Traffic Analysis Zones (TAZ) of Loudoun County, Virginia (2012)

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Metadata:

Identification_Information
Data_Quality_Information
Spatial_Data_Organization_Information
Spatial_Reference_Information
Entity_and_Attribute_Information
Distribution_Information
Metadata_Reference_Information

Identification_Information:

Citation:

Citation_Information:

Originator: Loudoun County, VA, Department of Planning
Publication_Date: 20120119
Title: Traffic Analysis Zones (TAZ) of Loudoun County, Virginia (2012)
Geospatial_Data_Presentation_Form: vector digital data

Description:

Abstract:: This GIS layer contains the geographical boundaries of the Metropolitan Washington Council of Government's Traffic Analysis Zones (TAZ) of Loudoun County, Virginia. The TAZ boundaries are used for statistical data tabulation purposes and local and Washington, D.C. regional planning purposes. TAZs are designed to be relatively homogeneous units with respect to population, economic, and transportation characteristics. These TAZ boundaries were delineated by Loudoun County Government and adopted by the Metropolitan Washington Council of Governments. The Round 8.0 demographic forecasting round of 2010 was the first forecasting series to use these boundaries. TAZ boundaries remain unchanged for a period of about ten to fifteen years.
Purpose:: Traffic Analysis Zones (TAZ) are used for demographic analyses of Loudoun County, as well as for Loudoun County and Washington, D.C. regional planning purposes. TAZs are also used extensively for transportation modeling and transportation planning. TAZs are used to gain a detailed picture of population, housing, and employment, within a given area. The TAZ boundaries are used for statistical data tabulation purposes, including the MWCOG cooperative forecasting rounds. TAZs are used to gain a detailed picture of population, housing, and employment, within a given area. The Round 8.0 demographic forecasting round of 2010 was the first forecasting series to use these boundaries. Forecasts for the TAZs are produced by Loudoun County by accounting for regional and local market trends, zoning, planned land use, and the long-range supply of land.
Supplemental_Information:: Loudoun County's Traffic Analysis Zones (TAZ) were delineated by Loudoun County Government in cooperation with the Metropolitan Washington Council of Governments (MWCOG). The TAZ layer has been modified from the MWCOG TAZ GIS layer. When the MWCOG GIS layer is overlaid with Loudoun County Government's detailed GIS layers it can be determined that the MWCOG TAZ 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 Loudoun TAZ layer was generated by Loudoun County so that the TAZ boundaries would overlay with the features in Loudoun County's GIS data sets that the boundaries are designated to follow. The forecasts for the TAZs are updated by Loudoun County generally once every year to account for changes in market conditions, rezonings, and comprehensive plan amendments. The TAZ boundaries remain unchanged for a period of about ten to fifteen years. 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.

Status:

Progress: Complete
Maintenance_and_Update_Frequency: Irregular

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -77.963439
East_Bounding_Coordinate: -77.323973
North_Bounding_Coordinate: 39.326230
South_Bounding_Coordinate: 38.844263

Keywords:

Theme:

Theme_Keyword_Thesaurus: none; Employee generated
Theme_Keyword: housing units
Theme_Keyword: traffic
Theme_Keyword: forecast
Theme_Keyword: boundaries
Theme_Keyword: household
Theme_Keyword: region
Theme_Keyword: population
Theme_Keyword: boundary
Theme_Keyword: demographic
Theme_Keyword: TAZ
Theme_Keyword: COG

Theme:

Theme_Keyword_Thesaurus: ISO 19115 Topic Categories
Theme_Keyword: society
Theme_Keyword: boundaries

Place:

Place_Keyword_Thesaurus: none; Employee generated
Place_Keyword: Virginia
Place_Keyword: DC
Place_Keyword: County
Place_Keyword: 51107
Place_Keyword: D.C.
Place_Keyword: Washington
Place_Keyword: Loudoun

Access_Constraints: None

Use_Constraints:

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.

Point_of_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA, Department of Planning

Contact_Position: Demographer

Contact_Address:

Address_Type: mailing and physical
Address: 1 Harrison St, SE
Address: MS 62
City: Leesburg
State_or_Province: VA
Postal_Code: 20175
Country: US

Contact_Voice_Telephone: (703) 777-0246

Contact_Facsimile_Telephone: (703)777-0441

Contact_Electronic_Mail_Address: dop@loudoun.gov

Hours_of_Service: 8:30-5:00 EST, M-F

Native_Data_Set_Environment:

Microsoft Windows Server 2008 Version 6.0 (Build 6002) Service Pack 2; ESRI ArcGIS 10.0.5.4400

Data_Quality_Information:

Attribute_Accuracy:

Attribute_Accuracy_Report:: 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.

Logical_Consistency_Report: Topologically clean

Completeness_Report:

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.

Positional_Accuracy:

Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:: 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%.

Lineage:

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20100401
Title: 2010 Census SF1 block data

Type_of_Source_Media: onLine

Source_Citation_Abbreviation: 2010 Census SF1 block data

Source_Contribution:

The 2010 Census SF1 block data were the basis for deriving the demographic data.

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20100111
Title: ESRI Tiger files

Type_of_Source_Media: None

Source_Citation_Abbreviation: ESRI Tiger files

Source_Contribution:

TIGER/Line files provided the foundation upon which census blocks were drawn. The 2010 Census blocks were the basis for devising the TAZ boundaries.

Source_Information:

Type_of_Source_Media: None
Source_Contribution:: Loudoun County Government GIS digitized block lines for aligning TAZ data with Loudoun County GIS data

Source_Information:

Source_Citation:

Citation_Information:

Originator: Loudoun County Department of Planning
Publication_Date: 20120102
Title: Loudoun County Department of Planning
Geospatial_Data_Presentation_Form: spreadsheet

Type_of_Source_Media: hardcopy

Source_Citation_Abbreviation: Loudoun County Department of Planning

Source_Contribution:

Loudoun County Department of Planning is the source for population, housing units, households, and employment for TAZs.

Process_Step:

Process_Description:

TAZ shapefile from the Metropolitan Washington Council of Governments was overlaid the 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 TAZs are designated to follow. Census blocks are designated to follow these types of features as well. Census block shapefiles were downloaded from the U.S. Census Bureau. Overlaid the Census Bureau block shapefile 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 block lines using Loudoun County Government's detailed GIS layers. TAZ boundaries that do not follow block boundaries were identified. The identified boundaries were digitized using Loudoun County Government's detailed GIS layers, and in doing so, census blocks were split into parts. Created the TAZ layer by assigning the TAZ number to each census block or census block split area and then spatially dissolving the census block with splits layer. The population, household, and housing unit totals were derived by summing U.S. Census Bureau 2010 Census block and census block split area totals. For split census blocks, the percentage of a blocks housing units that existed for the 2010 Census in the split area was determined using a combination of building permit, occupancy permit, and assessment data. This calculated percentage for a census block's split area was then multiplied by the population, household, and housing unit totals of the census block to derive the estimated population, household, and housing unit totals for the block split area.

Process_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County Department of Planning

Contact_Position: Demographer

Spatial_Data_Organization_Information:

Indirect_Spatial_Reference: Loudoun County

Direct_Spatial_Reference_Method: Vector

Point_and_Vector_Object_Information:

SDTS_Terms_Description:

SDTS_Point_and_Vector_Object_Type: GT-polygon composed of chains
Point_and_Vector_Object_Count: 282

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Planar:

Map_Projection:

Map_Projection_Name: Lambert Conformal Conic

Lambert_Conformal_Conic:

Standard_Parallel: 38.03333333333333
Standard_Parallel: 39.2
Longitude_of_Central_Meridian: -78.5
Latitude_of_Projection_Origin: 37.66666666666666
False_Easting: 11482916.66666666
False_Northing: 6561666.666666666

Planar_Coordinate_Information:

Planar_Coordinate_Encoding_Method: coordinate pair

Coordinate_Representation:

Abscissa_Resolution: 0.00041666666666666593
Ordinate_Resolution: 0.00041666666666666593

Planar_Distance_Units:

Geodetic_Model:

Horizontal_Datum_Name: D North American 1983 HARN
Ellipsoid_Name: GRS 1980
Semi-major_Axis: 6378137.0
Denominator_of_Flattening_Ratio: 298.257222101

Entity_and_Attribute_Information:

Detailed_Description:

Entity_Type:

Entity_Type_Label: GISDBB.GISBROW.TAZ_POLY

Attribute:

Attribute_Label: TA_HHLDS2010

Attribute_Definition:

2010 households of the TAZ. Households are occupied housing units.

Attribute_Definition_Source: Department of Planning