Contours--Offshore of Half Moon Bay, California

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Frequently anticipated questions:

What does this data set describe?

Title: Contours--Offshore of Half Moon Bay, California
Abstract:

This part of DS 781 presents data for the bathymetric contours for several seafloor maps of the Offshore of Half Moon map area, California. The vector data file is included in "Contours_OffshoreHalfMoonBay.zip," which is accessible from <https://pubs.usgs.gov/ds/781/OffshoreSanGregorio/data_catalog_OffshoreSanGregorio.html>.

10-m interval contours of the Offshore of Half Moon Bay map area, California, were generated from bathymetry data collected by Fugro Pelagos and by California State University, Monterey Bay, Seafloor Mapping Lab (CSUMB). Mapping was completed in 2006 and 2007, using a combination of 400-kHz Reson 7125 and 244-kHz Reson 8101 multibeam echosounders. These mapping missions combined to collect bathymetry from about the 10-m isobath to beyond the 3-nautical-mile limit of California's State Waters. Bathymetric contours at 10-m intervals were generated from the merged 2-m bathymetric surface. The most continuous contour segments were preserved while smaller segments and isolated island polygons were excluded from the final output. Contours were smoothed via a polynomial approximation with exponential kernel (PAEK) algorithm using a tolerance value of 60 m. The contours were then clipped to the boundary of the map area. These data are not intended for navigational purposes.
  1. How should this data set be cited?

    Bretz, Carrie K., Kvitek, Rikk G., Dartnell, Peter, and Phillips, Eleyne L., 2014, Contours--Offshore of Half Moon Bay, California:.

    This is part of the following larger work.

    Cochrane, Guy R., Dartnell, Peter, Greene, H. Gary, Johnson, Samuel Y., Golden, Nadine E., Hartwell, Stephen R., Dieter, Brian E., Mansion, Michael W., Sliter, Ray W., Ross, Stephanie L., Watt, Janet T., Endris, Charles A., Kvitek, Rikk G., Edwards, Brian D., Phillips, Eleyne L., Erdey, Mercedes D., Bretz, Carrie K., Chin, John L., and Bretz, Carrie K., 2014, California State Waters Map Series--Offshore of Half Moon Bay map area, California: Open-File Report OFR 2014-1214, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -122.58
    East_Bounding_Coordinate: -122.42
    North_Bounding_Coordinate: 37.55
    South_Bounding_Coordinate: 37.39

  3. What does it look like?

    <https://pubs.usgs.gov/ds/781/OffshoreHalfMoonBay/images/Contours_OffshoreHalfMoonBay.jpg> (JPEG)
    Contours derived from bathymetry of offshore Half Moon Bay.

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

    Beginning_Date: 2006
    Ending_Date: 2007
    Currentness_Reference: ground condition

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

    Geospatial_Data_Presentation_Form: vector

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • String

    2. What coordinate system is used to represent geographic features?

      The map projection used is WGS 1984 UTM Zone 10N.

      Projection parameters:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -123.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000.0
      False_Northing: 0.0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.0001
      Ordinates (y-coordinates) are specified to the nearest 0.0001
      Planar coordinates are specified in Meter

      The horizontal datum used is D WGS 1984.
      The ellipsoid used is WGS 1984.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.

  7. How does the data set describe geographic features?

    Contours_OffshoreHalfMoonBay.shp
    The shapefile attributes include FID - Internal Feature Number, SHAPE - feature geometry, VALUE - code for the seafloor character classes, ID - feature ID, and CONTOUR - contour depth value. The shapefile can be added to any ESRI ArcMap project. (Source: ESRI)

    FID
    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    SHAPE
    Feature geometry (Source: ESRI)

    Polyline

    ID
    Unique identifier for each contour line. Value of 0 means the line segment has been generated during the smoothing process. (Source: ESRI)

    Range of values
    Minimum:-50
    Maximum:-10
    Units:Double

    CONTOUR
    Contours are lines that connect points of equal depth based on the bathymetry grid. The contour values indicate the depth value the line represents. This makes it easier to identifier features on the seafloor. Contour lines were generated at 10-m intervals, from -10 m to -50 m, then the contours were clipped to the boundary of the map area. Values are negative to indicate depth below sea level. The value of 0 represents a line segment created during the smoothing process. (Source: USGS)

    Range of values
    Minimum:-50
    Maximum:-10
    Units:Integer values -10 to -50 representing depth intervals as described above.

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?

    Peter Dartnell
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Physical Scientist
    400 Natural Bridges Dr.
    Santa Cruz, CA 95060-5792
    USA

    (831) 460-7415 (voice)
    (831) 427-4709 (FAX)
    pdartnell@usgs.gov

Why was the data set created?

These data are intended for science researchers, students, policy makers, and the general public. This information is not intended for navigational purposes. These data can be used with geographic information systems or other software to identify bathymetric features.

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: 2007 (process 1 of 1)
    During the mapping missions, an Applanix position and motion compensation system (POS/MV) was used to accurately position the vessel during data collection, and it also accounted for vessel motion such as heave, pitch, and roll (position accuracy, +/-2 m; pitch, roll, and heading accuracy, +/-0.02 degrees; heave accuracy, +/-5 percent, or 5 cm). KGPS altitude data (Fugro Pelagos, StarFix HP & XP units; CSUMB, NavCom 2050) were used to account for tide cycle fluctuations and sound velocity profiles were collected with an Applied Microsystems SVPlus sound velocimeter. Soundings were corrected for vessel motion using the Applanix POS/MV data, for variations in water-column sound velocity using the AM SVPlus data, and for variations in water height (tides) using vertical-position data from the KGPS receivers. Final XYZ soundings and bathymetric-surface models were referenced to the World Geodetic System of 1984 (WGS 1984) relative to the North American Vertical Datum of 1988 (NAVD 1988). Bathymetric contours at 10-m intervals were generated from the merged 2-m bathymetric surface. The most continuous contour segments were preserved while smaller segments and isolated island polygons were excluded from the final output. Contours were smoothed via a polynomial approximation with exponential kernel (PAEK) algorithm using a tolerance value of 60 m. The contours were then clipped to the boundary of the map area.

    Person who carried out this activity:

    Carrie Bretz
    Seafloor Mapping Lab, California State University Monterey Bay
    Projects Manager, GIS & Metadata Supervisor
    100 Campus Center, Bldg 13
    Seaside, CA 93955
    USA

    831.582.4197 (voice)
    carrie_bretz@csumb.edu

  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?

    Not applicable

  2. How accurate are the geographic locations?

    Estimated to be no less than 2 m, owing to water depth and total propagated uncertainties of the mapping systems, which include sonar system, position and motion compensation system, and navigation, as well as data processing that includes sounding cleaning, gridding, and datum transformations.

  3. How accurate are the heights or depths?

    Estimated to be no less than 20 cm, owing to water depth and total propagated uncertainties of the mapping systems, which include sonar system, position and motion compensation system, and navigation, as well as data processing that includes sounding cleaning, gridding, and datum transformations.

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

    Complete

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

    Unspecified

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:

Please recognize the U.S. Geological Survey (USGS) and the California State University, Monterey Bay, Seafloor Mapping Lab (CSUMB). USGS-authored or produced data and information are in the public domain. This information is not intended for navigational purposes.
Read and fully comprehend the metadata prior to data use. Uses of these data should not violate the spatial resolution of the data.
Where these data are used in combination with other data of different resolution, the resolution of the combined output will be limited by the lowest resolution of all the data.
Acknowledge the U.S. Geological Survey in products derived from these data. Share data products developed using these data with the U.S. Geological Survey.
This database has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.
Although this Federal Geographic Data Committee-compliant metadata file is intended to document these data in nonproprietary form, as well as in ArcInfo format, this metadata file may include some ArcInfo-specific terminology.

Who wrote the metadata?

Dates:
Last modified: 17-Jun-2013
Last Reviewed: 25-Aug-2014
Metadata author:
Peter Dartnell
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Physical Scientist
400 Natural Bridges Dr.
Santa Cruz, CA 95060-5792
USA

(831) 460-7415 (voice)
(831) 427-4709 (FAX)
pdartnell@usgs.gov

Metadata standard:
Content Standard for Digital Geospatial Metadata ("CSDGM version 2") (FGDC-STD-001-1998)

Generated by mp version 2.9.16 on Wed Jan 21 17:04:42 2015