Bathymetry data for Lake Sammamish, Washington collected during USGS field activity 2021-656-FA

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Frequently anticipated questions:

What does this data set describe?

Title:
Bathymetry data for Lake Sammamish, Washington collected during USGS field activity 2021-656-FA
Abstract:
Here November 2021 2-m resolution bathymetry data of Lake Sammamish, Washington are provided for the entire lake. Data were collected and processed by the U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC) with fieldwork activity number 2021-656-FA. Data are provided as a GeoTIFF image.
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=2021-656-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 data set 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?
    Dartnell, Peter, Brothers, Daniel S., Sherrod, Brian, Hatcher, Gerald A., Powers, Daniel C., Hill, Jenna C., Currie, Jackson E., and Ferro, Peter Dal, 20250917, Bathymetry data for Lake Sammamish, Washington collected during USGS field activity 2021-656-FA: data release DOI:10.5066/P1YKDHGC, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Dartnell, Peter, Brothers, Daniel S., Sherrod, Brian, Hatcher, Gerald A., Powers, Daniel C., Hill, Jenna C., Currie, Jackson E., and Ferro, Peter Dal, 2025, Bathymetry and acoustic-backscatter data for Lake Sammamish, Washington collected during USGS field activity 2021-656-FA: data release DOI:10.5066/P1YKDHGC, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Dartnell, P., Brothers, D.S., Sherrod, B., Hatcher, G.A., Powers, D.C., Hill, J.C., Currie, J.E., Dal Ferro, P., 2025, Bathymetry and acoustic-backscatter data for Sammamish Lake, Washington collected during USGS field activity 2021-656-FA: U.S. Geological Survey data release, https://doi.org/10.5066/P1YKDHGC.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -122.200
    East_Bounding_Coordinate: -121.966
    North_Bounding_Coordinate: 47.652
    South_Bounding_Coordinate: 47.557
  3. What does it look like?
    LakeSammamish_USGS_2021_2m_bathymetry_UTM10_NAD83_NAVD88_QV.jpg (JPEG)
    Preview image of USGS 2021 Lake Sammamish bathymetry
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 08-Nov-2021
    Ending_Date: 12-Nov-2021
    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 5380 x 8710 x 1, 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: -123.00000
      Latitude_of_Projection_Origin: 0.00000
      False_Easting: 500000.0
      False_Northing: 0.00
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 1.0
      Ordinates (y-coordinates) are specified to the nearest 1.0
      Planar coordinates are specified in Meters
      The horizontal datum used is North American Datum of 1983, 2011 realization (NAD83(2011)).
      The ellipsoid used is GRS80.
      The semi-major axis of the ellipsoid used is 6378137.00.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North America Vertical Datum 1988
      Altitude_Resolution: 0.1
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    value
    elevation in meters relative to NAVD-88 (Source: Producer defined)
    Entity_and_Attribute_Overview:
    The complete 2-m resolution grid "LakeSammamish_USGS_2021_2m_bathymetry_UTM10_NAD83_NAVD88.tif" was originally archived as a TIFF image with the following attributes. 
    Cell size = 2.0
Number of rows = 5380
Number of columns = 8710

Data type = floating point

Boundary
Xmin = 560211
Xmax = 577634
Ymin = 5267349
Ymax = 5278111

Statistics
Minimum value = -25.03
Maximum value = 9.86
Mean = -10.76
Standard deviation = 5.96

Coordinate system description
Projection:  UTM
Zone:  10
Datum:  NAD83(2011)
Vertical Reference: NAVD88
Units:  meter
    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)
    • Peter Dartnell
    • Daniel S. Brothers
    • Brian Sherrod
    • Gerald A. Hatcher
    • Daniel C. Powers
    • Jenna C. Hill
    • Jackson E. Currie
    • Peter Dal Ferro
  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?

The Pacific Northwest is home to numerous faults that cut through the surrounding crust including the Seattle fault. Over time, frictional stresses accumulate along these faults, building slowly until they exceed the fault's strength, resulting in an earthquake. Evidence of these earthquakes may be found in Pacific Northwest lakes. Past underwater landslides caused by the earthquakes should be well preserved in these relatively undisturbed environments. The lake floor of Lake Sammamish in the Pacific Northwest was mapped to find such evidence of past earthquakes. 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 bathymetric features. These data are not intended to be used for navigation.

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: 2022 (process 1 of 1)
    The data were collected with a SWATHplus-M 234-kHz interferometric side-scan sonar system pole-mounted on the U.S. Geological Survey (USGS) R/V San Lorenzo. During the mapping mission, an Applanix POS-MV (Position and Orientation System for Marine Vessels) was used to position the vessel during data collection, and it also accounted for vessel motion such as heave, pitch, and roll. The POS-MV also recorded position and vessel motion parameters for later post-processing. Sound-velocity profiles were collected throughout the survey days with a Castaway sound velocimeter. Post-processed POS-MV Smoothed Best Estimate of Trajectory (SBET) files were merged with the survey line files using BathySwath software and then the line files were imported into SonarWiz software. Soundings were cleaned for obvious errors and gridded into a 2-m base surface. The base surface was exported as an Erdas Imagine file in UTM-10, WGS-84 coordinates vertically referenced to the WGS84 ellipsoid. The data were transformed from WGS-84 to NAD-83 horizontal coordinates using ArcGIS Pro ArcTool raster projection command WGS_1984_(ITRF08)_To_NAD_1983_2011. NOAA's on-line VDATUM transformation tool states there is a +23.688m difference between WGS-84 and NAVD-88 elevations (vertical uncertainty of 0.06m) at a point in the center of the lake. A value of 23.688m was added to the original bathymetry grid to transform from WGS-84 elevations to NAVD-88 elevations. The NAVD-88 bathymetry grid was then exported as a GeoTIFF file in UTM zone 10, NAD-83(2011) coordinates, relative to NAVD88.
  3. What similar or related data should the user be aware of?
    Dartnell, Peter, Brothers, Daniel S., Sherrod, Brian, Hatcher, Gerald A., Powers, Daniel C., and Hill, Jenna C., 2025, Bathymetric and acoustic-backscatter mapping of Lake Sammamish, Washington, during USGS field activity 2021-656-FA.

    Online Links:

    Other_Citation_Details:
    Dartnell, P., Brothers, D.S., Sherrod, B., Hatcher, G.A., Powers, D.C., and Hill, J.C., 2025, Bathymetric and acoustic-backscatter mapping of Lake Sammamish, Washington, during USGS field activity 2021-656-FA: U.S. Geological Survey Data Report 1207, https://doi.org/10.3133/dr1207

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

  1. How well have the observations been checked?
    The SWATHPlus sonar system (234 kHz) depth standard deviation varies with horizontal range and water depth. The system has an estimated depth standard deviation ranging from about 0.1 m to 0.7 m over a horizontal range of 0 to greater than 100 m (https://doi.org/10.3390/rs14092011). Accuracies of final products may be lower due to 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. Refer to data report, Dartnell and others, 2024, for other accuracy assessments.
  2. How accurate are the geographic locations?
    The Applanix POS-MV post-processed horizontal positional accuracy is about 0.1 m with roll and pitch accuracies of about 0.02 degrees (https://www.applanix.com/downloads/products/specs/posmv/POS-MV-WaveMaster-II.pdf). Accuracies of final products may be lower due to 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?
    The Applanix POS-MV post-processed vertical positional accuracy is about 0.2 m (https://www.applanix.com/downloads/products/specs/posmv/POS-MV-WaveMaster-II.pdf). Accuracies of final products may be lower due to 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?
    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?
    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 No access constraints
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 originators 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 - CMGDS
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
    pcmsc_data@usgs.gov
  2. What's the catalog number I need to order this data set? These data are available in GeoTIFF format, including a tif world file (.tfw), accompanied by CSDGM 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?
    • Availability in digital form:
      Data format: Downloadable zip file contains the TIFF (.tif) version of the bathymetry data and a projection file (.tfw). in format GeoTIFF (version ArcMap (version 10.3.1)) Size: 14.4
      Network links: https://doi.org/10.5066/P1YKDHGC
    • Cost to order the data: None.

  5. What hardware or software do I need in order to use the data set?
    The downloadable data file has been compressed with the "zip" command and can be unzipped with Winzip (or other tool) on Windows systems. To utilize these data, the user must have software capable of uncompressing the WinZip file and importing and viewing a GeoTIFF file.

Who wrote the metadata?

Dates:
Last modified: 17-Sep-2025
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/CMGDS_DR_tool/DR_P1YKDHGC/LakeSammamish_USGS_2021_2m_bathymetry_UTM10_NAD83_NAVD88_metadata.faq.html>
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