The District of Columbia

Census Tracts - 1940 - DC (Tract40Ply)

Census Tracts - 1940 - DC (Tract40Ply)

by Office of the Chief Technology Officer on 06/12/2002

Keywords
About: society, Census Tracts, Tracts, boundaries, Government Jurisdictions, Census
Taking place at: Washington, D.C., District of Columbia, DC, DC GIS, DCGIS

Abstract

Census Year 1940 Census Tracts. The dataset contains polygons representing CY 1940 census tracts, created as part of the D.C. Geographic Information System (DC GIS) for the D.C. Office of the Chief Technology Officer (OCTO) and participating D.C. government agencies. Census tracts were identified from maps provided by the U.S. Census Bureau and the D.C. Office of Planning. The tract polygons were created by selecting street arcs from the WGIS planimetric street centerlines. Where necessary, polygons were also heads-up digitized from 1995/1999 orthophotographs.

All DC GIS data is stored and exported in Maryland State Plane coordinates NAD 83 meters.

METADATA CONTENT IS IN PROCESS OF VALIDATION AND SUBJECT TO CHANGE.

Purpose

This data is used for the planning and management of Washington, D.C. by local government agencies.

Access constraints

Contact OCTO GIS. Any data obtained outside of OCTO GIS are unauthorized copies.

Use constraints

Acknowledgment of the DC Geographic Information Systems Program (DC GIS). The District of Columbia Government makes no claims as to the completeness, accuracy or content of any data contained hereon, and makes no representation of any kind, including, but not limited to, the warranty of the accuracy or fitness for a particular use, nor are any such warranties to be implied or inferred with respect to the information or data furnished herein.

Point of contact

GIS Data Coordinator
in D.C. Office of the Chief Technology Officer

441 4th St NW, Suite 930 South
Washington DC, 20001, USA

fax: (202) 727-5660
hours: 8:30 am - 5:00 pm

Credits

U.S. Census Bureau
D.C. Office of Planning

Data accuracy

Accuracy
Data believed to be complete and accurate as of the time period cited. Subject to change. Digital version compared with original source data for accuracy and completeness. In process of validation by source and/or responsible agency.

Logical consistency
In process of validation by source and/or responsible agency.

Completeness
Data believed to be complete and accurate, subject to change. Digital version compared with original source data for accuracy and completeness. In process of validation by source and/or responsible agency.

Horizontal positional accuracy
In process of validation by source and/or responsible agency.

Vertical positional accuracy
N/A

Lineage / Sources

  • District of Columbia by Census Tracts 1940
    paper, boundaries and attributes
    1940 Census Tracts
    by N/A, 1940
Lineage / Processes
GIS Data Coordinator
in D.C. Office of the Chief Technology Officer

441 4th St NW, Suite 930 South
Washington DC, 20001, USA

fax: (202) 727-5660
hours: 8:30 am - 5:00 pm
1940 Census tracts were identified from public records (U.S. Census Bureau and D.C. Office of Planning) and initially created by selecting street arcs from the WGIS planimetric street centerlines. Where necessary, tracts were also heads-up digitized from 1995 orthophotographs. The digitized arcs and polygons were converted to shapefiles. The census tract datasets were selected using the shapefile from the snapbase coverage, creating coincident geography with the other DC GIS datasets. Digitized lines lacking a corresponding planimetric feature were retained. Snapbase arc attributes were populated with appropriate census designations. These planimetric features were built as lines and converted to polygons. Census coverages from each census year were built together since they share topology.

Planimetrics were created at a scale of 1:1,000. This means that a well defined feature falls within two feet of true position. When imported into the DC GIS geodatabase, the coverages shift 0.01mm since the geodatabase supports only 11 digits of precision, not double precision (16 digits). Line coverages, containing the polygon bounding attributes, accompany all polygons and are made available for editing and updating purposes. Census tracts are the only line coverages used to build polygons which carry attributes. Attribute data, kept in separate tables, was provided by US Census Bureau and the DC Office of Planning. In this case, street names were maintained at the request of the Office of Planning for ease of labeling.

All DC GIS data is stored and exported in Maryland State Plane coordinates NAD 83 meters.

Distribution

Most DC GIS datasets can be downloaded from "http://dcgis.dc.gov" on the data center page. Orders can also be made by contacting OCTO GIS at "dcgis@dc.gov", especially for datasets not available for download.

Distribution liability
Acknowledgment of the DC Geographic Information Systems Program (DC GIS). The District of Columbia Government makes no claims as to the completeness, accuracy or content of any data contained hereon, and makes no representation of any kind, including, but not limited to, the warranty of the accuracy or fitness for a particular use, nor are any such warranties to be implied or inferred with respect to the information or data furnished herein.

Distributed by
GIS Data Coordinator
in D.C. Office of the Chief Technology Officer

441 4th St NW
Washington DC, 20001, USA

fax: (202) 727-5660
hours: 8:30 am - 5:00 pm

Entity

DCGIS.Tract40Ply

Attributes

  • Shape / ESRI
    Feature geometry.
  • OBJECTID
    unique id
  • PERIMETER
    perimeter
  • TRACTS40_
    Coverage artifact
  • TRACTS40_I
    Coverage artifact
  • NAME
    Feature geometry.
  • WEB_URL
    web link url
  • SDE_TRACT40PLY_AREA
  • GIS_ID
    OCTO GIS sequential identifier
  • TRACTNO
    Census tract number
  • SHAPE / ESRI
    Feature geometry.
  • SHAPE.AREA
  • SHAPE.LEN

Metadata

FGDC Content Standards for Digital Geospatial Metadata / FGDC-STD-001-1998 as of 08/06/2007

Provided by
GIS Data Coordinator
in D.C. Office of the Chief Technology Officer

441 4th St NW, Suite 930 South
Washington DC, 20001, USA

fax: (202) 727-5660
hours: 8:30 am - 5:00 pm