tmunro_1m_bathycontours_MLLW.shp - 1-meter contours produced from swath bathymetry collected by the U.S. Geological Survey in Woods Hole, MA and St. Petersburg, FL offshore of the Gulf Islands, MS, 2010 (ESRI polyline shapefile)

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Frequently-anticipated questions:

What does this data set describe?

Title:
tmunro_1m_bathycontours_MLLW.shp - 1-meter contours produced from swath bathymetry collected by the U.S. Geological Survey in Woods Hole, MA and St. Petersburg, FL offshore of the Gulf Islands, MS, 2010 (ESRI polyline shapefile)
Abstract:
In 2010, the U.S. Geological Survey in Woods Hole, MA and St. Petersburg, FL, in partnership with the U.S. Army Corps of Engineers, Mobile District conducted geologic mapping to characterize the seafloor and shallow subsurface stratigraphy offshore of the Gulf Islands of Mississippi. The mapping was carried out during two cruises in March, 2010 on the R/V Tommy Munro of Biloxi, MS. Data were acquired with the following equipment: an SEA Ltd SwathPlus interferometric sonar (both 234 kHz and 468 kHz systems), a Klein 3000 and a Klein 3900 dual frequency sidescan-sonar, and an Edgetech 512i chirp subbottom profiling system. The long-term goal of this mapping effort is to produce high-quality, high-resolution geologic maps and geophysical interpretations that can be utilized to identify sand resources within the region and better understand the Holocene evolution and anticipate future changes in this coastal system. More information on the field work can be accessed from the Woods Hole Coastal and Marine Science Center Field Activity webpage <http://quashnet.er.usgs.gov/data/2010/10012/> or the St. Petersburg Coastal and Marine Geology InfoBank <http://walrus.wr.usgs.gov/infobank/m/m210gm/html/m-2-10-gm.meta.html>.
  1. How should this data set be cited?

    U.S. Geological Survey, 2011, tmunro_1m_bathycontours_MLLW.shp - 1-meter contours produced from swath bathymetry collected by the U.S. Geological Survey in Woods Hole, MA and St. Petersburg, FL offshore of the Gulf Islands, MS, 2010 (ESRI polyline shapefile): Open-File Report 2010-1178, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Pendleton, Elizabeth A. , Baldwin, Wayne E. , Danforth, William W. , Dewitt, Nancy T. , Forde, Arnell S. , Foster, David S. , Kelso, Kyle W. , Pfeiffer, William R. , Turecek, Aaron M. , Flocks, James G. , and Twichell, David C. , 2011, Geophysical Data from offshore of the Gulf Islands National Seashore, Cat Island to Western Horn Island, Mississippi: Open-File Report 2010-1178, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -89.074059
    East_Bounding_Coordinate: -88.638553
    North_Bounding_Coordinate: 30.227424
    South_Bounding_Coordinate: 30.127676

  3. What does it look like?

    <https://pubs.usgs.gov/of/2010/1178/GIS_catalog/Bathy/bathy_cntr.png> (PNG)
    1-m swath bathymetric contours offshore of the Gulf Islands, MS

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 04-Mar-2010
    Ending_Date: 29-Mar-2010
    Currentness_Reference:
    Data were not collected on 20100310, 20100312-20100314, 20100318, and 20100321-20100326 due to weather conditions, crew changes, or survey location.

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: vector digital data

  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?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000001. Longitudes are given to the nearest 0.000001. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.

      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: Mean lower low water
      Depth_Resolution: 0.1 meters
      Depth_Distance_Units: meters
      Depth_Encoding_Method: attribute values

  7. How does the data set describe geographic features?

    tmunro_1m_bathyconturs_MLLW
    1-m bathymetric contours (Source: U.S. Geological Survey)

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Shape
    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    CONTOUR
    water depth (Source: U.S. Geological Survey)

    Range of values
    Minimum:-13
    Maximum:-4
    Units:meters
    Resolution:1.0

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

  3. To whom should users address questions about the data?

    David C. Twichell
    U.S. Geological Survey
    Oceanographer
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700x2266 (voice)
    (508) 457-2310 (FAX)
    dtwichell@usgs.gov

Why was the data set created?

This shapefile represents 1-meter interval bathymetric contours of swath data that were collected in 2010. These data are used to define the sea-floor morphology offshore of the Gulf Islands in Mississippi.

How was the data set created?

  1. From what previous works were the data drawn?

    (source 1 of 1)
    U.S. Geological Survey.

    Type_of_Source_Media: disc
    Source_Contribution:
    Swath data acquisition at sea (2010): These bathymetric data were collected with 2 SEA Ltd Swathplus interferometric sonars (a 234 kHz and a 468 kHz system) mounted on the portside of the R/V Tommy Munro of Biloxi, MS. The WHCMSC acquired data with the 234 kHz system between March 4, 2010 and March 17, 2010. The St. Petersburg Coastal and Marine Science Center acquired data with the 468 kHz system between March 19, 2010 and March 29, 2010. All data were acquired with SwathPlus Software (version: 3.6.5). Tracklines are spaced 150 m apart in the shore parallel direction.

  2. How were the data generated, processed, and modified?

    Date: 2010 (process 1 of 5)
    SwathPlus Software (version: 3.7.0) was used to acquire the raw swath data (*.sxr) and output a processed soundings file (*.sxp). Several bathy filters were applied to the processed file within SwathPlus to remove erroneous soundings and reduce the density of the data. Corrections were also applied for speed of sound changes (using sound velocity profiles), ship motion, GPS antennae offsets, and transducer depth and angle below the surface. Bathy filters included a low amplitude (100), range (1-m below the surface), box (2-m to avoid nadir), alongtrack 1 (depth difference of 10-m, window size 10-m, and learn rate of 0.6), alongtrack 2 (depth difference of 1-m, window size 1-m, and learn rate of 0.9), and a mean filter (0.1-m).

    Person who carried out this activity:

    Elizabeth A. Pendleton
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700x2259 (voice)
    (508) 457-2310 (FAX)
    ependleton@usgs.gov

    Date: 2010 (process 2 of 5)
    CARIS (version: HIPS and SIPS 6.1; service pack 2) was used to import the processed bathy files (*.sxp) from SwathPlus format to CARIS HDCS data format using the conversion utility. The data were corrected for errors in soundings due to additional sound refraction not accounted for by sound velocity profiles using the CARIS refraction editor. These artifacts can be recognized in a cross-swath profile of a relatively flat patch of sea floor. When viewing the swath data across a profile, the sea floor will appear to have a "frown" or "smile" when in fact the data should be flat across the profile. Insufficient and/or erroneous sound velocity information, which is usually due to too widely spaced or non-existent velocity profiles within an area, results in an under or over-estimate of water depth which increases with distance from the center of the swath. The bathymetric data were also corrected to mean lower low water (MLLW) using a discrete tidal-zoning model (DTZ) developed by NOAA/NOS's Hydrographic Planning Team (Huang, personal communication, 2010) (<http://www.tidesandcurrents.noaa.gov/hydro.html>). The DTZ model corrects differences in tidal phase and amplitude between the survey area and observations made at NOS tide gauges at Gulfport Harbor (8745557) and Pascagoula NOAA Lab (8741533). The tidal zone models were imported into CARIS (version: HIPS and SIPS 6.1) as text files and used to correct tidal observations for each survey. Once the tidal zone model was imported into CARIS using the tide editor, the tidal range and phase offsets were applied and remerged in CARIS(version: HIPS and SIPS 6.1), making all the soundings relative to MLLW. A 5-meter base surface of tide corrected bathymetric soundings was created in CARIS, then exported as ASCII x,y,z data.

    Person who carried out this activity:

    Elizabeth A. Pendleton
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700x2259 (voice)
    (508) 457-2310 (FAX)
    ependleton@usgs.gov

    Date: 2010 (process 3 of 5)
    The 5-m ASCII x,y,z file (for each cruise; St. Pete and WHCMSC) was gridded in GMT (version: 4.2.1; Wessel and Smith, 1998) using 'blockmedian' with a cell size of 50 meters. This routine was conducted to minimize edge effects in the 'surface' gridding routine because these data were collected at approximately 40-50% seafloor coverage. Next a tension spline routine (at 0.1) in GMT was used ('surface') to create a netCDF grid.

    Person who carried out this activity:

    Elizabeth A. Pendleton
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700 x2259 (voice)
    (508) 457-2310 (FAX)
    ependleton@usgs.gov

    Date: 12-Aug-2010 (process 4 of 5)
    The GMT grid (*.grd) was then converted to an ESRI Binary Grid via Mirone (version 1.5.0; Luis, 2007) and MATLAB R2007b (version 7.5.0.342) - save grid as - ArcGIS binary grid. The projection was defined in ArcMap (version: 9.3) using Data Management Tools - Projections and Transformations - Define Projection: UTM, zone 16N, WGS84 Datum. This grid was then reprojected with ArcToolbox (Data Management Tools - Projections and Transformations - Raster - Project Raster) to create a grid in geographic coordinate system WGS84.

    Person who carried out this activity:

    Elizabeth A. Pendleton
    U.S. Geological Survey
    Geologist
    U.S. Geological Survey
    Woods Hole, MA 02543

    (508)-548-8700 x2259 (voice)
    (508)-457-2310 (FAX)
    ependleton@usgs.gov

    Date: 2010 (process 5 of 5)
    A shapefile containing 1-meter interval contours was then created using Xtools Pro (version 5.2.0; build 482) for ArcGIS (version: 9.3; build 1850): Surface Tools - Convert grid to Contours using a base contour of -13. The bounding contour was deleted.

    Person who carried out this activity:

    Elizabeth A. Pendleton
    U.S. Geological Survey
    Geologist
    U.S. Geological Survey
    Woods Hole, MA 02543
    USA

    (508)-548-8700 x2259 (voice)
    (508)-457-2310 (FAX)

  3. What similar or related data should the user be aware of?

    Huang, Lijuan, 20100226, NOAA/NOS Hydrographic Planning Team (HPT) tide zone model.

    Online Links:

    Luis, J. F. , 2007, Mirone: A multi-purpose tool for exploring grid data.: Computers and Geosciences 33, Elsevier, Amsterdam.

    Online Links:

    Wessel, P., and Smith, W.H.F., 1998, New, improved version of the Generic Mapping Tools released: EOS Transactions 79, American Geophysical Union, Washington, DC.

    Online Links:

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

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

    These data were navigated with a Differential Global Positioning System (DGPS); they are accurate to +/- 1 to 2 meters, horizontally. Unless noted, all DGPS data are referenced to WGS84, and distance between sidemounted interferometric sonar and GPS antennae are corrected.

  3. How accurate are the heights or depths?

    The theoretical vertical resolution of the SEA Ltd SwathPlus interferometric sonar is 1 % of water depth, approximately 0.1 m within the study area. An Octopus F180 Attitude and Positioning system was used to correct for vessel roll, pitch, heave, and yaw during the first leg, 2010-012FA, whereas an Octopus F190 Attitude and Positioning system was used during the second leg, 10cct02. Tidal offsets were corrected with a NOAA tide zone model and referenced to mean lower low water (MLLW). Errors associated with the tidal zone model could be less than or equal to the tidal range for this area which is ~0.4 m. The gridding algorithm and cell size used on these data could introduce errors as great as 3 m along the edges of the Gulfport Ship Channel. Gridding-induced errors are likely much smaller (< 0.5 m) for most of the study area where slopes are less than 1 degree. Changes in ship draft due to water and fuel usage were not considered.

  4. Where are the gaps in the data? What is missing?

    All shore parallel survey lines were incorporated. Tie (shore perpendicular) lines were not used in grid generation. The R/V Tommy Munro was contracted for the month of March 2010. The Woods Hole Coastal and Marine Science Center acquired data onboard between March 4 and March 17, 2010. Bathy data were acquired on 20100304-20100309; 20100311;20100315-20100317. Day gaps in acquisition were due to inclement weather or seismic tieline acquisition. The St. Petersburg Coastal and Marine Science Center acquired data onboard the R/V Tommy Munro between March 19 and March 29, 2010. Bathy data for this dataset were acquired on 201003019-20100320; 20100327-2010329. Day gaps in acquisition were due to inclement weather or data acquisition in another survey area.

  5. How consistent are the relationships among the observations, including topology?

    Any spurious data points were removed during processing.

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:
Not to be used for navigation. The Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset.

  1. Who distributes the data set? (Distributor 1 of 1)

    Elizabeth A. Pendleton
    U.S. Geological Survey
    Geologist
    384 Woods Hole Rd.
    Woods Hole, MA 02543-1598

    (508) 548-8700x2259 (voice)
    (508) 457-2310 (FAX)
    ependleton@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?

    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    This zip file contains data available in Environmental Systems Research Institute (ESRI) polyline shapefile format. The user must have ArcGIS or ArcView 3.0 or greater software to read and process the data file. In lieu of ArcView or ArcGIS, the user may utilize another GIS application package capable of importing the data. A free data viewer, ArcExplorer, capable of displaying the data is available from ESRI at www.esri.com.

Who wrote the metadata?

Dates:
Last modified: 29-Apr-2011
Metadata author:
Elizabeth A. Pendleton
U.S. Geological Survey
Geologist
384 Woods Hole Road
Woods Hole, MA 02543-1598
USA

508-548-8700 x2259 (voice)
(508)-457-2310 (FAX)
ependleton@usgs.gov

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.8.14 on Fri Apr 29 14:59:38 2011