Digital Elevation Model of Oxbow Reservoir, Placer County, California, October 2022

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Frequently anticipated questions:

What does this data set describe?

Title:
Digital Elevation Model of Oxbow Reservoir, Placer County, California, October 2022
Abstract:
This portion of the data release presents a digital elevation model (DEM) of portions of Oxbow Reservoir in Placer County, California. The DEM was created using topographic survey data collected on 26 October 2022, when the reservoir was partially de-watered to allow repairs to the dam infrastructure following the Mosquito Fire. Although the gates of the dam were open during this time, significant portions of the reservoir site remained inaccessible to surveyors due to the continued flow of the Middle Fork American River. Consequently, this DEM covers approximately 50 percent of the total surface area of the reservoir at full pool. The raw topographic data for the DEM were collected using two RTK GNSS backpack rovers which were referenced to a temporary GNSS base station occupying a fixed control point ("CP512") located less than 1 kilometer from the survey area. Precise coordinates for the GNSS base station were derived using the National Geodetic Survey (NGS) Online Positioning User Service (OPUS). The GNSS data were used to create a triangulated irregular network (TIN), which was converted to raster DEM. The resulting DEM has a horizontal resolution of 1 meter and is formatted as a GeoTIFF.
Supplemental_Information:
Additional information about the field activity from which these data were derived is available online at:
https://cmgds.marine.usgs.gov/fan_info.php?fan=2022-666-FA
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Although this Federal Geographic Data Committee-compliant metadata file is intended to document the dataset in nonproprietary form, as well as in Esri format, this metadata file may include some Esri-specific terminology.
  1. How might this data set be cited?
    Logan, Joshua B., and East, Amy E., 20231030, Digital Elevation Model of Oxbow Reservoir, Placer County, California, October 2022: data release DOI:10.5066/P9B39W4J, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Logan, Joshua B., and East, Amy E., 2023, Topographic survey data and digital elevation model of Oxbow Reservoir, Placer County, California, October 2022: data release DOI:10.5066/P9B39W4J, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Logan, J.B. and East, A.E., 2023, Topographic survey data and digital elevation model of Oxbow Reservoir, Placer County, California, October 2022: U.S. Geological Survey data release, https://doi.org/10.5066/P9B39W4J.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -120.74457
    East_Bounding_Coordinate: -120.73185
    North_Bounding_Coordinate: 39.00609
    South_Bounding_Coordinate: 39.00018
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/65135f92d34eeedefc13c19f?name=OxbowReservoirDEM_browse.jpg&allowOpen=true (JPEG)
    Color-shaded relief image of the Oxbow Reservoir DEM.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 26-Oct-2022
    Currentness_Reference:
    ground condition at time data were collected
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: GeoTIFF
  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. It contains the following raster data types:
      • Dimensions, type Grid Cell
    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 1.000
      Ordinates (y-coordinates) are specified to the nearest 1.000
      Planar coordinates are specified in meters
      The horizontal datum used is NAD83 (National Spatial Reference System 2011) (EPSG:1116).
      The ellipsoid used is GRS 1980 (EPSG:7019).
      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 (EPSG:5703), derived using GEOID18
      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?
    GeoTIFF
    GeoTIFF containing elevation values. (Source: Producer defined)
    Entity_and_Attribute_Overview:
    GeoTIFF raster contains elevations in meters relative to the North American Vertical Datum of 1988 (NAVD88).
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Joshua B. Logan
    • Amy E. East
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

These data are intended to be used as a record of baseline bottom sediment elevation in Oxbow Reservoir immediately after the Mosquito Fire, prior to the first post-fire runoff of the winter of 2022-2023.

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: 26-Oct-2022 (process 1 of 2)
    A topographic survey was conducted using two multi-constellation dual-frequency RTK GNSS rovers (Trimble R10-2) receiving differential corrections from a GNSS base station operating less than 1 kilometer away. The rovers were mounted on GPS backpacks, and were operated in continuous survey mode, collecting data at rate of 1 Hz. The surveyors walked on all exposed reservoir sediment bars which were accessible during the survey. The surveyors attempted to survey along breaks in slope, water surface elevation contours, with additional data in broad planar areas in order to adequately define the topographic surface. Additional survey data were collected along pre-defined "zig-zag" transects which could be re-occupied with a boat during a possible future bathymetric survey with the reservoir at full pool.
    The GNSS base station was placed on an existing control point, "CP512", on the west shoulder of Tahoe National Forest Road 0023-004, approximately 100 meters north of the reservoir below the junction with Forest Road 0023 and Forest Road 0023-02. The reference position provided for CP512 were: CP512-PCWA (SPCS83 California zone 2, ft) Northing: 2129745.418 Easting: 6919711.944 Elevation: 1486.07 (assumed ft., NGVD29)
    During the RTK survey, the GNSS base station was set to collect static observations, and these were submitted to the National Geodetic Survey (NGS) Online Positioning User Service (OPUS-S). The OPUS solution was of high quality, conforming to USGS Level III quality for a single-base OPUS-S survey. The coordinates of the OPUS-S solution are below: CP512-USGS (NAD83(2011) UTM Zone 10, meters) Northing: 4319590.574 Easting: 695699.448 Elevation: 453.791 (NAVD88, meters, derived using GEOID18)
    The newly derived position for CP512 was used to adjust all of the topographic survey data collected during the survey. Person who carried out this activity:
    Joshua Logan
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA

    831-460-7519 (voice)
    jlogan@usgs.gov
    Date: 2023 (process 2 of 2)
    DEM development: 1. Topographic data points were filtered to remove points with poor estimated vertical accuracy. 2. Approximately 3 percent of the remaining points (n=631) were randomly selected and withheld from the data set to serve as a validation set (described in the Vertical Positional Accuracy portion of this document). 3. ArcGIS Pro was used to create a Triangulated Irregular Network (TIN) with the remaining points. 4. Breaklines were added manually along the main river channel portions to reduce interpolation errors in these locations. 5. The TIN was edited to define the interpolation boundary extent (removing long triangles from the exterior). 6. The TIN was exported to a GeoTIFF raster with a pixel resolution of 1 meter. Person who carried out this activity:
    Joshua Logan
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Physical Scientist
    2885 Mission Street
    Santa Cruz, CA
    US

    831-460-7519 (voice)
    831-427-4748 (FAX)
    jlogan@usgs.gov
  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?
    No formal attribute accuracy tests were conducted.
  2. How accurate are the geographic locations?
    No formal horizontal accuracy tests were performed. The topographic survey data used to create the DEM were collected using multi-constellation dual-frequency RTK GNSS rovers receiving differential corrections from a base station operating less than 1 kilometer away. The average estimated horizontal precision of the topographic survey data was 0.028 meters at the 95 percent confidence level. Additional uncertainty related to the reference position of the GNSS base station is estimated to be 0.040 at the 95 percent confidence level, based on the NGS OPUS position solution report which was used to derive the position. Combining the estimated single point precision of the topographic survey data with the estimated uncertainty in the position of the GNSS base station reference point results in a total estimated horizontal accuracy of 0.049 meters at the 95 percent confidence level. Additional sources of error such as antenna height measurement errors, and errors resulting from the GPS antenna not being perfectly level during continuous surveying sessions may be present in the data but the magnitudes of such errors are unknown. It should be noted that the magnitudes of these errors are exceeded by the 1-meter horizontal resolution of the DEM.
  3. How accurate are the heights or depths?
    Vertical accuracy of the DEM was estimated by withholding 631 randomly selected check points from the original topographic survey data set and comparing the elevations of those points with the DEM. The resulting vertical RMSE for these 631 points was 0.101 meters (0.198 meters at the 95 percent confidence level) which represents the relative precision of the DEM. Additional uncertainty related to the reference position of the GNSS base station is estimated to be 0.064 meters (0.125 at the 95 percent confidence level), based on the NGS OPUS position solution report which was used to derive the position. Combining the vertical RMSE of the DEM with the estimated uncertainty in the position of the GNSS base station reference point results in a total estimated vertical accuracy of 0.120 meters (0.234 meters at the 95 percent confidence level). It should be noted that there are likely additional interpolation errors with unknown magnitudes in some portions of the DEM resulting from interpolation across breaks in slope which may have been poorly defined during the topographic survey.
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. During the survey significant portions of the reservoir bottom remained under water and inaccessible to surveyors. Consequently, this DEM covers approximately 50 percent of the total surface area of the reservoir at full pool.
  5. How consistent are the relationships among the observations, including topology?
    No formal logical accuracy tests were conducted.

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 navigation purposes.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    United States

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? The Oxbow Reservoir DEM is available as a GeoTIFF file.
  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?
  5. What hardware or software do I need in order to use the data set?
    These data can be viewed with GIS software or other software capable of displaying geospatial raster data.

Who wrote the metadata?

Dates:
Last modified: 30-Oct-2023
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/ScienceBase/DR_P9B39W4J/OxbowReservoir_2022-10-26_DEM_1m_metadata.faq.html>
Generated by mp version 2.9.51 on Fri Nov 3 14:41:46 2023