Bedrock geologic map of the Grafton quadrangle, Worcester County, Massachusetts

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Frequently-anticipated questions:

What does this data set describe?

Title:
Bedrock geologic map of the Grafton quadrangle, Worcester County, Massachusetts
Abstract:
The bedrock geology of the 7.5-minute Grafton, Mass., quadrangle consists of deformed Neoproterozoic to early Paleozoic crystalline metamorphic and intrusive igneous rocks. The database includes contacts of bedrock geologic units, faults, outcrops, structural geologic information, and photographs. The digital data are intended for use by all government, academic, commercial, or other agencies in need of digital geologic map information.
Supplemental_Information:
Locational data were collected in latitude and longitude (degrees minutes seconds) in WGS84 datum, and reprojected to the State Plane Coordinate System currently in use in Massachusetts. The database is accompanied by a large format color map, an explanatory pamphlet, and a readme.txt file.
  1. How should this data set be cited?

    Walsh, Gregory J. , Aleinikoff, John N. , and Dorais, Michael J. , 2011, Bedrock geologic map of the Grafton quadrangle, Worcester County, Massachusetts: Scientific Investigations Map 3171, U.S. Geological Survey, Reston, Virginia.

    Online Links:

    Other_Citation_Details:
    Walsh, G.J., Aleinikoff, J.N., and Dorais, M.J., 2011, Bedrock geologic map of the Grafton quadrangle, Worcester County, Massachusetts: U.S. Geological Survey Scientific Investigations Map 3171, 1 sheet, scale 1:24,000, 39-p. text.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -71.750007
    East_Bounding_Coordinate: -71.624266
    North_Bounding_Coordinate: 42.250305
    South_Bounding_Coordinate: 42.124892

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 2005
    Ending_Date: 2011
    Currentness_Reference: publication date

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: Map

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • Complete chain (67)

    2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: State Plane Coordinate System 1983
      State_Plane_Coordinate_System:
      SPCS_Zone_Identifier: 2001
      Lambert_Conformal_Conic:
      Standard_Parallel: 41.716667
      Standard_Parallel: 42.683333
      Longitude_of_Central_Meridian: -71.500000
      Latitude_of_Projection_Origin: 41.000000
      False_Easting: 200000.000000
      False_Northing: 750000.000000

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.000100
      Ordinates (y-coordinates) are specified to the nearest 0.000100
      Planar coordinates are specified in meters

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.

  7. How does the data set describe geographic features?

    Entity_and_Attribute_Overview:
    The geologic data layers in the GIS database of this report include, 1) CONTACTS - Polygon and arc data layers of bedrock geologic map units, including a lithology attribute table, 2) EXPOSURE - Unattributed polygon data layer of bedrock outcrops examined in this study, 3) FOLDS - Axial traces of map scale folds, 4) PHOTOS - Field photographs of geology, 5) STRUCTURE - Point data of structural data.
    Entity_and_Attribute_Detail_Citation: <https://pubs.usgs.gov/sim/3171/Downloads/readme.txt>

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?

    U.S. Geological Survey
    c/o Gregory J. Walsh
    Geologist
    P.O. Box 628
    Montpelier, Vermont 05601
    USA

    802-828-4528 (voice)
    802-828-4465 (FAX)
    gwalsh@usgs.gov

Why was the data set created?

The bedrock geology was mapped to study the tectonic history of the area and to provide a framework for ongoing hydrogeologic characterization of the fractured bedrock of Massachusetts. The digital data are intended for use by all government, academic, commercial, or other agencies in need of digital geologic map information.

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: 2011 (process 1 of 1)
    Geology was mapped by Walsh at a scale of 1:24,000. Locational information was provided by GPS receiver. The line and polygon data were first compiled in Adobe Illustrator over registered scans of field sheets using the topographic base. Film positive separates of the published topographic base map were scanned at 400 dpi and registered in ArcMap. Illustrator files were converted to DXF vector files and imported to Arc/Info version 9.3. Point data were collected with GPS and attribute data with a hand-held 3COM Palm Pilot III PDA computer. Data from the PDA were converted to tab-delimited TXT files, joined with GPS coordinate data in ArcMap, saved as a shapefile, and exported into an Arc/Info coverage where point symbols were created and plotted. Line and polygon data were edited in Arc/Info and converted to shapefiles. Shapefiles were plotted in ArcMap and exported to Illustrator. Final cartography was done in Adobe Illustrator CS4.

    Person who carried out this activity:

    Gregory J. Walsh
    U.S. Geological Survey
    Geologist
    P.O. Box 628
    Montpelier, Vermont 05601
    USA

    802-828-4528 (voice)
    802-828-4465 (FAX)
    gwalsh@usgs.gov

    Hours_of_Service: 0900 to 1700 eastern standard time
    Data sources produced in this process:
    • Walsh and others (2011)

  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?

    All attributes digitized during the creation process were verified by displaying the lines and points in the database with respect to the USGS 7.5-minute topographic map, but no formal tests were performed.

  2. How accurate are the geographic locations?

    The data were created on a USGS 7.5-minute topographic map at 1:24,000 scale. Therefore, the horizontal accuracy is assumed to be within National Map Accuracy Standards, with a horizontal accuracy of 45.6 feet at the 95% confidence level. Locational information in the field was provided by a Garmin eTrex Venture GPS receiver or similar.

  3. How accurate are the heights or depths?

    The data were delineated on a USGS 7.5-minute topographic map at 1:24,000 scale. Therefore, the vertical accuracy is assumed to be within National Map Accuracy Standards, with a vertical accuracy of 11.9 feet at the 95% confidence level.

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

    The geologic contacts were delineated on USGS 7.5-minute topographic maps based on observations at the outcrops shown in the database. Not all outcrops within the area were identified or visited during mapping. The geologic contacts might change if additional outcrops are discovered or exposed as the natural land changes or as the result of development. The features in the database are not based on legal parcels or definitions.

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

    These data are believed to be logically consistent, though no tests were performed. Geometry is topologically clean.

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: none

  1. Who distributes the data set? (Distributor 1 of 1)

    U.S. Geological Survey - Information Services
    Box 25286, Denver Federal Center
    Denver, Colorado 80225
    USA

    1-888-ASK-USGS (voice)
    ask@usgs.gov

    Hours_of_Service: 0900 to 1700 mountain standard time
  2. What's the catalog number I need to order this data set?

    USGS Scientific Investigations Map 3171

  3. What legal disclaimers am I supposed to read?

    These data were prepared by an agency of the U.S. Government. Neither the U.S. Government, the Department of the Interior, nor the U.S. Geological Survey, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, 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 U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and/or contained herein. 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?

Who wrote the metadata?

Dates:
Last modified: 01-Jun-2011
Metadata author:
USGS
c/o Gregory J. Walsh
Geologist
P.O. Box 628
Montpelier, VT 05601
USA

802-828-4528 (voice)

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

Generated by mp version 2.9.8 on Wed Feb 15 11:18:20 2012