Acoustic-backscatter data collected in 2016 offshore the Elwha River mouth, Washington, during USGS Field Activity 2016-605-FA
These metadata describe acoustic-backscatter data collected during a 2016 SWATHPlus-M survey offshore the Elwha River mouth, Strait of Juan de Fuca, Washington. Data were collected and processed by the U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center (PCMSC) with fieldwork activity number 2016-605-FA. The acoustic-backscatter data are provided as a GeoTIFF image in UTM, zone 10, NAD83 coordinates.
Additional information about the field activity from which these data were derived is available online at:
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.
Dartnell, Peter, and Warrick, Jonathan A., 20201104, Acoustic-backscatter data collected in 2016 offshore the Elwha River mouth, Washington, during USGS Field Activity 2016-605-FA: data release DOI:10.5066/P9YVVAMT, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.
Dartnell, Peter, and Warrick, Jonathan A., 2020, Bathymetry and acoustic-backscatter data collected in 2016 offshore the Elwha River mouth, Washington, during USGS Field Activity 2016-605-FA: data release DOI:10.5066/P9YVVAMT, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.
Planar coordinates are encoded using row and column
Abscissae (x-coordinates) are specified to the nearest 2.0
Ordinates (y-coordinates) are specified to the nearest 2.0
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1983 (2011).
The ellipsoid used is Geodetic Reference System 96.
The semi-major axis of the ellipsoid used is 6378137.
The flattening of the ellipsoid used is 1/298.257.
The raw 16-bit backscatter recorded simultaneously with the bathymetry by the SWATHplus was gain-normalized by the program SonarWiz. The program normalizes for time-varying signal loss and beam directivity differences. The resulting normalized amplitude values are re-scaled to 16-bit, exported as an Imagine image. Normalized acoustic backscatter shows the relative strength of the acoustic signal returned from the seafloor.
(Source: Producer defined)
The complete 2016 2-m resolution image "2016_ElwhaDelta_2m_backscatter_UTM10_NAD83.tif" was originally archived as a TIFF image with the following attributes.
Cell size = 1.0
Number of rows = 2713
Number of columns = 4974
Data type = floating point
Xmin = 454923
Xmax = 464873
Ymin = 5329866
Ymax = 5335293
Minimum value = 63.98
Maximum value = 146.00
Mean = 99.81
Standard deviation = 9.88
Coordinate system description
Sonar-based surveys of the seafloor around the Elwha River mouth, Strait of Juan de Fuca, Washington were conducted to map changes that have occurred following sediment input from dam removals from the Department of the Interior's Elwha River Restoration Project. This project resulted in the removal of two large dams on the Elwha River during 2011-2014, which released millions of tonnes of sediment to the river and coast. Similar sonar-based surveys were conducted before the dam removals in 2008 and 2010 by the USGS, and these pre-removal surveys may be used for comparisons with the data provided herein. Collaborative partners in this work include the Lower Elwha Klallam Tribe.
The Swath survey was conducted with a SWATHplus-M 234-kHz interferometric side-scan sonar system pole-mounted on the U.S. Geological Survey (USGS) R/V Parke Snavely. 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 Applanix POS-MV Smoothed Best Estimate of Trajectory (SBET) data were merged with each original survey line file using Bathyswath processing software to create new post-processed survey line files. The post-processed line files were imported into SonarWiz software (version 6) for backscatter processing. A processed backscatter grid was exported as an Imagine image in UTM zone 10 WGS84 coordinates. The image was imported into ArcGIS and projected to UTM zone 10, NAD83 coordinates using the ArcTools project raster function. The backscatter image was then exported as a GeoTIFF image in UTM zone 10, NAD83 coordinates.
Date: 17-Mar-2021 (process 2 of 3)
Corrected working URL links to cmgds data repository to the actual published links
Person who carried out this activity:
U.S. Geological Survey
Attn: Susan A. Cochran
2885 Mission Street
Santa Cruz, CA
Date: 13-Oct-2021 (process 3 of 3)
Performed minor edits to the metadata to correct typos. No data were changed
Person who carried out this activity:
How accurate are the geographic locations?
Uncertainty in the horizontal position of each sounding is a function of the total uncertainty propagated through each of the following component instruments: 1) vessel GPS, 2) intertial motion unit (IMU), 3) water sound velocity model, and 4) beam spreading in the water column. Assuming no systematic errors in the measurement instruments themselves, beam spreading is the dominate source of positional uncertainty. The 1-degree sonar beam of the SWATHplus-M results in horizontal uncertainty ranging from 0.10 m at 10 m slant range, to about 0.45 m at 50 m slant range. Accuracies of final products may be lower due to data processing that includes sounding cleaning, gridding, and datum transformations.
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.
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.
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.