Lanfear, K.J. 19940816 Unknown 2.3.1 vector digital data Reston, Virginia, USA U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?county2m This coverage is of the county boundaries of the conterminous United States. It was derived from the Digital Line Graph (DLG) files representing the 1:2,000,000-scale map in the National Atlas of the United States. This coverage is intended as a basemap for a variety of applications. This series of maps was published as part of the National Atlas of the United States (USGS, 1970). The maps for the conterminous United States were digitized in 15 sheets and published in the Digital Line Graph (DLG) format as described by Domeratz and others (1983). Each sheet was prepared by reading the DLG files of the political and water bodies layers, converting them to ARC/INFO, extracting the county boundaries and the coastline, respectively, and joining the two layers together. FIPS codes were assigned to all polygons using available sources, and were checked manually. Boundaries with adjacent sheets of the 15-sheet set were edgematched manually, arbitrarily choosing one of the sheets as the "correct" border. Edgematching operations adjusted the linework as far as was necessary so that the coverages would fit to a tolerance of 100 meters. The coverage (referred to herein as Version 1.0) was stored as 49 separate coverages (48 states and the District of Columbia) because the ARC/INFO software in use at the time could not process the entire coverage. Individual states could be joined by specifying a tolerance of 100 meters. From time to time, adjustments were made to the state coverages to reflect changes in U.S. counties. It is believed the accuracy of these adjustments is comparable to the original linework. For Version 2.0, all state coverages were rejoined and manually edited to produce a perfect edgematch between all states. For states on the original map sheet boundaries, this adjustment averaged less than 20 meters and in no case was more than 100 meters. The whole coverage was CLEANed to a tolerance of 20 meters, which resulted in few, if any, effects on small offshore islands. The coverage also was checked to ensure that it represented current U.S. counties or county equivalents. The coverage in Version 1.0 stopped at the coastline. There was no attempt to depict offshore areas. The created some problems when the coverage was used to assign county codes to sampling stations located near the coast. To help in this matter, Version 2.o includes offshore extensions of the county polygons. The (water) boundaries of many of these polygons are arbitrary. The Canadian Great Lakes features are another new addition to Version 2.0. They were added to improve the utility of the coverage for visual displays. Although the Canadian Great Lakes are logically represented by a single polygon, practical considerations -- the inability of some software to plot polygons with a large number of vertices -- made it necessary to separate them into 4 polygons. The dividing lines are located in narrow channels to minimize interference with plotting patterns. Canadian islands within the Great Lakes also were included. All tics were relocated to places that are easily visible on maps of the United States, to help in registering maps that may not otherwise have adequate registration information. To expedite accessing parts of the coverage, certain items have been indexed with the procedure, index_county.aml. See Section 3. A spatial index also was created. When using this coverage to clip or intersect other coverages, a tolerance as low as 2 meters can be used. The processing used to derive this coverage moved boundaries from their positions on the original maps. In cases of conflicting lines, preference was given to forming the correct topology. Strictly speaking, this coverage is not identical to the source materials. These changes were unavoidable in producing a continuous coverage of the conterminous United States. For revision 2.1, it was necessary to alter about 100 arcs. This was accomplished with ARCEDIT using the 1:100,000 TIGER county coverage as a background. These arcs were matched to the background so that they matched at least as close as other arcs that were not edited. Related Spatial and Tabular Data Sets: This coverage is part of series of 1:2,000,000-scale basemaps covering the United States. Layers presently available in this set include: county2m -- County and state boundaries. waterbod2m -- Water Bodies. huc2m -- Hydrologic cataloging units (basins). Other References Cited: Domaratz, M. A., Hallam, C. A., Schmidt, W. E., and Calkins, H. W., 1983. USGS Digitral Cartographic Data Standards: Digital Line Graphs from 1:2,000,000-scale Maps. U.S. Geological Survey Circular 895-D, 38p. U. S. Geological Survey, 1970. National atlas of the United States of America: Washington D.C., U. S. Geological Survey, 417p. 19940819 publication date Complete As needed -128.07002717 -65.25698378 48.26194027 22.67774911 None county county equivalent Conterminous United States inlandWaters None The original files for this map were provided in 15 sections. Boundaries near the edges of sections have been adjusted in edgematching. Boundaries of polygons extending into the water (ocean or Great Lakes) should be considered arbitrary. U.S. Geological Survey mailing address

12201 Sunrise Valley Drive, MS 440

Reston VA 20192 USA 1-888-275-8747 h2oteam@usgs.gov Please use email. http://water.usgs.gov/GIS/browse/county2m.jpg illustration of data set jpg dgux, 5.4R3.10, AViiON UNIX, ARC/INFO version 7.0.4 See supplemental information. See supplemental information. See supplemental information. 19940819 Version 2.3.1 Corrected 2 errors reported for version 2.3 -- 1. Removed a duplicate label in the water polygon for Hampton, VA, FIPS 51650. 2. Corrected the PLYTYPE attribute to PLYTYPE=9 for the external polygon. Because this had been set to 0 in some prior processing, the BNDTYPE values for outside arcs were not correct. Ran index_county.aml to correct the BNDTYPE values, 19980306 Vector Point 5064 String 12374 GT-polygon composed of chains 5064 Albers Conical Equal Area 29.5 45.5 -96 23 0.0 0.0 coordinate pair 1.0 1.0 meters COUNTY2M.PAT Polygon Attribute Table n/a AREA Area of polygon in square coverage units Computed Positive real numbers n/a n/a PERIMETER Perimeter of polygon in coverage units Computed Positive real numbers n/a n/a COUNTY2M# Internal feature number Computed Sequential unique positive integer n/a n/a COUNTY2M-ID User-assigned feature number User-defined Integer n/a n/a FIPS County code Federal Information Processing Standard 01001-56999, none = 0 n/a n/a ST State abbreviation U.S. Postal Service AL ... WY, none = blank n/a n/a CNTYNAME County name U.S. Geological Survey files Upper-case alphanumeric n/a n/a PLYTYPE Polygon type See narrative. 0-4, and 9. n/a n/a WORKB Working field none any integer n/a n/a FIPSST State code Federal Information Processing Standard 01-56, none = 0 n/a n/a FIPSCNTY County code, within state Federal Information Processing Standard 001-999 n/a n/a COUNTY2M.AAT Arc attribute table ARC/INFO file FNODE# Internal number of from-node Computed Sequential unique positive integer n/a n/a TNODE# Internal number of to-node Computed Sequential unique positive integer n/a n/a LPOLY# Internal number of polygon to left of arc Computed Sequential unique positive integer n/a n/a RPOLY# Internal number of polygon to right of arc Computed Sequential unique positive integer n/a n/a LENGTH Length of arc in coverage units Computed Positive real numbers n/a n/a COUNTY2M# Internal feature number Computed Sequential unique positive integer n/a n/a COUNTY2M-ID User-assigned feature number User-defined Integer n/a n/a BNDTYPE Boundary type See narrative 0-9 n/a n/a COUNTY2M.FIPS_LIST List of county codes used in coverage. From COUNTY2M.PAT FIPS County code From COUNTY2M.PAT (FIPS) n/a n/a WORKB Working variable n/a Local n/a n/a COUNTY2M.AML_INDEX AML listing for indexing U.S. Geological Survey LINE Line of code U.S. Geological Survey text n/a n/a Each county is identified by a 5-digit Federal Information Processing Standard (FIPS) code. The first 2 digits represent the state and the 3 remaining represent the county within state. County names (in upper case) and the two-character state abbreviation also are included. All polygons are coded by polygon type (PLYTYPE) as follows: 0 = U.S. land. 1 = Extensions of counties into the ocean and estuaries. Some boundaries may be arbitrary. 2 = U.S. Great Lakes. Some boundaries between counties may be arbitrary. 3 = Canadian Great Lakes. 4 = Canadian islands in Great Lakes, included for visual cartographic purposes. 9 = External polygon. All arcs are coded by boundary type (BNDTYPE) as follows: 0 = Coastline of United States. 1 = State-state border occurring on land. 2 = County-county border, within state, occurring on land. 3 = State-state border occurring on the ocean, an estuary, or a Great Lake. Some of these borders are arbitrary. 4 = County-county border, with state, but occurring on the ocean, an estuary, or a Great Lake. Some of these borders are arbitrary. 5 = International border occurring on land. 6 = International border occurring on water. 7 = Canadian shoreline of the Great Lakes. 8 = Arbitrary separation line between the Canadian portions of the Great Lakes. 9 = Closure line with the external polygon. This is arbitrary. All BNDTYPE values are determined from the adjoining polygons by the routine, INDEX_COUNTY.AML. The coverage is indexed (ARC: INDEXITEM) on FIPS code, state FIPS code, state abbreviation, county name, polygon type, and boundary type. The listing for INDEX_COUNTY.AML, if not available on the system, can be found in COUNTY2M.AML_INDEX. See overview. U.S. Geological Survey Ask USGS - Water Webserver Team mailing

445 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://water.usgs.gov/user_feedback_form.html Although this data set has been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, 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. Export Full coverage, version 2.3.1 zipped 48 http://water.usgs.gov/GIS/dsdl/county2m.e00.gz SDTS Full coverage, version 2.3.1 zipped 41 http://water.usgs.gov/GIS/dsdl/county2m.sdts.tgz Export Version 2.3 (old) zipped 48 http://water.usgs.gov/GIS/dsdl/county2m_21.e00.gz SDTS Version 2.3 (old) zipped 41 http://water.usgs.gov/GIS/dsdl/county2m_21.sdts.tgz None. This dataset is provided by USGS as a public service. 20041108 U.S. Geological Survey Ask USGS -- Water Webserver Team mailing

445 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+county2m FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998