USGS logo - www.usgs.gov

CAPENORTHSUN_MER4M.TIF: Image of the 4-m Sun-Illuminated Topography of the Sea Floor off Northeastern Cape Cod (Mercator)

Metadata also available as: OUTLINE | TEXT

Frequently-anticipated questions:

What does this data set describe?

Title:
CAPENORTHSUN_MER4M.TIF: Image of the 4-m Sun-Illuminated Topography of the Sea Floor off Northeastern Cape Cod (Mercator)
Abstract:
This data set includes sun-illuminated bathymetry 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 echosounder 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.

The sun-illuminated topographic (shaded relief) image has a 4-m pixel size and was created by vertically exaggerating the topography two times and then artificially illuminating the relief by a light source positioned 45 degrees above the horizon from an azimuth of 0 degrees. In the resulting image, topographic features are enhanced by strong illumination on the northwestward-facing slopes and by shadows cast on southeastern slopes. The image also accentuates small features (relief of a few meters) that could not be effectively shown as contours alone at this scale. Unnatural-looking features or patterns oriented parallel or perpendicular to survey tracklines are artifacts of data collection and environmental conditions.

Supplemental_Information:
Relief or hill shading is used to visually enhance the terrain features by simulating the appearance of the effects of sunlight falling across the surface of the land. Hill Shading estimates surface reflectance from the sun at any altitude and any azimuth. The reflectance is calculated in a range from 0 to 100.
  1. How should this data set be cited?

    U.S. Geological Survey, 2006, CAPENORTHSUN_MER4M.TIF: Image of the 4-m Sun-Illuminated Topography of the Sea Floor off Northeastern Cape Cod (Mercator): Open-File Report 2005-1048, U.S. Geological Survey, Coastal and Marine Geology Program, Woods Hole 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., 2006, 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, Coastal and Marine Geology Program, Woods Hole Science Center, Woods Hole, MA.

    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/bathymetry/sun_illum/mercator/capenorthsun_mer4m-thumb.gif> (GIF)
    Thumbnail image showing the extent and coverage of the data layer.
    <http://pubs.usgs.gov/of/2005/1048/data/bathymetry/sun_illum/mercator/capenorthsun_mer4m.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?

      The map projection used is Mercator.

      Projection parameters:
      Standard_Parallel: 41.650000
      Longitude_of_Central_Meridian: -70.316667
      False_Easting: 0.000000
      False_Northing: 0.000000

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 4.000000
      Ordinates (y-coordinates) are specified to the nearest 4.000000
      Planar coordinates are specified in meters

      The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview: There are no attributes associated with a GEOTIFF image.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  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 02543-1598
    USA

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

Why was the data set created?

To release a digital map (GeoTIFF image) derived from multibeam observations that shows sun-illuminated bathymetry at a spatial resolution of 4 m/pixel.

How was the data set created?

  1. From what previous works were the data drawn?

    98015_multibeam_data (source 1 of 1)
    Type_of_Source_Media: DVD-ROM
    Source_Contribution:
    The original multibeam bathymetric 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 2)
    (1) 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).

    (2) 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 (a SwathEd utility) with node spacings and scale selected by the operator. The grid file (capenorth.r4) was a floating point binary file.

    Person who carried out this activity:

    Bill Danforth
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    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.r4

    Date: Unknown (process 2 of 2)
    Using addSUN, the bathymetric raster files were generated using the mapped grid node information to depict the depth information in a shaded relief Mercator map. The shaded-relief image was generated using a sun elevation angle of 45 degrees from an azimuth of 0 degrees, and a vertical exaggeration of 4 times to emphasize sea floor features.

    Person who carried out this activity:

    Bill Danforth
    U.S. Geological Survey
    Geologist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598
    USA

    (508) 548-8700 x2274 (voice)
    (508) 457-2310 (FAX)
    bdanforth@usgs.gov

    Data sources used in this process:
    • capenorth.r4

    Data sources produced in this process:

    • capenorthsun_mer4m.tif

  3. What similar or related data should the user be aware of?

    Poppe, L.J., Foster, D.S., and Danforth, W.W., 2006, Character and distribution of exposed glaciodeltaic deposits off outer Cape Cod, Massachusetts, and their effects on hydrogeology and benthic habitats: Geo-Marine Letters v. 26, Springer, Germany.

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?

    Navigation was by differential GPS.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    All collected data were processed and used to produce this dataset.

  5. How consistent are the relationships among the observations, including topology?

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:
Data are not for navigational purposes.

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 02543-1598
    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

  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: 21-Mar-2006
Metadata author:
Lawrence J. Poppe
U.S. Geological Survey
Geologist
384 Woods Hole Road
Woods Hole, MA 02543-1598
USA

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

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.8.18 on Wed Mar 22 17:00:53 2006