The District of Columbia

IMAGE.Ortho1999

IMAGE.Ortho1999

by DC GIS

Keywords
About: Imagery, Aerial Photography, Planning, imageryBaseMapsEarthCover
Taking place at: Washington, D.C., District of Columbia, DC, DC GIS, DCGIS

Abstract

1999 Orthophoto Mosaic, acquired 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. 20cm resolution.

DC-OCTO-GIS acquired the true color digital orthoimages through the planimetric mapping effort. A mosaic was generated and compressed into MrSID format for easier display and planning purposes.

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

Data cannot be redistributed in any manner without written authorization. OCTO 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 pm

Credits

DC Office of the Chief Technology Officer (OCTO)

Data accuracy

Accuracy
N/A

Logical consistency
Data believed to be complete and accurate as of the time period cited. Subject to change. In process of validation by source and/or responsible agency.

Completeness
Data believed to be complete and accurate, except for areas of DC deemed sensitive for national security purposes. Validated by source and/or responsible agency.

Horizontal positional accuracy
Validated by source and/or responsible agency. The horizontal accuracy is guaranteed to meet National Map Accuracy standards which calls for 90% of well defined points to fall within .85 meters of true position. This accuracy was verified by the completion of a fully analytical aerotriangulation adustment which resulted in an RMSE of 1 part in 10,000 which is recognized as necessary to achieve the accuracy requirement.

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

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



fax: (202) 727-5660
hours: 8:30 am - 5 pm
As part of the planimetric data conversion effort, OCTO-GIS acquired orthophotography to compliment the digital data. Originally, the orthophotos were delivered as tiled TIFF images, using the WGIS delivery tiling scheme. However, to serve the needs of a broader user community, OCTO-GIS directed the contractor to generate an orthophoto mosaic. This mosaic was compressed into MrSID format for ease of use. The image contains 20cm pixels.

EDMD acquired new aerial photography of the District of Columbia in the spring of 1999 prior to the emergence of deciduous foliage. Aerial photography was exposed at an altitude of 7,200' AMT using a Wild RC-20 or RC-30 camera system that is equipped with forward motion compensation and a 12" (300mm) focal length lens cone 600'. The flight design developed in 1995 was duplicated. The design calls for an approximate total of 1,000 frames in 24 North-South oriented flight lines. Forward overlap between frames within each flight line was 80%. Sidelap between adjacent flight lines was 48%. Aerial photography was captured in natural color using Kodak Aerocolor negative film type 2445. Aerial photography was not exposed using airborne GPS due to the existence of an existing control network created in 1995.

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
OCTO 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. Subject to terms and conditions of the Memorandum of Agreement. Memorandum of Agreement must have authorized signature.

Distributed 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

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Metadata

FGDC Content Standards for Digital Geospatial Metadata / FGDC-STD-001-1998 as of 12/14/2007

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 pm