Single-Beam Bathymetric Data Collected in 2012 from the Chandeleur Islands, Louisiana (U.S. Geological Survey Field Activity Number 12BIM04)

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Frequently anticipated questions:


What does this data set describe?

Title:
Single-Beam Bathymetric Data Collected in 2012 from the Chandeleur Islands, Louisiana (U.S. Geological Survey Field Activity Number 12BIM04)
Abstract:
As part of the Barrier Island Evolution Research Project, scientists from the U.S. Geological Survey's St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys off the northern Chandeleur Islands, Louisiana, in July of 2012. The overall objective of the study is to better understand barrier-island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual timescales (1-5 years). The collection of geophysical data will allow us to identify relationships between the geologic history of the island and its present day morphology and sediment distribution. This mapping effort was the first in a series of three planned surveys in this area. High resolution geophysical data collected in each of 3 consecutive years along this rapidly changing barrier-island system will provide a unique time-series dataset that will significantly further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over short time scales (1-5 years). This report serves as an archive of processed interferometric swath and single-beam bathymetry data that were collected during two cruises (USGS Field Activity Numbers 12BIM03 and 12BIM04) along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge, Louisiana, in July of 2012. Geographic information system data products include a 50 m-cell-size interpolated bathymetry grid surface, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata.
Supplemental_Information:
The swath bathymetry data were collected and processed in the ITRF2005 geodetic reference ellipsoid whereas the single-beam data were collected and processed in WGS84 (G1150)/ITRF00. Both datasets were subsequently transformed horizontally to NAD83 and then vertically to NAVD88 and MLLW, using the GEOID09 model with National Oceanic and Atmospheric Administration (NOAA) VDatum version 3.2 transformation software (http://vdatum.noaa.gov/). The final NAD83, NAVD88 x,y,z position data from each survey were merged to generate a digital elevation model with a cell-size resolution of 50 meters.
  1. How might this data set be cited?
    U.S. Geological Survey, 2014, Single-Beam Bathymetric Data Collected in 2012 from the Chandeleur Islands, Louisiana (U.S. Geological Survey Field Activity Number 12BIM04):.

    Online Links:

    This is part of the following larger work.

    DeWitt, Nancy T., Bernier, Julie C., Pfeiffer, William R., Miselis, Jennifer L., Flocks, James G., Reynolds, B.J., Wiese, Dana S., and Kelso, Kyle W., 2014, Coastal Bathymetry and Backscatter Data Collected in 2012 from the Chandeleur Islands, Louisiana: U.S. Geological Survey Data Series 847, U.S. Geological Survey, St. Petersburg, Florida.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.915048
    East_Bounding_Coordinate: -88.762774
    North_Bounding_Coordinate: 30.070733
    South_Bounding_Coordinate: 29.867602
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 20-Jul-2012
    Ending_Date: 03-Aug-2012
    Currentness_Reference:
    data collection interval
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: ASCII
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
    2. What coordinate system is used to represent geographic features?
  7. How does the data set describe geographic features?
    12BIM04_SBB_ITRF00_xyz.txt
    ASCII text file containing the processed single-beam bathymetry x,y,z point data in the International Terrestrial Reference Frame of 2000 (ITRF00). (Source: USGS)
    12BIM04_SBB_NAD83_NAVD88_GEOID09_xyz.txt
    ASCII text file containing the processed single-beam bathymetry x,y,z point data transformed from the International Terrestrial Reference Frame of 2000 (ITRF00) to the North American Datum of 1983 (NAD83) geodetic datum and North American Vertical Datum of 1988 (NAVD88) orthometric height, derived using the GEOID09 model. (Source: USGS)
    12BIM04_SBB_NAD83_MLLW_xyz.txt
    ASCII text file containing the processed single-beam bathymetry x,y,z point data transformed from the International Terrestrial Reference Frame of 2000 (ITRF00) to the North American Datum of 1983 (NAD83) geodetic datum and Mean Lower Low Water (MLLW) tidal datum. (Source: USGS)
    ITRF00_X
    ITRF00 X-coordinate (easting) of sample point, in meters (Source: CARIS)
    Range of values
    Minimum:315408.432
    Maximum:329748.954
    Resolution:0.001
    ITRF00_Y
    ITRF00 y-coordinate (northing) of sample point, in meters (Source: CARIS)
    Range of values
    Minimum:3305646.659
    Maximum:3327936.889
    Resolution:0.001
    Ellipsoid
    TRF00 ellipsoid height of sample point, in meters (Source: CARIS)
    Range of values
    Minimum:-41.138
    Maximum:-28.062
    Resolution:0.001
    NAD83_X
    NAD83 X-coordinate (easting) of sample point, in meters (Source: VDatum version 3.2)
    Range of values
    Minimum:315409.167
    Maximum:329749.685
    Resolution:0.001
    NAD83_Y
    NAD83 Y-coordinate (northing) of sample point, in meters (Source: VDatum version 3.2)
    Range of values
    Minimum:3305646.072
    Maximum:3327936.297
    Resolution:0.001
    NAVD88_G09
    The Z-Coordinate in orthometric height (NAVD88)of the sample with respect to Geoid09, in meters (Source: VDatum version 3.2)
    Range of values
    Minimum:-13.195
    Maximum:-0.144
    Resolution:0.001
    MLLW
    The Z-Coordinate as tidal datum (MLLW) of the sample, in meters. (Source: VDatum version 3.2)
    Range of values
    Minimum:0.085
    Maximum:13.148
    Resolution:0.001
    DOY
    Day of the year the data was collected (Source: USGS)
    Range of values
    Minimum:205
    Maximum:213
    Resolution:1
    Year
    Year data was collected (Source: USGS) Character String - 2012
    DataType
    Data type of the sample point. SBB for Single-Beam Bathymetry (Source: USGS) Character String - SBB

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
    U.S. Geological Survey, Coastal and Marine Geology Program, St. Petersburg Coastal and Marine Science Center
  3. To whom should users address questions about the data?
    Nancy T. DeWitt
    U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

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

Why was the data set created?

This zip archive contains processed x,y,z data points for the single-beam bathymetry data collected in July 2012 around the Chandeleur Islands, Louisiana. The processed single-beam soundings are provided as ASCII x,y,z point data.

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: 2013 (process 1 of 6)
    GPS Base Station Acquisition: The GPS base stations were assembled at temporarily installed USGS benchmarks (TMRK and BERM)on the Chandeleur Islands, La. The GPS receivers recorded the 12-channel full-carrier- phase positioning signals (L1/L2) from the satellites via the Thales choke-ring antenna. This GPS instrument combination was duplicated on the survey vessel also known as the rover. The base receiver and the rover receiver recorded their positions concurrently at 1-second (s) recording intervals throughout the survey. The single-beam data for USGS Cruise 12BIM04 was acquired with hydrographic software HYPACK version 10.0.5.31. All data strings from the instruments were streamed in real time through HYPACK. Person who carried out this activity:
    Nancy T. DeWitt
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Date: 2013 (process 2 of 6)
    Single-Beam Bathymetry Acquisition: The single-beam bathymetric data were collected aboard the 22-foot R/V TwinVee. Boat motion was recorded at 50-millisecond (ms) intervals using 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 using a Knudsen 320BP echosounder system with 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, with each device string 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). Person who carried out this activity:
    Nancy T. DeWitt
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Date: 2013 (process 3 of 6)
    Differentially Corrected Navigation Processing: The coordinate values of the GPS base station (TMRK and BERM) are the time-weighted average of values obtained from the National Geodetic Survey's On-Line Positioning User Service (OPUS). Each base station GPS file was processed to the roving survey vessel GPS file using GrafNav version 8.10 (Waypoint Product Group). During this process, steps were taken to ensure that the trajectory produced from the base to the rover was clean and produced 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. From these processes, a single differentially corrected, precise position file, at 1-s intervals, was generated for each roving 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 the World Geodetic System of 1984 (WGS84) (G1150) geodetic datum which is equivalent to ITRF00. Person who carried out this activity:
    Nancy T. DeWitt
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Data sources produced in this process:
    • 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.
    Date: 2013 (process 4 of 6)
    Single-beam bathymetry processing: All data were processed using 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 speed of sound (SOS)) were then merged and geometrically corrected in CARIS to produce processed x,y,z data. Next, the data were edited for outliers and 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. Person who carried out this activity:
    Nancy T. DeWitt
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Data sources produced in this process:
    • 12BIM04_SBB_03_ITRF00_xxx.txt
    Date: 2013 (process 5 of 6)
    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 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 line in error was statically adjusted or removed. The shapefile was exported as an ASCII table using Esri's ArcMap XTools Pro table operations, export table to text. Person who carried out this activity:
    Nancy T. DeWitt
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Data sources used in this process:
    • 12BIM04_SBB_03_ITRF00_xxx.txt
    Data sources produced in this process:
    • 12BIM04_SBB_ITRF00_xyz.txt
    Date: 2013 (process 6 of 6)
    Datum Transformation: The text file 12BIM04_SBB_03_ITRF00.txt was converted two separate times using VDatum version 3.2 producing two separate files with different vertical datums. The first transformation was from the data acquisition and processing datum (International Terrestrial Reference Frame of 2000, ITRF00) to the North American Datum of 1983 (NAD83) reference frame and the North American Vertical Datum of 1988 (NAVD88) orthometric height using the National Geodetic Survey (NGS) geoid model of 2009 (GEOID09). The second transformation was from ITRF00 to NAD83 for the horizontal reference frame and Mean Lower Low Water (MLLW) tidal datum using GEOID09. Person who carried out this activity:
    Nancy T. DeWitt
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Data sources used in this process:
    • 12BIM04_SBB_ITRF00_03.txt
    Data sources produced in this process:
    • 12BIM04_SBB_NAD83_NAVD88_GEOID09_xyz.txt
    • 12BIM04_SBB_NAD83_MLLW_xyz.txt
  3. What similar or related data should the user be aware of?

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 from one research cruise and is therefore internally consistent. Methods are 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. All the critical measurements are recorded manually and digitally entered into their respective programs. 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 Knudsen 320BP. Differential geographic positioning system(DGPS) data were obtained using post-processing software GrafNav version 8.1 (Waypoint Product Group). DGPS is a standard process for navigational accuracy either during acquisition or during post-processing.
  2. How accurate are the geographic locations?
    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 8.1 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 0.00042 seconds latitude and 0.00096 seconds longitude for TMRK and 0.00036 seconds latitude and 0.00047 seconds longitude for BERM.
  3. How accurate are the heights or depths?
    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 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 deferentially corrected navigation files; base station GPS processed to boat GPS; were exported from GrafNav and then imported into CARIS HIPS and SIPS and 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% of the 653 crossings. The maximum vertical transformation error (ellipsoid to orthometric heights or tidal datums) reported by VDatum for eastern Louisiana is 17.1 centimeters.
  4. Where are the gaps in the data? What is missing?
    These are complete post-processed xyz bathymetric data points from acoustic single-beam data collected in July 2012 from the northern Chandeleur Islands.
  5. How consistent are the relationships among the observations, including topology?
    This file represents the post-processed bathymetric data (x,y,z)collected during a single-beam bathymetry survey. They represent data coverage for the single-beam portion of the 2012 Chandeleur survey, specifically Field Activity Number (FAN) 12BIM04. Refer to the online data series linkage for field logs, vessel platform descriptions, and other survey information; this information is directly available at http://pubs.usgs.gov/ds/847

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints:
The U.S. Geological Survey requests that it be referenced as the originator of this dataset in any future products or research derived from these data.
Use_Constraints:
The U.S. Geological Survey requests that it be referenced as the originator of this dataset in any future products or research derived from these data. These data should not be used for navigational purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    Nancy T. DeWitt
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
  2. What's the catalog number I need to order this data set? Downloadable Data File Name
  3. What legal disclaimers am I supposed to read?
    This DVD 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?
  5. What hardware or software do I need in order to use the data set?
    The ASCII text files contained in the .zip archive can be accessed with any standard text file reader.

Who wrote the metadata?

Dates:
Last modified: 20-Mar-2019
Metadata author:
Nancy T. DeWitt
U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
Geologist
600 4th Street South
St. Petersburg, FL
USA

(727) 502-8000 (voice)
ndewitt@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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