platforms. During mobilization, each piece of equipment was isolated to obtain internal- and external-offset measurements with respect to the survey platform. All the critical measurements were recorded manually and then digitally entered into their respective programs. Offsets between the single-beam transducers, motion reference units, and the antenna reference point (ARP) were measured and accounted for in post-processing. Differential Global Positioning System (DGPS) coordinates were obtained using post-processing software packages (NGS OPUS, and Waypoint Product Group GrafNav, version 8.7).
  2. How accurate are the geographic locations?
    All static base station sessions were processed through the Online Positioning User Service (OPUS) maintained by the NOAA NGS. The OPUS solutions were entered into a spreadsheet to compute a final, time-weighted position (latitude, longitude, and ellipsoid height) for each base station. The time-weighted positions for all base stations occupying established NPS benchmarks (B166 [PID: D05987] and 189A [PID: D05977]) were compared against the provided NPS coordinates as well as coordinate solutions from previous survey occupations. The time-weighted positions were within 3 standard deviations of the 2015 coordinate positions established during the initial survey (DeWitt and others, 2017), and therefore, to isolate variables when comparing the two datasets, the previous position coordinates were used in subsequent processing steps. The horizontal variability of the base station coordinates at B166 and 189A were determined by calculating the maximum difference of any individual occupation from the time-weighted average latitude and longitude values B166: 0.00010 seconds (s) latitude (0.26 centimeters [cm]), 0.00008 seconds longitude (0.20 cm); 189A: 0.00003 (0.08 cm) seconds latitude, 0.00007 seconds longitude (0.18 cm).
  3. How accurate are the heights or depths?
    All static base station sessions were processed through OPUS, which is maintained by NOAA and the NGS. The OPUS solutions were entered into a spreadsheet to compute a final, time-weighted position (latitude, longitude, and ellipsoid height) for each base station. The time-weighted positions for all base stations occupying established NPS marks (B166 [PID: D05987] and 189A [PID: D05977]) were compared against the provided NPS coordinates as well as coordinate solutions from previous survey occupations. The time-weighted positions were within 3 standard deviations of the 2015 coordinate positions established during the initial survey (DeWitt and others, 2017), and therefore, to isolate variables when comparing the two datasets, the previous position coordinates were used in subsequent processing steps. The vertical variability of the base station coordinates were determined by calculating the maximum difference of any individual occupation from the time-weighted average ellipsoid height values (B166: +/- 0.5 cm; 189A: +/- 2.3 cm). The base station erected on 189A benchmark served as the secondary for the survey, and data acquired did not need to be utilized for further processing. The kinematic (rover) trajectories were processed using GrafNav version 8.7 software by Novatel, Inc. Occurrences where a personal watercraft trackline crosses itself and the other PWC were evaluated to determine vertical uncertainty. The calculated root mean square (RMS) uncertainty for the PWC's are 0.05 meters (m) for both platforms individually, and when crossing each other.
  4. Where are the gaps in the data? What is missing?
    This data release contains horizontal position and vertical elevation x,y,z single-beam data from March 2021 collected within Grand Bay and Point Aux Chenes Bay, MS/AL. Users are advised to read the complete metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    These data were collected during one field activity with consistent instrument calibrations.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
Use_Constraints:
Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey requests to be acknowledged as originator of these data in future products or derivative research. These data should not be used for navigational purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    Chelsea A. Stalk
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Electronics Technician (Marine Instrumentation)
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    cstalk@usgs.gov
  2. What's the catalog number I need to order this data set? Downloadable Data
  3. What legal disclaimers am I supposed to read?
    This digital publication was prepared by an agency of the United States Government. Although these data were processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 16-Sep-2021
Last Reviewed: 01-Sep-2021
Metadata author:
Chelsea A. Stalk
U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
Electronics Technician (Marine Instrumentation)
600 4th Street South
St. Petersburg, FL
USA

(727) 502-8000 (voice)
cstalk@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/GrandBay_PointAuxChenes_2021_metadata.faq.html>
Generated by mp version 2.9.50 on Tue Sep 21 18:18:49 2021