Bathymetric Survey of the Nearshore from Belle Pass to Caminada Pass, Louisiana: Methods and Data Report

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Frequently anticipated questions:

What does this data set describe?

Bathymetric Survey of the Nearshore from Belle Pass to Caminada Pass, Louisiana: Methods and Data Report
The U.S. Geological Survey (USGS), in cooperation with the University of New Orleans (UNO) and the Louisiana Department of Natural Resources (LDNR), conducted a high-resolution, single-beam bathymetric survey along the southern Louisiana coastal zone from Belle Pass to Caminada Pass. The survey consisted of 483 line-kilometers of data acquired in July and August of 2005. This report outlines the methodology and provides the data from the survey. Analysis of the data and comparison to a similar bathymetric survey completed in 1989 show significant loss of seafloor and shoreline retreat, which is consistent with previously published estimates of shoreline change in the study area.
  1. How might this data set be cited?
    DeWitt, Nancy T., James, G. Flocks, Hansen, Mark, Kulp, Mark, and Reynolds, B.J., 2007, Bathymetric Survey of the Nearshore from Belle Pass to Caminada Pass, Louisiana: Methods and Data Report: U. S. Geological Survey Data Series 312, CD-ROM.

    DeWitt, N.T., Flocks, J. G., Hansen, Mark, Kulp, Mark, Reynolds, B.J., 2007, Bathymetric Survey of the Nearshore from Belle Pass to Caminada Pass, Louisiana: Methods and Data Report: U.S. Geological Survey Data Series 312 CD-ROM. Also available online at <>
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -90.228836
    East_Bounding_Coordinate: -89.995983
    North_Bounding_Coordinate: 29.199592
    South_Bounding_Coordinate: 29.009837
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 01-Jul-2005
    Ending_Date: 01-Sep-2005
    publication date
  5. What is the general form of this data set?
  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?
      The horizontal datum used is North American Datum of 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 1/298.25722210100002.
  7. How does the data set describe geographic features?
    Point Data
    Text Delimited File (Source: CSV)
    Easting (Source: UTM Zone 15)
    Range of values
    Northing (Source: UTM Zone 15)
    Range of values
    elevation to NAVD88 (Source: NAVD88)
    Range of values
    track line name as named by HYPACK Software (Source: HYPACK version 4.3)
    Formal codeset
    Codeset Name:###_####
    Codeset Source:First 3 numbers represent the number of the line and the last 4 numbers represent the time at which the line was aquired.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Nancy T. DeWitt
    • James, G. Flocks
    • Mark Hansen
    • Mark Kulp
    • B.J. Reynolds
  2. Who also contributed to the data set?
    We would like to thank UNO and the LDNR for their partnership on this project.
  3. To whom should users address questions about the data?
    Nancy T. DeWitt
    Marine Geologist
    600 4th Street South
    St. Petersburg, FL

    727-803-8747 x3058 (voice)
    727-803-2030 (FAX)

Why was the data set created?

This project is a collection of high-resolution single-beam modern bathymetry data along the rapidly retreating Caminada-Moreau headland in the southern coastal zone, Louisiana, from Belle Pass eastward to Caminada Pass. These bathymetric data provide a 2005 dataset which succeeds a portion of the Louisiana Barrier Island Erosion Study: Atlas of Sea-Floor Changes from 1878 to 1989 by List and others (1994). The survey lines from Belle Pass to Caminada Pass (page 15 of the 1994 atlas) were digitized and resurveyed in 2005 in efforts to report sediment distribution (loss/gain) and shoreline transgression/regression along the Caminada-Moreau headland since the 1989 surveys.

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: 01-Jan-2005 through 20061231 (process 1 of 1)
    Points containing x, y, and z (latitude, longitude, and depth) data are collected through a USGS-developed surveying system, the System for Accurate Nearshore Depth Surveying (SANDS). The SANDS system consists of a shallow draft boat equipped with two Ashtech Z-Xtreme GPS receivers which acquire full-phase-carrier signals from the NAVSTAR GPS constellation. The USGS SANDS utilizes Ashtech Z-Xtreme dual frequency, 12-channel full-carrier-phase GPS receivers. Dorne-Margolin type choke ring antennas are used at the reference station and on the boat. GPS acquisition interval is 1second (1 hertz). To minimize the adverse effects of vessel motion, the SANDS system is equipped with a TSS-DMS-05 heave, pitch, and roll compensator. Motion acquisition interval is 0.05 seconds (20 hertz). The scientific grade echosounder or fathometer used in the SANDS system is a Marimatech E-SEA-103. Sounding acquisition interval is 0.1 seconds (10 hertz). The boat is navigated and all sensor data acquired using Coastal Oceanographics Inc. HYPACK surveying software. The GPS data from the reference point (base station) and the GPS data from the boat (rover) are processed together using Waypoint Consulting, Inc., GrafNav GPS processing software, which produces the differential navigation file for the survey session. The USGS SANDS software merges this differential navigation file with all senor data based upon time, performs geometric corrections, and outputs final x, y, z data relative to NAVD88 via GEOID03. The x, y, z data are then imported into CPS-3 Software by Schlumberger and gridded at 135 grid node spacing. This grid node spacing corresponds with the gridded datasets from the 1980s survey outlined in List and others (1994). Person who carried out this activity:
    Nancy T. DeWitt
    Marine Geologist
    600 4th Street South
    St. Petersburg, FL

    727-803-8747 x3058 (voice)
    727-803-2030 (FAX)
  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 attributes (latitude, longitude, and depth) is dependent on the accuracies of the equipment used to measure their values. See horizontal and vertical positional accuracy for further information.
  2. How accurate are the geographic locations?
    The accuracy of the horizontal positions (latitude and longitude) is based on the accuracy of the Ashtech dual-channel (Z-Xtreme), full-carrier-phase resolving geodetic differential GPS receivers.
  3. How accurate are the heights or depths?
    The accuracy of the vertical position is based on the accuracy of the Ashtech dual-channel (Z-Xtreme), full-carrier-phase resolving geodetic differential GPS receivers.
  4. Where are the gaps in the data? What is missing?
    Data are complete. Surveys are conducted only during optimal weather conditions (surveying is not performed during storms or when winds are above 15 knots). Weather conditions, such as heavy storms, lightning storms, and heavy cloud cover, and water clarity affect the collection process. Surveying was halted when GPS cycle slips occurred or when Percent Dilution of Position (PDOP) values were greater than 3.0. These weather problems result in poor or inaccurate readings from the GPS unit. Any questionable data points are removed or reprocessed through the GPS processing software.
  5. How consistent are the relationships among the observations, including topology?
    A fixed 1-meter bar is used for calibrating the USGS fathometer for shallow water surveys. The 1-meter bar is sufficient, as most shallow water surveys are conducted in 3 meters of water or less, and a very accurate bar check is mandated. The USGS bar is attached to the boat directly below the transducers. The USGS bar consists of a 1.5-inch aluminum pipe connected horizontally to a flat plate which is anchored to the boat. Because of the short bar length, this check only accounts for index errors of the echo system and does not account for speed-of-sound variations with depth. In shallow water surveys the high sound velocity to depth ratio and the assumed mixing of the water tend to decrease the significance of sound velocity variations due to salinity and temperature gradients in the water column. For these reasons, using an average sound velocity of 1,500 meters per second (m/s) in combination with the daily bar check is suitable within the depth range of surveying. Full-phase-carrier GPS data are acquired simultaneously by the reference and boat receivers. Reference station GPS data are first used to derive reference station coordinates (latitude, longitude, elevation) and later used for kinematic processing of the boat GPS data. All kinematic data processing for this study were processed using GrafNav software by Waypoint, Inc. This processing step produces an accurate boat position and elevation at 1-second intervals, or about 10 feet (3 meters) apart along a track line.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Any use of these data signifies a user's agreement to insure all portions of the metadata are read and clearly understood before using these data in order to protect both user and the USGS interest.
Acknowledgment of the USGS, Florida Integrated Science Center (FISC), St. Petersburg, FL, and the University of New Orleans, Department of Earth and Environmental Sciences, New Orleans, LA, as the source for the data would be appreciated in products developed from these data and such acknowledgements as is standard for citation and legal practices for data source is expected by users of this data. Users should be aware of comparisons with other datasets for the same area from other time periods which may be inaccurate due to inconsistencies resulting from different collection procedures, mapping procedures and lab or computer analysis. Although the USGS is making these datasets available to others who may find the data of value, USGS does not warrant, endorse, or recommend the use of this data for any given reason.
  1. Who distributes the data set? (Distributor 1 of 1)
    Nancy T. DeWitt
    Marine Geologist
    600 4th Street South
    St. Petersburg, FL

    727-803-8747 x3058 (voice)
    727-803-2030 (FAX)
  2. What's the catalog number I need to order this data set? Digital Data
  3. What legal disclaimers am I supposed to read?
    THIS INFORMATION IS DISTRIBUTED SOLELY FOR THE PURPOSE OF PREDISSEMINATION PEER REVIEW UNDER APPLICABLE INFORMATION QUALITY GUIDELINES. IT HAS NOT BEEN DISSEMINATED BY USGS. IT DOES NOT REPRESENT AND SHOULD NOT BE CONSTRUED TO REPRESENT ANY DETERMINATION OR POLICY OF THE DEPARTMENT OF THE INTERIOR. Although these data have been processed successfully on a computer system at the designated principal investigator's facility, no warranty expressed or implied is made regarding the accuracy or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data or aggregate use with other data. It is strongly recommended that these data are directly acquired from the official USGS integrated science data server or from the principal investigator and not indirectly through other sources which may have changed the data in some way. It is also strongly recommended that careful attention be given to the contents of the metadata file associated with these data. The Principal investigator shall not be held liable for improper or incorrect use of the data described and (or) contained herein. So, these data are provided as is and without any expressed or implied warranties. In addition, use of trade names or commercial products in the metadata file is solely for providing specific information, and does not imply recommendation or endorsement. Any downloading and use of these data signifies a user's agreement to comprehension and compliance of the disclaimer. Insure all portions of the metadata are read and clearly understood before using the data in order to protect both user and principal investigator's interests.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: Point data file in format CSV (version CSV) Text delimited file Size: 5.5 MB
      Network links:
      Media you can order: CD-ROM (format CD-RW)
    • Cost to order the data: none

Who wrote the metadata?

Last modified: 15-Dec-2006
Last Reviewed: 16-May-2007
Metadata author:
Nancy T. DeWitt
Marine Geologist
600 4th St. South
St. Peterbsurg, FL

727-803-8747 x3058 (voice)
727-803-2030 (FAX)
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

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