Digital elevation models (DEMs) of northern Monterey Bay, California, March 2015

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Frequently anticipated questions:


What does this data set describe?

Title:
Digital elevation models (DEMs) of northern Monterey Bay, California, March 2015
Abstract:
This part of the data release presents digital elevation models (DEMs) derived from bathymetry and topography data of northern Monterey Bay, California collected in March 2015. Bathymetry data were collected using two personal watercraft (PWCs), each equipped with single-beam echosounders and survey-grade global navigation satellite system (GNSS) receivers. Topography data were collected on foot with GNSS receivers mounted on backpacks and with an all-terrain vehicle (ATV) using a GNSS receiver mounted at a measured height above the ground. Additional topography data were collected with a terrestrial lidar scanner. DEM surfaces were produced from all available elevation data using linear interpolation.
Supplemental_Information:
Additional information about the field activities from which these data were derived are available online at:
http://cmgds.marine.usgs.gov/fan_info.php?fan=2015-625-FA
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. How might this data set be cited?
    Stevens, Andrew W., Logan, Joshua B., Snyder, Alexander G., and Hoover, Daniel J., 2017, Digital elevation models (DEMs) of northern Monterey Bay, California, March 2015: data release DOI:10.5066/F76H4GCW, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Stevens, Andrew W., Logan, Joshua B., Snyder, Alexander G., Hoover, Daniel J., Barnard, Patrick L., and Warrick, Jonathan A., 2017, Beach topography and nearshore bathymetry of northern Monterey Bay, California: data release DOI:10.5066/F76H4GCW, U.S. Geological Survey, Santa Cruz, CA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.025925
    East_Bounding_Coordinate: -121.788009
    North_Bounding_Coordinate: 36.978804
    South_Bounding_Coordinate: 36.807323
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/59e0e81ae4b05fe04cd00001?name=mb15_mar_dems_overall.png&allowOpen=true (PNG)
    image map showing overview of digital elevation models (DEMs) of northern Monterey Bay, color-coded to show elevation
    https://www.sciencebase.gov/catalog/file/get/59e0e81ae4b05fe04cd00001?name=mb15_mar_dems_inset.png&allowOpen=true (PNG)
    four zoomed-in image maps showing digital elevation models (DEMs) for (A) Santa Cruz, (B) Soquel Cove, (C) Manresa, and (D) Moss Landing areas of northern Monterey Bay, color-coded to show elevation
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 16-Mar-2015
    Ending_Date: 20-Mar-2015
    Currentness_Reference:
    ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: Esri ARC/INFO ASCII GRID
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Raster data set.
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 10
      Transverse_Mercator:
      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 row and column
      Abscissae (x-coordinates) are specified to the nearest 2
      Ordinates (y-coordinates) are specified to the nearest 2
      Planar coordinates are specified in Meter
      The horizontal datum used is NAD83 (2011).
      The ellipsoid used is GRS_1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    Attribute Table
    Table containing attribute information associated with the dataset (Source: Producer defined)
    Elevation (NAVD88)
    Elevation relative to the North American vertical datum of 1988 (NAVD88) (Source: Producer Defined)
    Range of values
    Minimum:-13.390
    Maximum:7.574
    Units:meters

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Andrew W. Stevens
    • Joshua B. Logan
    • Alexander G. Snyder
    • Daniel J. Hoover
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Andrew W. Stevens
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Oceanographer
    2885 Mission St.
    Santa Cruz, CA
    USA

    831-460-7424 (voice)
    astevens@usgs.gov

Why was the data set created?

Data were obtained to document changes in shoreline position and coastal morphology as they relate to episodic (storms), seasonal, interannual, and longer (for example, El Niño) processes. These data are intended for science researchers, students, policy makers, and the general public. These data can be used with geographic information systems or other software to identify topographic and shallow-water bathymetric features.

How was the data set created?

  1. From what previous works were the data drawn?
    bathymetry data (source 1 of 3)
    Stevens, Andrew W., and Snyder, Alexander G., 2017, Nearshore bathymetry data from northern Monterey Bay, California, March 2015: U.S. Geological Survey, Pacific Coastal and Marine Science Center, online.

    Online Links:

    Type_of_Source_Media: digital dataset
    Source_Contribution:
    Bathymetry data were combined with topography data, and then interpolated into a gridded surface
    topography data (source 2 of 3)
    Stevens, Andrew W., Logan, Joshua B., Hoover, Daniel J., and Snyder, Alexander G., 2017, Topography data from northern Monterey Bay, California, March 2015: U.S. Geological Survey, Pacific Coastal and Marine Science Center, online.

    Online Links:

    Type_of_Source_Media: digital dataset
    Source_Contribution:
    Topography data were combined with bathymetry data, and then interpolated into a gridded surface
    terrestrial lidar data (source 3 of 3)
    Logan, Joshua B., and Snyder, Alexander G., 2017, Terrestrial lidar data from northern Monterey Bay, California, March 2015: U.S. Geological Survey, Pacific Coastal and Marine Science Center, online.

    Online Links:

    Type_of_Source_Media: digital dataset
    Source_Contribution:
    Topography data were combined with bathymetry data, and then interpolated into a gridded surface
  2. How were the data generated, processed, and modified?
    Date: 13-Oct-2017 (process 1 of 1)
    Quality control was applied to raw topography, terrestrial lidar, and bathymetry data. Comparisons were performed to ensure internal consistency between the survey platforms. DEMs were produced by linear interpolation of all available elevation point data with the computer program MATLAB. Data were exported in ESRI ARC ascii grid format for distribution. Data sources used in this process:
    • bathymetry data, topography data, terrestrial lidar data
  3. What similar or related data should the user be aware of?
    International Hydrographic Organization (IHO), 2008, IHO standards for hydrographic surveys (5th ed.): International Hydrographic Bureau Special Publication 44, 28p., Monaco.

    Online Links:


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

  1. How well have the observations been checked?
    Repeatability tests were conducted across different survey platforms, but no comparisons to "true" values were conducted.
  2. How accurate are the geographic locations?
    Digital elevation models (DEMs) are created by interpolating between elevation measurements as much as 500 meters apart, for this reason we cannot evaluate the accuracy of each point in a DEM, only the original data from which it is generated. The horizontal accuracy of the individual points was assessed based on the combined uncertainty of GNSS data points and terrestrial lidar data. Manufacturer-reported accuracy for the differentially corrected horizontal positions for the GNSS receivers used to collect the topographic and bathymetric measurements is 0.8 cm + 0.5 ppm. Baselines from the GNSS base station varied between 1.5 km and 29 km with a mean of 13 km, suggesting the average horizontal accuracy of survey platform positions to be about 1.5 cm. The average uncertainty in the horiontal coordinates of the terrestrial lidar data is esimated to be 7 cm.
  3. How accurate are the heights or depths?
    Digital elevation models (DEMs) are created by interpolating between elevation measurements as much as 500 meters apart, for this reason we cannot evaluate the accuracy of each point in a DEM, only the original data from which it is generated. An average estimated vertical accuracy of 3 cm for the topographic GNSS backpack- and ATV-survey platforms was estimated by using the manufacturer reported vertical accuracy of 1.5 cm + 1 ppm for differentially corrected kinematic data. The vertical accuracy of the terrestrial lidar data was tested by comparing the final elevation values to concurrently collected topographic GNSS data. The RMS errors calculated for the vertical differences between these data and the point cloud data were typically found to be less than or equal to about 7 cm. Uncertainty in the bathymetry data is related the precision of the GNSS positioning and single-beam echosounders as well as unmeasured variability in the speed of sound used to compute depths from bathymetric soundings. Based on analysis of available speed of sound measurements, we estimate uncertainties in the final depth soundings to be no greater than 1 percent of the water depth. The total vertical uncertainty of the bathymetry data is calculated using the constant- and depth-dependent factors summed in quadrature (International Hydrographic Organization, 2008). The average vertical uncertainty in bathymetry data is estimated to be 9 cm.
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    All data falls within expected ranges.

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:
USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey as the originator(s) of the dataset and in products derived from these data. This information is not intended for navigational purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - Science Base
    U.S. Geological Survey
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    USA

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? DEM grids are available in Esri ARC/INFO ASCII GRID format (mb15_mar_dem_manresa.asc; mb15_mar_dem_mosslanding.asc; mb15_mar_dem_santacruz.asc; mb15_mar_dem_soquelcove.asc), along with low-resolution browse graphics showing the DEMs color-coded by elevation (mb15_mar_dems_overall.png; mb15_mar_dems_inset.png) and associated FGDC-compliant metadata.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display 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.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 22-Nov-2017
Metadata author:
Andrew W. Stevens
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Oceanographer
2885 Mission St.
Santa Cruz, CA
USA

831-460-7424 (voice)
astevens@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/monterey_bay/mb15_mar_dems_metadata.faq.html>
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