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.
This is a Vector data set. It contains the following vector data types (SDTS terminology):
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.
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.
Person who carried out this activity:
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.
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.
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.
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.
These data are believed to be logically consistent, though no tests were performed. Geometry is topologically clean.
Are there legal restrictions on access or use of the data?
- Access_Constraints: none
- Use_Constraints: none
USGS Scientific Investigations Map 3171
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.
|Data format:||Geologic units and structural features in format Arc/Info export (version 9.3)|
|Data format:||Geologic units and structural features in format Shapefile (version 1.0)|