| Census Blocks of Loudoun County, VA (2000) | |
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Data format: SDE Feature Class File or table name: GISDBB.GISBROW.CENSUS2000_BLOCKS_POLY Coordinate system: Lambert Conformal Conic Theme keywords: boundary, Census, boundaries, demographic, block, society, boundaries |
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Abstract:
This GIS layer contains the geographical boundaries of the 2000 census blocks for Loudoun County, Virginia. The 2000 census block boundaries were used for statistical data collection and tabulation purposes for the 2000 Decennial Census. Census blocks are the smallest geographic area for publishing data from the decennial Census. There are no population size requirements for census blocks. The geographical area covered by this geographic feature class is generally very small in densely settled areas, for instance one city block. In sparsely settled areas they may cover several square miles. Census blocks nest within every 2000 Census geographic area (i.e. block groups, tracts, census designated places, and local, state, and federal election districts). This nesting of blocks allows Census Bureau statistical data to be tabulated to the appropriate geographic areas by aggregating the block data up. Census blocks are uniquely numbered within census tracts, with the blocks valid range being 1 to 9999 with leading zeros added (i.e. 0001, 0023) when necessary to create a four digit unique identifier.
This 2000 Census block layer is based on the U.S. Census Bureau Census 2000 TIGER/Line files. The boundaries are an extract of aerial photography and cartographic information, such as roads and streams, from the Loudoun County GIS system. Census Blocks are bounded on all sides by visible features, such as roads, streams, lakes, power lines, and railroad tracks, and/or by non-visible boundaries such as town and county boundaries, and short line-of-sight extensions of streets and roads. |
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Metadata elements shown with blue text are defined in the Federal Geographic Data Committee's (FGDC) Content Standard for Digital Geospatial Metadata (CSDGM). Elements shown with green text are defined in the ESRI Profile of the CSDGM. Elements shown with a green asterisk (*) will be automatically updated by ArcCatalog. ArcCatalog adds hints indicating which FGDC elements are mandatory; these are shown with gray text.
This GIS layer contains the geographical boundaries of the 2000 census blocks for Loudoun County, Virginia. The 2000 census block boundaries were used for statistical data collection and tabulation purposes for the 2000 Decennial Census. Census blocks are the smallest geographic area for publishing data from the decennial Census. There are no population size requirements for census blocks. The geographical area covered by this geographic feature class is generally very small in densely settled areas, for instance one city block. In sparsely settled areas they may cover several square miles. Census blocks nest within every 2000 Census geographic area (i.e. block groups, tracts, census designated places, and local, state, and federal election districts). This nesting of blocks allows Census Bureau statistical data to be tabulated to the appropriate geographic areas by aggregating the block data up. Census blocks are uniquely numbered within census tracts, with the blocks valid range being 1 to 9999 with leading zeros added (i.e. 0001, 0023) when necessary to create a four digit unique identifier. This 2000 Census block layer is based on the U.S. Census Bureau Census 2000 TIGER/Line files. The boundaries are an extract of aerial photography and cartographic information, such as roads and streams, from the Loudoun County GIS system. Census Blocks are bounded on all sides by visible features, such as roads, streams, lakes, power lines, and railroad tracks, and/or by non-visible boundaries such as town and county boundaries, and short line-of-sight extensions of streets and roads.
Census blocks are used in demographic analyses of Loudoun County. They are also used during the redistricting process to define local, state, and federal election boundaries. Blocks give the most detailed picture of the demographics within a given area.
The 2000 Census block layer has been modified from the Census Bureau's Tiger line file. Users should be aware that the Census's Tiger line data is devised from a mix of national and local GIS data sets. When the Tiger line data is overlaid with Loudoun County Government's detailed GIS layers it can be determined that the Census Bureau's Tiger line boundaries in some cases are slightly off from the actual location of the physical features, natural features, and governmental units such as town boundaries that they are designated to follow. The 2000 Loudoun Census block layer was generated by Loudoun County so that the block boundaries would overlay with the features in Loudoun County's GIS data sets that the boundary are designated to follow. Data are stored in the corporate ArcSDE Geodatabase as a polygon feature class. The coordinate system is Virginia State Plane (North), Zone 4501, datum NAD83 HARN (vertical datum, if applicable, NAVD88), US Survey foot units.
publication date
Every reasonable effort has been made to assure the accuracy of these data. Loudoun County, Virginia does not assume any liability arising from the use of these data. These data are provided without warranty of any kind, expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular service. Reliance on these data is at the risk of the user. These data were generated for use by Loudoun County and are available to the public. These data are intended for use at 1:2400 scale or smaller. Acknowledgement of Loudoun County would be appreciated in products derived from this data.
803 Sycolin Rd, Suite 104
MS 61
Retention of attribute accuracy throughout the personal geodatabase or shapefile to ArcSDE geodatabase feature class coversion process was ensured by a manual or automatic QA/QC programmatic check. To meet satisfactory QA/QC requirements the input coverage and output feature class must have, on a record by record basis, identical attribution when comparing all concatenated fields to all the user-defined attribution.
Topologically clean
Features may have been eliminated or generalized due to scale and intended use. To assist Loudoun County, Virginia in the maintenance of the data, please provide any information concerning discovered errors, omissions, or other discrepancies found in the data.
Retention of coordinate accuracy throughout the personal geodatabase or shapefile to ArcSDE geodatabase feature class conversion process was ensured by a manual or automatic QA/QC programmatic check. To meet satisfactory QA/QC requirements the input coverage and output feature class must have the same record total, and on a record by record basis, area, perimeter, and length differential of less than +/- 0.5%.
Provided the foundation upon which census blocks were drawn. The 2000 census blocks were the basis for digitizing the block boundaries.
Demographic data source for population, housing units, and households for census blocks
Census block shapefile downloaded from the U.S. Census Bureau. Overlaid the Census Bureau shapefile with with Loudoun County Government's detailed GIS layers to determine the actual location of the physical features, natural features, and governmental units such as town boundaries that the census blocks are designated to follow. Digitized lines using Loudoun County Government's detailed GIS layers.
Internal feature number.
ESRI
Feature geometry.
ESRI
Federal Information Processing State and County Code. It is a five digit code that identifies the state and county of the census block. The first two digits designate the state and are the state FIPS code. The last three digits designate the county and are the County FIPS code.
Loudoun County
Identifies the census tract that the block is within.
Loudoun County
One digit number that identifies the census block group within a census tract as designated by the U.S. Census Bureau. It is the first digit of the four digit identifying number of a census block within a tract.
Loudoun County
Four digit number that identifies the census block within a census tract as designated by the U.S. Census Bureau..
Loudoun County
The federal information process codes.
Loudoun County
population of the block.
Loudoun County
housing unit count of the block
Loudoun County
Source that updated feature class
Loudoun County
Date feature class created or modified.
Loudoun County
Not for public distribution. Internal User ID of editor creating or modifying feature class.
Loudoun County
Feature problem type identified during digitizing
Loudoun County
Area of census block in internal units
Loudoun County
Perimeter of census block in internal units
Loudoun County
BL_FIPSSTCO: Federal Information Processing State and County Code
51107 - Virginia (51) and Loudoun County (107)
BL_UPD_SOURCE: Source that updated feature class
Source Description 0 Unknown 1 Legacy 2 County 3 Contract
PROB_TYPE: Feature problem type identified during digitizing
Value Description 1 Complete Match, not skewed (census block data coincident with Loudoun County data) 2 Complete Match, skewed (census block data not coincident) 3 Complete Match using Street Mast (census bock data may or may not have been coincident) 4 Mostly Complete Match, Partial line completed (small portion of one line segment drawn by editor) 5 Mostly Complete Match, Whole line completed (large portion of one line segment drawn by editor) 6 Partially Complete Match, Multiple Line Completeion (Various multiple line segments drawn by editor) 7 Census Based (block built by census data only, no Loudoun County data support) 8 Other (Refer to write-up in desciptions field of CensusProblemLog databases' table)
1 Harrison Street S.E., 2nd floor
MS 65
Every reasonable effort has been made to assure the accuracy of these data. Loudoun County, Virginia does not assume any liability arising from the use of these data. These data are provided without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular service. Reliance on these data is at the risk of the user.
ESRI Personal Geodatabase Feature Class
ESRI Shapefile
AutoCad Digital Exchange File
Size limit: 4.5 GB. Visit our website at: http://www.loudoun.gov/omagi, click on "Loudoun County Mapping Documents & Order Forms." The "Forms" directory will lead you to custom & standard (countywide) data order forms. Hardcopy maps may also be available; please contact the Mapping Office Public Information Counter for more information regarding all data requests.
1 Harrison Street SE, 2nd Floor
MS 65