Single-Beam Bathymetric Data Collected in 2011 from the Chandeleur Islands, Louisiana (U.S. Geological Survey Field Activity Number 11BIM02)

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What does this data set describe?

Title:
Single-Beam Bathymetric Data Collected in 2011 from the Chandeleur Islands, Louisiana (U.S. Geological Survey Field Activity Number 11BIM02)
Abstract:
As part of the Barrier Island Evolution Research Project, scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys off the northern Chandeleur Islands, Louisiana, in June of 2011. The overall objectives of the study are 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). 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 three 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 11BIM01 and 11BIM02) along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge, Louisiana, in June of 2011. 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 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, 20131231, Single-Beam Bathymetric Data Collected in 2011 from the Chandeleur Islands, Louisiana (U.S. Geological Survey Field Activity Number 11BIM02):.

    Online Links:

    This is part of the following larger work.

    DeWitt, Nancy T., Pfeiffer, William R., Bernier, Julie C., Buster, Noreen, Miselis, Jennifer L., Flocks, James G., Reynolds, B.J., Wiese, Dana S., and Kelso, Kyle W., 20131231, Coastal Bathymetry Data Collected in 2011 from the Chandeleur Islands, Louisiana: U.S. Geological Survey Data Series 848, U.S. Geological Survey, St. Petersburg, Florida.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.90112
    East_Bounding_Coordinate: -88.761988
    North_Bounding_Coordinate: 30.070927
    South_Bounding_Coordinate: 29.86931
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 02-Jun-2011
    Ending_Date: 16-Jun-2011
    Currentness_Reference:
    ground condition
  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?
    11BIM01_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) geodetic datum. (Source: USGS)
    11BIM02_SBB_NAD83_NAVD88_G09_xyz.txt
    ASCII text file containing the processed single-beam bathymetry x,y,z point data transformed 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)
    11BIM02_SBB_WGS84_MLLW_xyz.txt
    ASCII text file containing the processed single-beam bathymetry x,y,z point data transformed to the World Geodetic Systmem of 1984 (WGS84 G1150; equivalent to ITRF00) geodetic datum and Mean Lower Low Water (MLLW) tidal datum. (Source: USGS)
    ITRF00_X
    ITRF00 x-coordinate (easting) of sample point, in meters (Source: SANDS)
    Range of values
    Minimum:316606.963
    Maximum:329964.074
    Units:meters
    Resolution:0.001
    ITRF00_Y
    ITRF00 y-coordinate (northing) of sample point, in meters (Source: SANDS)
    Range of values
    Minimum:3305647.893
    Maximum:3328026.891
    Units:meters
    Resolution:0.001
    ITRF00_Z
    ITRF00 ellipsoid height of sample point, in meters (Source: SANDS)
    Range of values
    Minimum:-41.633
    Maximum:-28.446
    Units:meters
    Resolution:0.001
    DataType
    Geophysical data type (Source: USGS)
    ValueDefinition
    SBBSingle-beam bathymetry
    Year
    Year data was collected (Source: USGS) Character string
    Lon_ITRF00
    ITRF00 longitude of sample point, in decimal degrees (Source: VDatum)
    Range of values
    Minimum:-88.901128
    Maximum:-88.761996
    Units:decimal degrees
    Resolution:0.00001
    Lat_ITRF00
    ITRF00 latitude of sample point, in decimal degrees (Source: VDatum)
    Range of values
    Minimum:29.869315
    Maximum:30.070932
    Units:meters
    Resolution:0.00001
    NAD83_X
    NAD83 x-coordinate (easting) of sample point, in meters (Source: VDatum)
    Range of values
    Minimum:316607.6835
    Maximum:329964.7914
    Units:meters
    Resolution:0.001
    NAD83_Y
    NAD83 y-coordinate (northing) of sample point, in meters (Source: VDatum)
    Range of values
    Minimum:3305647.3048
    Maximum:3328026.2979
    Units:meters
    Resolution:0.001
    NAVD88_G09
    NAVD88 GEOID09 orthometric height of sample point, in meters (Source: VDatum)
    Range of values
    Minimum:-13.7002
    Maximum:-0.5483
    Units:meters
    Resolution:0.001
    Lon_NAD83
    NAD83 longitude of sample point, in decimal degrees (Source: VDatum)
    Range of values
    Minimum:-88.901120
    Maximum:-88.761988
    Units:decimal degrees
    Resolution:0.00001
    Lat_NAD83
    NAD83 latitude of sample point, in decimal degrees (Source: VDatum)
    Range of values
    Minimum:29.869310
    Maximum:30.070927
    Units:meters
    Resolution:0.00001
    Lon_WGS84
    WGS84 (G1150) longitude of sample point, in decimal degrees (Source: VDatum)
    Range of values
    Minimum:-88.901128
    Maximum:-88.761996
    Units:decimal degrees
    Resolution:0.00001
    Lat_WGS84
    WGS84 (G1150) latitude of sample point, in decimal degrees (Source: VDatum)
    Range of values
    Minimum:29.869315
    Maximum:30.070932
    Units:meters
    Resolution:0.00001
    MLLW
    MLLW tidal elevation of sample point, in meters (Source: VDatum)
    Range of values
    Minimum:-13.7002
    Maximum:-0.5483
    Units:meters
    Resolution:0.001

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?
    U.S. Geological Survey
    Attn: Nancy DeWitt
    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 the output of processed single beam bathymetry data collected in June 2011 around the northern 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: 16-Jun-2011 (process 1 of 6)
    GPS Acquisition: A GPS base station was erected at a temporarily installed USGS benchmark (TMRK) located on the sound side of the Chandeleur Islands within about 15 km of the farthest single-beam trackline. GPS receivers recorded the 12-channel full-carrier-phase positioning signals (L1/L2) from satellites via the Thales choke-ring antenna. This GPS instrument combination was duplicated on the survey vessel (rover). The base receiver and the rover receiver record their positions concurrently at 1-second (s) recording intervals throughout the survey. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Date: 16-Jun-2011 (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, 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 Marimatech E-SEA-206 echosounder system with dual 208-kilohertz (kHz) transducers. 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:
    U.S. Geological Survey
    Attn: Nancy DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Date: 01-Mar-2012 (process 3 of 6)
    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 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 the trajectories between the base to 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 the World Geodetic System of 1984 (WGS84) (G1150) geodetic datum. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Date: 01-Jun-2012 (process 4 of 6)
    Single-beam Bathymetry Processing: The final DGPS positions exported from GrafNav were merged with the raw HYPACK files using the System for Accurate Nearshore Depth Surveying (SANDS), version 3.2. SANDS is a single-beam acoustic (sounding) GPS-based hydrographic processing software developed by the USGS for shallow water bathymetric mapping. Data were merged, geometrically corrected, and exported from SANDS in the originally acquired ellipsoid datum of WGS84 (G1150), which is equivalent to ITRF00. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Data sources produced in this process:
    • 11BIM02_SBB_ITRF00_xyz.txt
    Date: 01-Jun-2012 (process 5 of 6)
    Single-Beam Bathymetry Error Analysis: The processed single-beam data points were imported into ArcGIS, and an in-house Python script was created to evaluate the elevation differences at the intersection of crossing tracklines. The script calculates the elevation difference between points at each intersection using an inverse distance weighting equation. Elevation values at line crossings should not differ by more than the combined instrument acquisition error (manufacturer specified accuracies). GPS cycle slips, stormy weather conditions, and rough sea surface states may all contribute to poor data quality. If discrepancies were found that exceed the acceptable error threshold, then the line determined to be in error was either statically adjusted or removed. A line in error is considered to have one or more of the following: (1) a segment where several crossings are incomparable, (2) a known equipment problem, or (3) known bad GPS data seen in the post-processing steps. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Date: 28-Apr-2013 (process 6 of 6)
    Datum transformation: Using the transformation software VDatum version 3.2, both the single-beam bathymetric x,y,z data were transformed horizontally from their data acquisition 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 elevation and Mean Lower Low Water (MLLW) tidal datum using the National Geodetic Survey (NGS) geoid model of 2009 (GEOID09). Person who carried out this activity:
    U.S. Geological Survey
    Attn: Nancy DeWitt
    Geologist
    600 4th Street South
    St. Petersburg, FL
    USA

    (727) 502-8000 (voice)
    ndewitt@usgs.gov
    Data sources produced in this process:
    • 11BIM02_SBB_NAD83_NAVD88_GEOID09_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 the 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 Marimatech 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 8.10). GPS 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.
  2. How accurate are the geographic locations?
    All static GPS base station sessions were run 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 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 weighted value of occupation time was calculated for each day (longer occupation times held more value than shorter times). The final value for latitude, longitude, and ellipsoid was a weighted average of all the GPS session. This value was then used in GrafNav 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. For this survey, the maximum horizontal error for the base station used for processing the single-beam bathymetry was 0.00000 to 0.00018 decimal seconds for latitude and 0.00002 to 0.00045 decimal seconds in longitude.
  3. How accurate are the heights or depths?
    All static base station sessions 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. For this survey, the maximum vertical error for the base station used for processing the single-beam bathymetry was +/- 2.1 cm. All single-beam soundings are post-processed to the base station coordinates. During acquisition ship motion was measured using a TSS DMS-05 sensor which measures roll, pitch (manufacturer's specified accuracy +/- 0.05 degrees), and heave (5 percent of heave amplitude or 5 cm). During processing, the TSS measurements were used to geometrically correct the differentially corrected sounding positions. For the single-beam soundings, elevation differences at all trackline crossings were less than or equal to 14 cm, and the elevation differences were within +/- 10 cm for 99.3% of the 434 crossings at which the horizontal distance between soundings was less than 2 m. The maximum vertical transformation error 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 x,y,z bathymetric data points from acoustic single-beam data collected in June 2011 from around the northern Chandeleur Islands.
  5. How consistent are the relationships among the observations, including topology?
    This zip archive contains the post-processed single-beam bathymetric data from a single research cruise in June 2011. Refer to the online data series linkage for field logs, vessel platform descriptions, and other survey information.

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)
    U.S. Geological Survey
    Attn: Nancy DeWitt
    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
  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 have been 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: 08-Jun-2016
Metadata author:
U.S. Geological Survey
Attn: Nancy DeWitt
Geologist
600 4th Street South
St. Petersburg, FL
USA

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

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