Orthomosaic images of the middle and lower Elwha River, Washington, 2012 to 2017

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Frequently anticipated questions:

What does this data set describe?

Orthomosaic images of the middle and lower Elwha River, Washington, 2012 to 2017
This dataset presents 28 georeferenced orthomosaic images of the middle and lower reaches of the Elwha River. Each mosaic image was created by stitching together thousands of individual photographs that were matched based on numerous unique tie points shared by the photographs. The individual photographs were taken by a plane-mounted camera during multiple flights over the study area spanning 2012 to 2017. Because each mosaic is orthogonal to the earth's surface and is georeferenced to real-world coordinates, changes to the river channel and surrounding morphology can be seen and measured, including channel width, river braiding, bar formation, and other metrics to assess responses of the river to the removal of two large dams upstream from the study area.
  1. How might this data set be cited?
    Ritchie, Andrew C, 2018, Orthomosaic images of the middle and lower Elwha River, Washington, 2012 to 2017: 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: -123.568000
    East_Bounding_Coordinate: -123.549187
    North_Bounding_Coordinate: 48.1516437
    South_Bounding_Coordinate: 48.0940000
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/5a035ecee4b0036f58f947cc?name=ElwhaOrthomosaic.png&allowOpen=true (PNG)
    Low-resolution sample orthomosaic.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2012
    Ending_Date: 2016
    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?
      Indirect_Spatial_Reference: Data were collected over the Elwha River, Washington.
      This is a Raster data set.
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 1.5E-6. Longitudes are given to the nearest 1.5E-6. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1983 National Spatial Reference System 2007.
      The ellipsoid used is Geodetic Reference System 80 (GRS80).
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.26.
  7. How does the data set describe geographic features?
    Three-band GeoTIFF image.
    Pixel based raster matrix with 3 layers of information for each pixel. The filename for each image is formatted as "date_Elwha_reach.tif", where date is the date the images were collected (in YYYYMMDD format), and reach is either LR or MR ("lower reach" or "middle reach," respectively). (Source: Other)
    Red wavelength band. (Source: Agisoft Photoscan)
    Range of values
    Green wavelength band. (Source: Agisoft Photoscan)
    Range of values
    Blue wavelength band. (Source: Agisoft Photoscan.)
    Range of values

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 and National Park Service
  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)

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 visible features.
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

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: 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 1,500 and 2,000 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)
    Orthomosaic creation: 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. PhotoScan exports an orthomosaic image by converting the 3D surface model into an orthogonal 2D surface. Pixel values for the orthomosaics in this dataset were blended using a weighted average of all pixel values from all the images used.
    Date: 2017 (process 3 of 5)
    Each orthomosaic was tiled with tile dimensions 256 by 256 pixels and compressed at 90% using JPEG compression and YCbCr color space.
    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)
    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)
  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?
    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
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) 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)
  2. What's the catalog number I need to order this data set? data are downloadable in .zip format (Elwha_Orthos_2012to2017.zip) along with CMGDS 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?

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)
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_Orthos_2012to2017.faq.html>
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