Quadrangle Geologic Maps
Information about Our Digital Quadrangle Geologic Map Series ( index map is available at the bottom of this page ).
MGS is developing digital geologic maps, particularly for use in geographic information systems (GIS). These maps are available for purchase on CD-ROM, and printed versions are available separately. Print versions are full-color, full-scale paper plots at a resolution of 300 dpi (generally about 34 x 44 inches in size). To purchase copies of maps (paper or CD-ROM) contact the Publications Office with the Version number and Title from the chart below. If you are interested in our traditional paper map products see the Maps section of the online List of Publications for ordering information and prices.
All maps and geospatial data are projected in the Maryland State Plane coordinate system (Lambert conformal conic projection) North American Datum 1983 (NAD83) meters. The geologic information for the quadrangle maps is compiled at a scale of 1:24,000 (1 inch equals 2,000 feet). The base maps for this series were developed from U.S. Geological Survey topographic 7.5-minute quadrangle maps (1:24,000 scale). Contour intervals are in feet.
The CDs contain a copy of the pertinent map(s) in Adobe Acrobat PDF format. If you have access to a large-format color printer you could print these maps at full scale from the PDF file. The CDs also contain files for use in GIS. The GIS files were created using software (version 8.2 or higher). ArcGIS coverages as well as interchange files (.e00) are provided for the vector layers, which include the geologic layers and some or all of the base map layers. Some maps contain raster images for some base map components; rasters are in TIFF format. The full written descriptions of the geologic units are provided in a text file format in addition to being on the PDF. Text files can be read by any text reader (such as Notepad, Wordpad, or Microsoft Word). Metadata files (information about the map and how the layers were made) are provided as part of the digital layers and as separate text files.
Information about ESRI’s ArcExplorer software is provided on the CD but must be downloaded separately. ArcExplorer is ESRI's free GIS data reader software (for use with coverages, shapefiles, images). Visit the ESRI website at http://www.esri.com/software/arcexplorer/index.html to download the software or get more information about this program.
Older quadrangles are commonly available only as image files (JPEG) scanned from paper maps.