4-m Image of the Northern Half of the Backscatter Intensity Mosaic of the Sea Floor off Northeastern Cape Cod from USGS Cruise 98015 (CAPENORTHMOS_GEO4M_WGS84.TIF, Geographic, WGS84)

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Frequently anticipated questions:


What does this data set describe?

Title:
4-m Image of the Northern Half of the Backscatter Intensity Mosaic of the Sea Floor off Northeastern Cape Cod from USGS Cruise 98015 (CAPENORTHMOS_GEO4M_WGS84.TIF, Geographic, WGS84)
Abstract:
This data set includes backscatter intensity of the sea floor offshore of northern Cape Cod, Massachusetts. The data were collected with a multibeam sea floor mapping system during USGS survey 98015, conducted November 9 - 25, 1998. The surveys were conducted using a Simrad EM 1000 multibeam echo sounder mounted aboard the Canadian Coast Guard vessel Frederick G. Creed. This multibeam system utilizes 60 electronically aimed receive beams spaced at intervals of 2.5 degrees that insonify a strip of sea floor up to 7.5 times the water depth (swath width of 100 to 200 m within the survey area). The horizontal resolution of the beam on the sea floor is approximately 10% of the water depth. Vertical resolution is approximately 1 percent of the water depth. With backscatter intensity, the intensity of the acoustic return from the sea floor from the multibeam system, is a function of the properties of the surficial sediments and of the bottom roughness. Generally, a strong return (light gray tones) is associated with rock or coarse-grained sediment, and a weak return (dark gray tones) with fine-grained sediments. However, the micro-topography, such as ripples, burrows, and benthic populations also affect the reflectivity of the sea floor. Direct observations, using bottom photography or video, and surface samples, are needed to verify interpretations of the backscatter intensity data. The backscatter data have a weak striping that runs parallel to the ship's track. Some of the striping is the result of poor data return at nadir that appears as evenly-spaced thin speckled lines. Some striping is also due to critical angle effects, where the intensity of return varies as a function of the angle of incidence of the incoming sound on the seafloor (Hughes-Clark and others, 1997).
  1. How might this data set be cited?
    U.S. Geological Survey, 2006, 4-m Image of the Northern Half of the Backscatter Intensity Mosaic of the Sea Floor off Northeastern Cape Cod from USGS Cruise 98015 (CAPENORTHMOS_GEO4M_WGS84.TIF, Geographic, WGS84): Open-File Report 2005-1048, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.

    Online Links:

    This is part of the following larger work.

    Poppe, L.J., Paskevich, V.F., Butman, B., Valentine, P.C., Danforth, W.W., Foster, D.S., and Blackwood, D.S., 2005, Geological Interpretation of Bathymetric and Backscatter Imagery of the Sea Floor off Eastern Cape Cod, Massachusetts: Open-File Report 2005-1048, U.S. Geological Survey, Reston, VA.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.307833
    East_Bounding_Coordinate: -69.828333
    North_Bounding_Coordinate: 42.116667
    South_Bounding_Coordinate: 41.966667
  3. What does it look like?
    http://pubs.usgs.gov/of/2005/1048/data/backscatter/mosaic/geo/capenorthmos_geo4m_wgs84-thumb.gif (GIF)
    Thumbnail image showing the extent and coverage of the data layer.
    http://pubs.usgs.gov/of/2005/1048/data/backscatter/mosaic/geo/capenorthmos_geo4m_wgs84.gif (GIF)
    Image map showing the extent and coverage of the data layer.
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 09-Nov-1998
    Ending_Date: 25-Nov-1998
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: remote-sensing image
  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 4191 x 9986 x 1, type Pixel
    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 0.000036. Longitudes are given to the nearest 0.000048. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is World Geodetic System 84.
      The ellipsoid used is World Geodetic System 84.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257.
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview: There are no attributes associated with the GEOTIFF image.
    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)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Lawrence J. Poppe
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    (508) 548-8700 x2314 (voice)
    (508) 457-2310 (FAX)
    lpoppe@usgs.gov

Why was the data set created?

To release a digital map derived from multibeam observations that shows sea floor backscatter intensity (a measure of sea floor texture and roughness) at a spatial resolution of 4 meters per pixel.

How was the data set created?

  1. From what previous works were the data drawn?
    98015_multibeam_data (source 1 of 1)
    USGS, unpublished material, Raw multibeam backscatter data.

    Other_Citation_Details:
    This file had a source contribution, but no source citation information. This information was populated based on information in the source contribution.
    Type_of_Source_Media: DVD-ROM
    Source_Contribution:
    The original multibeam backscatter data acquired with a Simrad EM 1000 echosounder during USGS cruise 98015 aboard the Canadian Coast Guard vessel Frederick G. Creed
  2. How were the data generated, processed, and modified?
    Date: Unknown (process 1 of 5)
    Initial Data and acquisition processing at sea: After the echo sounder data were logged onto the hard disk of the Sun workstation, a suite of processing software developed by the Ocean Mapping Group (www.omg.unb.ca/~jhc/SwathEd.html) was used to correct for artifacts and errors that may have been introduced during data collection. This software also enhanced the corrected data by resolving beam pattern and aspect ratio distortions and by imposing a linear contrast stretch before it generated bathymetric and sidescan sonar image mosaics in a Mercator projection. All data processing described here is initiated using Silicon Graphics workstations as soon as each acquisition file is closed by the Simrad Mermaid workstation (usually at the end of each survey line). Additional processing was done in the lab to correct for fluctuations in sea level during the survey and for artifacts in the data files that were not corrected in the field (see below). The processing and editing steps on board the ship were: (A.) Demultiplex, or unravel, the acquired Simrad data files using RT to generate separate files containing navigation, depth soundings, sidescan sonar backscatter values, and sound velocity information. (B.) Automatically reject bad data (autoRejectSoundings). For the multibeam soundings, reject data outside expected depth ranges (operator's decision based on nautical chart data); for navigation data, reject fixes with poor GPS statistics. (C.) Edit the navigation data on-screen using jview to remove undesirable points, including turns at the ends of survey lines. (D.) Edit the multibeam soundings on-screen using swathed to remove individual anomalous soundings. (E). Merge tidal information and the corrected navigation back (mergetide and mergenav) into the data files. Tidal information was obtained from predicted tides using the Xtide program http://www.flaterco.com/xtide/xtide.html), which generated predicted tides based on the harmonic coefficients for Chatham provided by the Xtide program. (F.) Map the bathymetric soundings from each processed data file onto a Mercator grid using weigh_grid with node spacings and scale selected by the operator. The data files capenorth.asc and capenorth.xyz were produced from the gridded data. The data file capenorth.txt is a comma-delimited version of capenorth.xyz. (G.) Map the extracted sidescan sonar backscatter values onto a digital mosaic using mos2 in the Mercator projection at a scale selected by the user. Person who carried out this activity:
    Bill Danforth
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    (508) 548-8700 x2274 (voice)
    (508) 457-2310 (FAX)
    bdanforth@usgs.gov
    Data sources used in this process:
    • 98015_multibeam_data
    Data sources produced in this process:
    • capenorth.asc
    • capenoth.xyz
    • capenorth.txt
    • capenorthmos_mer4m.tif
    Date: Unknown (process 2 of 5)
    Map the extracted sidescan sonar backscatter values onto a digital mosaic using the SwathEd utility mos2 in the Mercator projection, having a central longitude of -70.3166667 degrees West, a latitude of true scale of 41.65 degrees north and the horizontal datum is WGS84. Person who carried out this activity:
    Bill Danforth
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    (508) 548-8700 x2274 (voice)
    (508) 457-2310 (FAX)
    bdanforth@usgs.gov
    Data sources used in this process:
    • capenorth.asc
    • capenorth.xyz
    • capenorth.txt
    Data sources produced in this process:
    • capenorthmos_mer4m.tif
    Date: 2004 (process 3 of 5)
    The imagery in Mercator projection was converted to geographic. Person who carried out this activity:
    Valerie Paskevich
    U.S. Geological Survey
    Information Technology Specialist / GIS Coordinator
    384 Woods Hole Road
    Woods Hole, MA
    USA

    (508) 548-8700 x2281 (voice)
    (508) 457-2310 (FAX)
    vpaskevich@usgs.gov
    Data sources used in this process:
    • capenorthmos_mer4m.tif
    Data sources produced in this process:
    • capenorthmos_mer4m_wgs84.tif
    Date: 09-Nov-2015 (process 4 of 5)
    Edits to the metadata were made to fix any errors that MP v 2.9.30 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Most issues were with blank elements that could actually be removed. This file had a source contribution, but no source citation information. This information was populated based on information in the source contribution. Also, both geographic and planar coordinate systems, a common problem when using ArcCatalog. Other minor edits were probably performed (title, publisher, publication place, etc.). The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
    Date: 20-Jul-2018 (process 5 of 5)
    USGS Thesaurus keywords added to the keyword section. 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?
  2. How accurate are the geographic locations?
    These data were navigated with a Differential Global Positioning System (DGPS); they are accurate to +/- 3 meters, horizontally.
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    This image is complete; all available data were used to create the backscatter mosaic; no further processing and(or) modifications will be made.
  5. How consistent are the relationships among the observations, including topology?
    Information unavailable from original metadata.

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:
Public domain data are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.
  1. Who distributes the data set? (Distributor 1 of 1)
    Lawrence J. Poppe
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA
    USA

    (508) 548-8700 x2314 (voice)
    (508) 457-2310 (FAX)
    lpoppe@usgs.gov
  2. What's the catalog number I need to order this data set? Downloadable Data: capenorthmos_geo4m_wgs84.tif
  3. What legal disclaimers am I supposed to read?
    Although all data have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  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 image is available as a GeoTIFF image with an accompanying world file. To utilize this data, the user must have an image viewer, image processing or GIS software package capable of importing a GeoTIFF image.

Who wrote the metadata?

Dates:
Last modified: 20-Jul-2018
Metadata author:
William Danforth
U.S. Geological Survey
Geologist
384 Woods Hole Road
Woods Hole, MA
USA

(508) 548-8700 x2274 (voice)
(508) 457-2310 (FAX)
bdanforth@usgs.gov
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/eastcoast/gome/capecod/capenorthmos_geo4m_wgs84.tif.faq.html>
Generated by mp version 2.9.49 on Mon Sep 10 17:45:03 2018