Digital elevation models (DEMs) of the lower Elwha River, Washington, water year 2013 to 2016

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Frequently anticipated questions:

What does this data set describe?

Title:
Digital elevation models (DEMs) of the lower Elwha River, Washington, water year 2013 to 2016
Abstract:
Digital elevation models (DEMs) of the lower Elwha River, Washington, were created by synthesizing lidar and PlaneCam Structure-from-Motion (SfM) data. Lidar and still digital photographs were collected by airplane during surveys from 2012 to 2016. The digital photographs were used to create a SfM digital surface model. Each DEM represents the ending conditions for that water year (for example, the 2013 DEM represents conditions at approximately September 30, 2013). The final DEMs, presented here, were created from the most recent lidar before September 30 of a given year, supplemented with an error-corrected SfM model from a low-flow summer Elwha PlaneCam flight as close to 30 September as possible. This synthetic data product was created because the aerial lidar data had gaps near the river, which the SfM data were able to close. The georeferenced DEMs were used to assess the river's responses to the removal of the Elwha and the Glines Canyon dams upstream from the study area.
Supplemental_Information:
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?
    Ritchie, Andrew C, 2018, Digital elevation models (DEMs) of the lower Elwha River, Washington, water year 2013 to 2016: data release doi:10.5066/F7PG1QWC, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    This is part of the following larger work.

    Ritchie, Andrew C, Curran, Christopher A, Magirl, Christopher S, Bountry, Jennifer A, Hilldale, Robert C, Randle, Timothy J, and Duda, Jefferey J, 2018, Data in support of 5-year sediment budget and morphodynamic analysis of Elwha River following dam removals: data release doi:10.5066/F7PG1QWC, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -123.614549
    East_Bounding_Coordinate: -123.541697
    North_Bounding_Coordinate: 48.145105
    South_Bounding_Coordinate: 47.959409
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5a035e8be4b0036f58f947c7?name=2016DEM.png&allowOpen=true (PNG)
    Low-resolution sample of 2016 DEM.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2012
    Ending_Date: 2016
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: 32-bit GeoTIFF digital files
  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 20454 x 5171, type Pixel
    2. What coordinate system is used to represent geographic features?
      The map projection used is Transverse Mercator.
      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 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 1983.
      The ellipsoid used is GRS 1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.2572221.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 1.0E-6
      Altitude_Distance_Units: Meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    Elwha_PlaneCamLidarDEMs_2013to2016.zip
    Zip file containing GeoTIFF digital files (Source: Producer defined)
    Value
    Elevation value at specified horizontal coordinates. (Source: Producer defined)
    Range of values
    Minimum:-33.173332214355
    Maximum:366.92999267578
    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 C Ritchie
  2. Who also contributed to the data set?
    Data collection was funded by U.S. Geological Survey, Environmental Protection Agency, National Park Service, and U.S. Bureau of Reclamation
  3. To whom should users address questions about the data?
    Andrew C Ritchie
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission Street
    Santa Cruz, CA
    United States

    831-460-7454 (voice)
    aritchie@usgs.gov

Why was the data set created?

Data were obtained to assess the morphodynamic and sediment budget responses following the removal of two dams in the Elwha River. 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 features.

How was the data set created?

  1. From what previous works were the data drawn?
    East et al. 2015 (source 1 of 1)
    East, Amy E, Pess, George R, Bountry, Jennifer A, Magirl, Christopher S, Ritchie, Andrew C, Logan, Joshua B, Randle, Timothy J, Mastin, Mark C, Minear, Justin T, Duda, Jefferey J, Liermann, Martin C, McHenry, Michael L, Beechie, Timothy J, and Shafroth, Patrick B, 20150101, Large-scale dam removal on the Elwha River, Washington, USA: river channel and floodplain geomorphic change.: Geomorphology, v. 228, pgs. 765-786, Amsterdam, the Netherlands.

    Online Links:

    Type_of_Source_Media: River profile surveys
    Source_Contribution: River profiles used in creation of 2013_PlaneCamLidar_Final.tif
  2. How were the data generated, processed, and modified?
    Date: 2016 (process 1 of 5)
    Image collection: Images collected before Nov 2014 were collected with a single Canon D10 using firmware hacked with CHDK and running an intervalometer script written in Lua. Until Mar 2016 they were flown with a D10 and a Ricoh GR, and after March they were done with two Ricoh GR cameras. Cameras were mounted in a customized wing mount and flown in four flight lines with a Cessna 172 at elevations between 1500 and 2000 feet above ground level. Image locations were established by matching features in some images with ground control points (GCPs). GCP locations were measured using either a RTK base station or a WSRN network fix using a TopCon GRS-1, Trimble R8 or Trimble R10 receiver. Occupation times were generally 180 seconds and estimated accuracy is 5 cm vertical, 2.5 cm horizontal.
    Date: 2017 (process 2 of 5)
    PlaneCam structure-from-motion processing: Images were aligned using PhotoScan software (Agisoft, LLC). PhotoScan aligns images based on tie points shared between multiple images and scales the resultant 3D surface based on perspective differences between individual images. Geographic location and elevation are introduced to the surface model using the GCP locations in the model. The result of this structure-from-motion processing was the PlaneCam digital surface model (DSM).
    Date: 2017 (process 3 of 5)
    DEM creation: Each DEM was created from the most recent lidar before 30 September of the given year, supplemented with an error corrected structure-from-motion DSM from a low flow summer Elwha PlaneCam flight as close to 30 September as possible. One surface (2014) also contains data from a November 7 2014 lidar flight because the previous flight in 2012 did not capture the 2013 overbank flows. Because higher flows were reached in 2013 than in 2014 before 7 November, this flight was still deemed worthwhile - most of the in-channel data and all of the erosion occurring after the summer 2014 planecam flight were specifically maintained as either summer low flow 2014 PlaneCam data or 2012 lidar data for this DEM.
    DEMs were produced with the following process steps:
    1) most recent lidar data used as a base data layer 2) identify points on hard, flat surfaces where both lidar and PlaneCam had good surface reconstruction resolution and no visible X/Y offset, and where change between multiple lidar flights was +/- less than 0.1 meters (lidar uncertainty) 3) develop error map for PlaneCam surface based on those points using empirical bayesian kriging and a cell size of 20 meters with a linear semivariogram composed of local models with less than or equal to 75 points, a local model overlap factor of 2, and 100 simulated semivariograms per model 4) apply error map to PlaneCam surface model and visually inspect to confirm reduced error (typically expressed as a reduction in large-scale warping in areas of low GCP point density - specifically the middle and lower river away from either reservoir or the river mouth where higher control point densities exist. 5) delineate area where erosion/deposition was active since the last lidar (scale of 1:500 +/- 250) and clip PlaneCam model to that area 6) evaluate surface difference areas for replacement with (1) lowest surface or (2) most recent surface 7) clip out areas of most recent surface as a separate polygon 8) merge rasters selecting the lowest surface between lidar and PlaneCam 9) overwrite merged raster with planecam data where higher but more recent surface accurately reflects channel conditions.
    Several artifacts exist from this merging process:
    1) where lidar data captured high water surfaces and subsequent low flow planecam flight didn't capture dewatered channel features or lower water surface, the higher water surface is an artifact. This is most pronounced in the 2014 DEM because the 2014 Nov 7 DEM was used with a WSE corresponding to flows of 3300-3560 cfs. In some areas, overhanging vegetation prevented PlaneCam surface reconstruction from the corresponding planeCam dem. This artifact is also visible in the 2016 DEM, most notably in the Elwha Canyon between the lower Elwha dam site and the Elwha surface water intake
    2) the 2015 DEM used a topobathy lidar flight that extended to only the Highway 101 bridge. Because these data are more accurate than either the PlaneCam DEM or the previous (Feb 22 2015) DEM, they were used. This may result in an exaggerated estimate of sediment evacuation/recovery from 2014-2015 in the lower river because of (A) the previous issue and (B) the extensive subaqueous coverage of the 2015 topobathy data. Note that topobathy data were only used in-channel and the area outside of the active channel was comprised of the Feb-22-2015 lidar because leaf-off conditions were better for resolving bare earth.
    Data sources are as follows:
    2013_PlaneCamLidar_Final.tif -2012 10-17 October USGS lidar -2013 0919 PlaneCam -river profile surveys (East et al., 2015)
    2014_PlaneCamLidar_Final.tif -2012 10-17 October USGS lidar -2014 30 September PlaneCam -2014 07 November USGS lidar
    2015_PlaneCamLidar_Final.tif -2015 22 February USGS lidar -2015 23 September PlaneCam -2015 28-29 September USGS topobathy lidar
    2016_PlaneCamLidar_Final.tif -2016 29 March USGS lidar -2016 30 September PlaneCam
    Date: 17-Jul-2018 (process 4 of 5)
    Corrected name of theme keyword thesaurus from ISO 19115 Topic Categories to Category. Person who carried out this activity:
    Susan A Cochran
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    2885 Mission St.
    Santa Cruz, CA
    United States

    831-460-7545 (voice)
    scochran@usgs.gov
    Date: 19-Oct-2020 (process 5 of 5)
    Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@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?
    Data set is considered complete with the following notes -- where lidar data captured the high water surfaces and subsequent low flow planecam flight didn't capture dewatered channel features or lower water surface, the higher water surface is an artifact. This is most pronounced in the 2014 DEM because the 2014 Nov 7 DEM was used with a WSE corresponding to flows of 3300-3560 cfs. Vegetation may have created artifacts from the photographic data. This artifact is also visible in the 2016 DEM, most notably in the Elwha Canyon between the lower Elwha dam site and the Elwha surface water intake. The 2015 DEM used a topobathy lidar flight that extended to only the Highway 101 bridge. Because these data are more accurate than either the PlaneCam DEM or the previous (Feb 22 2015) DEM, they were used. This may result in an exaggerated estimate of sediment evacuation/recovery from 2014-2015 in the lower river because of (A) the previous issue and (B) the extensive subaqueous coverage of the 2015 topobathy data. Note that topobathy data were only used in-channel and the area outside of the active channel was comprised of the Feb-22-2015 lidar because leaf-off conditions were better for resolving bare earth.
  2. How accurate are the geographic locations?
    Horizontal positional accuracy is within 0.025 meters.
  3. How accurate are the heights or depths?
    Vertical positional accuracy is within 0.05 meters.
  4. Where are the gaps in the data? What is missing?
    Data set 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: 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 (USGS), Environmental Protection Agency, National Park Service, and the U.S. Bureau of Reclamation as the originators of the dataset and in products derived from these data.
  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? These data are available in GeoTIFF format, one GeoTIFF per water year, contained in a single zip file (Elwha_PlaneCamLidar_2013to2016.zip), which also includes 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?
  5. What hardware or software do I need in order to use the data set?
    This zip file contains GeoTIFF files and can be uncompressed with any unzipping software, such as WinZip. The GeoTIFF files can be viewed in geographic information system (GIS) software as a geographically located digital elevation model.

Who wrote the metadata?

Dates:
Last modified: 19-Oct-2020
Metadata author:
Andrew C Ritchie
U.S. Geological Survey, Pacific Coastal and Marine Science Center
2885 Mission Street
Santa Cruz, CA
United States

831-460-7454 (voice)
aritchie@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_F7PG1QWC/Elwha_PlaneCamLidarDEMs.faq.html>
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