Geologic Map Database of the Washington DC Area Featuring Data From Three 30 X 60 Minute Quadrangles: Frederick, Washington West, and Fredericksburg

Online link	https://geo-nsdi.er.usgs.gov/metadata/open-file/01-227/metadata.faq.html
Description	The Washington DC Area geologic map database (DCDB) provides geologic map information of areas to the NW, W, and SW of Washington, DC to various professionals and private citizens who have uses for geologic data. Digital, geographically referenced, geolo
Originators	Davis, Adam M.; Southworth, C. Scott; Schindler, J. Stephen; and Reddy, James E.
Publication	U.S. Geological Survey Open-File Report 01-227

States or counties

Arlington, Berkeley, Caroline, Carroll, Charles, Clarke, Culpeper, Essex, Fairfax, Fauquier, Frederick, Hanover, Howard, Jefferson, King George, Loudoun, Louisa, Montgomery, Orange, Prince George's, Prince William, Rappahannock, Spotsylvania, Stafford, Washington, Westmoreland, District of Columbia

arcs

Characteristic of the arc features in coverage csgeol are coded in csgeol.aat, the arc attribute table. The .aat consists of the following items: ARC-CODE and LINETYPE

Label	Definition
`arc-code`	Arc-code is a positive integer value (3 3 I) item in the arc attribute table. Values range from 0 to 99. Arc-code describes the stratigraphic boundary, fault, or other linear feature. The code is described by the item LINETYPE.

polygons

Characteristic of the polygon features are coded in the polygon attribute table. Table csgeol.pat includes of the following items: CLASS, UNIT (geologic unit label), and UNITTYPE (geologic unit).

Label	Definition
`class`	Class is a positive integer value (4 5 B) item in the polygon attribute table. Values range from 102 to 1170. The table csgeol.lut contains class and the corresponding geologic label. See USGS Open-File Report 00-192 for full descriptions of the geologic units.

points

Characteristic of point features in coverage cssstruct are coded in csstruct.pat, the point attribute table. The .pat includes the following items: ANGLE, DIP, CODE, and POINTTYPE.

Label	Definition
`angle`	Angle is a positive integer value (3 3 I) item in the point attribute table. Values may range from 0 to 360 degrees. The value is the azimuthal measurement of strike, where North is 0 degrees and values increase clockwise.
`dip`	Dip is a positive integer value (3 3 I) in the point attribute table. Values may range from 0 to 90 degrees.
`code`	Code is a positive integer value (3 3 I) item in csstruct.pat. It is a coded value representing the type of structure measured. Item pointtype is a text field which describes the type of measurement.