Hitt, Kerie J. 20031124 Version 1 map http://water.usgs.gov/lookup/getspatial?uspopd00x10g This data set represents 2000 population density by block group as a 100-m grid using data from the 2000 Census of Population and Housing. The demographic data is from CensusCD 2000 Short Form Blocks published by GeoLytics, E. Brunswick, NJ, which uses the 2000 Census Summary File 1 (SF 1). Grid cell values represent population density in people per square kilometer multiplied by 10 so that the data could be stored as integer. This is one of the ancillary GIS data layers developed to characterize USGS National Water-Quality Assessment (NAWQA), http://water.usgs.gov/nawqa/, sampling sites for national synthesis of water-quality data. The ArcInfo Workstation grid is stored in the uspopd00x10g.tgz file (gzipped tar file). The uncompressed file size of uspopd00x10g.tar is about 55MB. Ways to extract the grid from the .tgz archive file include TARARC, Winzip, UnStuffIt, or the following GNU utilities for WIN32: >gunzip uspopd00x10g.tgz >tar xvof uspopd00x10g.tar The grid "uspopd00x10g" will be in a subdirectory called arctar00000. The data set is provided in 4 tiles in gzipped ASCII format--one for each quadrant of the country (NW,NE,SW,SE)--in addition to the native ArcInfo Workstation grid format. The ASCII files are provided as a nonproprietary format in case the user's software cannot access the data in ArcInfo Workstation grid format. The text files store the gridded population data in 4 files because in text format, a single file would be larger than 2.1 gigabytes in size, which is a hard file size limit for most 32-bit operating systems. The ASCII files are gzipped as uspopd00x10nw.txt.gz, uspopd00x10ne.txt.gz, uspopd00x10se.txt.gz, and uspopd00x10sw.txt.gz. Uncompressed file sizes of the ASCII files are: >uspopd00x10nw.txt 863127948 bytes (northwest quadrant of U.S.) >uspopd00x10ne.txt 1516894048 bytes (northeast quadrant of U.S.) >uspopd00x10sw.txt 1430219980 bytes (southwest quadrant of U.S.) >uspopd00x10se.txt 1809727455 bytes (southeast quadrant of U.S.) Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee (FGDC)-compliant file of metadata is intended to document the data set in nonproprietary form, as well as in ArcInfo format, this metadata file includes some ArcInfo-specific terminology. ArcInfo is part of the ArcGIS geographic information system software by ESRI, Redlands, California, http://www.esri.com. 2000 The data set is intended to represent conditions for the early 2000's. Complete No updates are planned unless errors or updates in the data occur. -127.975560 -65.255208 51.647982 22.768228 None Population Population density Demographic data Summary File 1 SF 1 Census 2000 Census short form inlandWaters none Conterminous United States The data in GeoLytics products is not public domain. It remains the copyrighted property of GeoLytics. Any "for profit" use of the data is prohibited. You may cite the data in a publication as long as you cite GeoLytics as the source. The data in GeoLytics products is not public domain. It remains the copyrighted property of GeoLytics. Any "for profit" use of the data is prohibited. You may cite the data in a publication as long as you cite GeoLytics as the source. http://water.usgs.gov/GIS/browse/uspopd00x10g.gif 28KB GIF image showing overview of 2000 population density data GIF This data set is based on demographic data from GeoLytics, E. Brunswick, NJ: GeoLytics CensusCD 2000 Short Form Blocks. Microsoft Windows 2000 Version 5.1 (Build 2600) Service Pack 1; ARC 8.3 Spot checked with 100-m grid of 1990 population density. Visual checks. GeoLytics 2001 1.0 proprietary digital data CensusCD 2000 Short Form Blocks E. Brunswick, NJ GeoLytics, Inc. http://www.geolytics.com/census2000.htm digital files on CDROM 2000 2000 Census of Population and Housing CensusCD 2000 Short Form Blocks This source provided the tabular population and land area data used in calculating the population density for each block group. Population density in people per square kilometer was calculated from the tabular input data as pop2000 / (arealand / 1000000), where arealand is square meters. The population data are keyed to the block group boundaries using a block group identifier code. The GeoLytics product contains all Census Short Form demographic data for over 8 million blocks from the 2000 U.S. Census of Population and Housing Summary File 1 (SF 1). Summary File 1 (SF 1) contains the 100-percent data, which is the information compiled from the questions asked of all people and about every housing unit. The GeoLytics product provided software to extract the population and housing unit data of interest in a format that could be imported into ArcInfo. U.S. Bureau of the Census, Geography Division 200101 1.0 digital data Cartographic boundary Files Block groups http://www.census.gov/geo/www/cob/bg2000.html digital files retrieved 8/20/2002 2000 2000 Cartographic boundary files This source provided the generalized block group boundaries. The block group boundaries are keyed to the population density data using a block group identifier code. The block group boundaries were converted from polygon format to grid format. The cartographic boundary files are a generalized extract from the U.S. Census Bureau's TIGER database. Line simplification/smoothing was performed with a tolerance of 0.005 decimal degrees and a coordinate reduction using the Douglas-Peucker method with a tolerance of 0.0003 decimal degrees. Very small polygons were eliminated when the combination of geographic codes existed elsewhere. The geography was clipped back to the shoreline of the United States, in contrast to TIGER/Line which shows the full extent of geography out to the 3-mile limit. Users of demographic data would need these boundaries or another set of block group boundaries such as the TIGER files to spatially represent the demographic data. The population data is referenced to the block group boundary by the block group identifier. The generalized files have a much smaller file size than the original file extraction from the Census Bureau's TIGER database, resulting in faster download and processing times. The cartographic boundary files are primarily designed for small scale, thematic mapping applications at a target scale range of 1:500,000 to 1:5,000,000. Because of coordinate thinning: >1. Cartographic boundary files should not be used for geocoding; >2. Some offshore, redundant, zero population and housing land > areas may be absent from the cartographic boundary files; >3. Cartographic boundary files are not necessarily vertically > integrated with previous boundary file sets. Created 4 regional grids of population density because creating one large floating-point grid was impossible. A national floating-point grid would have exceeded ArcInfo Workstation grid size limits of 2.1 gigabytes. However, ArcInfo Workstation stores integer format grids using run-length compression. This allows data to be stored in a single integer grid data set smaller than the 2.1 GB file size limit. The gridding procedure was specified to grid the data with a cell size of 100 meters and to give each cell the integer value of population density times 10. The following ArcInfo Workstation GRID commands create a regional grid for "region 4." >relate add pop00.rel >p >uspop00.dat >info >bgi >bgi >ordered >rw >~ >setcell 100 >setwindow -2489750,1765250,-75250,3281750 >/*POLYGRID converts data associated with polygon features to > grid cell format using the population density values > assigned to the polygons. >/*INT converts input floating-point values to integer > values on a cell-by-cell basis within the analysis window. >/*Adding .5 to the INT expression causes the integer numbers to be > rounded instead of truncated. >/* >usg4 = int ( polygrid (usbgalb,p//pdens) * 10 + .5 ) 20020826 Merged the 4 regional grids into 1 integer grid for the conterminous United States. >USPOPD00G = merge(usg1,usg2,usg3,usg4) 20020826 The merged national grid was too big to convert to an image for distribution. Instead, in case the user's software cannot access the data in ArcInfo Workstation grid format, the data was converted back into 4 regional grid tiles, one for each quadrant of the country. The 4 regional grids then were converted to ASCII files containing rows of data corresponding to the grid cells. For example, >setwindow -2489750,1765250,-75250,3281750 >uspopd4 = uspopd00x10g >gridascii uspopd4 uspopd00x10se.txt Here are the boundaries of the 4 regional grids/ASCII files: >NORTHWEST >West_Bounding_Coordinate: -128.18 >East_Bounding_Coordinate: -98.18 >North_Bounding_Coordinate: 51.58 >South_Bounding_Coordinate: 36.82 > >NORTHEAST >West_Bounding_Coordinate: -98.74 >East_Bounding_Coordinate: -65.28 >North_Bounding_Coordinate: 51.60 >South_Bounding_Coordinate: 37.11 > >SOUTHWEST >West_Bounding_Coordinate: -123.34 >East_Bounding_Coordinate: -97.83 >North_Bounding_Coordinate: 39.96 >South_Bounding_Coordinate: 23.15 > >SOUTHEAST >West_Bounding_Coordinate: -98.30 >East_Bounding_Coordinate: -69.93 >North_Bounding_Coordinate: 39.98 >South_Bounding_Coordinate: 23.40 20031105 Incorporated review comments from Curtis Price and LaRue Smith into metadata. 20031106 Katia Segre Cohen (GeoLytics) reviewed the metadata and gave permission for us to publish the population density data set (email from Katia Segre Cohen, dated 11/14/2003). 20031114 Raster Grid Cell 29183 46253 1 Albers Conical Equal Area 29.5 45.5 -96 23 0.00000 0.00000 coordinate pair 100.0 100.0 Meters North American Datum of 1983 GRS1980 6378137.0 298.257222 The value of each 100-m grid cell is the population density in persons per square kilometer multiplied by 10 and rounded to the nearest integer to take advantage of ArcInfo integer grid compression. (A floating point grid would have exceeded the maximum file size allowed by 32-bit software applications.) The Census definition of urbanized area is 1000 persons per square mile or about 386 persons per square kilometer. That translates in this data set as an urban cutoff of about 3860 (386.0 persons per square kilometer multiplied by 10). Population density was calculated at the block group level (not at the grid cell level) originally as: >PPERKM2 = POP00 / (AREALAND / 1000000) where AREALAND is square meters. The ArcInfo Workstation grid has no .VAT (value attribute table), but it does have a .STA (statistics file): > COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC > 1 MIN 8 15 F 3 > 9 MAX 8 15 F 3 > 17 MEAN 8 15 F 3 > 25 STDV 8 15 F 3 > >MIN is the minimum value in the grid (0). >MAX is the maximum value in the grid (1284899). >MEAN is the arithmetic mean of the values in the grid. >STDV is the standard deviation of the values in the grid. The ASCII files of data are provided in case the user's software cannot access the data in ArcInfo Workstation grid format. Each of the ASCII files consists of a 6-line header followed by population values in row-major order. Row 1 of the data is at the top of the grid, row 2 is just below row 1, and so forth. Each row of data ends with a carriage return. >NCOLS xxx (number of columns) >NROWS xxx (number of rows) >XLLCORNER xxx (x coordinate of lower left corner of grid) >YLLCORNER xxx (y coordinate of lower left corner of grid) >CELLSIZE 100 (100 x 100 meter cells) >NODATA_VALUE -9999 (cells with no data are coded as -9999) >row 1 (cell values for row 1) >row 2 (cell values for row 2) >... >row n (cell values for last row) The projection parameters are: >Projection ALBERS >Datum NAD83 >Zunits NO >Units METERS >Spheroid GRS1980 >Xshift 0.0000000000 >Yshift 0.0000000000 >Parameters > 29 30 0.000 /* 1st standard parallel > 45 30 0.000 /* 2nd standard parallel >-96 0 0.000 /* central meridian > 23 0 0.000 /* latitude of projection's origin >0.00000 /* false easting (meters) >0.00000 /* false northing (meters) Census Bureau U.S. Geological Survey Ask USGS - Water Webserver Team mailing

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Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+uspopd00x10g 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. Grid Full coverage zipped 1 http://water.usgs.gov/GIS/dsdl/uspopd00x10g.tgz Other Text file zipped 1 http://water.usgs.gov/GIS/dsdl/uspopd00x10ne.txt.gz Other Text file zipped 1 http://water.usgs.gov/GIS/dsdl/uspopd00x10nw.txt.gz Other Text file zipped 1 http://water.usgs.gov/GIS/dsdl/uspopd00x10se.txt.gz Other Text file zipped 1 http://water.usgs.gov/GIS/dsdl/uspopd00x10sw.txt.gz None. This dataset is provided by USGS as a public service. 20041108 U.S. Geological Survey Ask USGS -- Water Webserver Team mailing

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Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+uspopd00x10g FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998