The District of Columbia

Contours - 2 foot

Contours - 2 foot

by Office of the Chief Technology Officer on 12/02/2009

Keywords
About: Topography, breakline, contour, elevation
Taking place at: Washington, D.C., District of Columbia, DC, DC GIS, DCGIS

Abstract

2 foot contours. This dataset contains locations and attributes of 2-ft interval topography data, created as part of the DC Geographic Information System (DC GIS) for the D.C. Office of the Chief Technology Officer (OCTO) and participating D.C. government agencies.

In addition to the 2-ft contour data ancillary datasets containing an ESRI geodatabase of masspoints and breaklines. 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.

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 DC Office of the Chief Technology Officer (OCTO)

801 7th Street SW
Washington DC , 20024, USA

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

Credits

Office of the Chief Technology Officer

Data accuracy

Accuracy
Contours were coded as either intermediate or index depending on the elevation attached to each contour. The tiled contours are then processed along with additional data such as buildings so that indefinite or hidden contours can be properly coded.

Logical consistency
Validated by KCI Technologies, Inc. and OCTO. Contours were checked for overlaps or dangles. Any errors that may be flagged are corrected by a GIS technician. Tiles of data are also checked to ensure that contour ties between tiles are spatially connected and have like attributes. If any errors are found they are corrected by a GIS technician. Contours are checked for proper connectivity and topology by using various ESRI tools.

Completeness
Data believed to be complete and accurate, subject to change. Validated by responsible agency"

Horizontal positional accuracy
Horizontal Accuracy of planimetric/topographic data is in accordance with ASPRS Class I Accuracy standards.

Vertical positional accuracy
This data has been tested in accordance with the NSSDA Spatial Data Standards. Fifty-seven (57) checkpoints were used in the evaluation. Checkpoints were derived from multiple sources including: 1) KCI surveyed independent checkpoints, 2) Checkpoints/GCPs used for a previous mapping program (14th street bridge), 3) Survey control withheld from the final aerial triangulation solution All of these tests were based on a final Airborne GPS, AT, and DTM. As a result the data has been found to have a vertical RMSE of 1.0ft. At the 95% confidence level this is 2.0ft. This data has been found to meet ASPRS Class 1.5 Accuracy Standards. In comparison to National Map Accuracy Standards where 90% of the checkpoints should be within 1’ our findings indicate 86% of the well defined points are within 1’ and the remaining 93% are within 2’. Any accuracy limitations were primarily impacted by flying height, image resolution, and lack of sidelap in specific areas which impacts the overall block adjustment.

The contours are good for planning purposes but should not be used for precise engineering and survey work at the ASPRS class 1 accuracy standard level.

Lineage / Sources

  • Aerial Photography and AT solution
    aerial photography, attributes and location
    2008 DC aerial photography and AT solution
    by Office of the Chief Technology Officer, 20080528
Lineage / Processes

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 DC 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 - 5:30 pm

Entity

DCGIS.TopoLn

Attributes

  • Shape / ESRI
    Feature geometry
  • OBJECTID / ESRI
    Internal feature number.
  • GIS_ID
    OCTO GIS Internal Identifier
  • FEATURECODE
    Breakline Feature Code
  • DESCRIPTION
    Breakline Feature Code Description
  • ELEVATION
  • CAPTUREACTION
    Capture Action of Feature
  • SHAPE / ESRI
    Feature geometry.
  • CAPTUREYEAR
    Capture Date of Feature
  • SHAPE.LEN

Metadata

FGDC Content Standards for Digital Geospatial Metadata / FGDC-STD-001-1998 as of 12/28/2009

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 pm