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Michigan DOQQs 1 meter pixel resolution compressed in MrSid format.
Flown 1992-94

MrSID GeoViewer from LizardTech -- The MrSID GeoViewer is a stand-alone application designed to optimize the viewing of imagery that is in the MrSID imaging language. The new MrSID GeoViewer 2.1 includes the most popular features that have been requested by customers. The MrSID GeoViewer is available for Windows 95/98/NT.

MrSid Image viewers are available for free download from http://www.lizardtech.com/cgi-bin/products/products.pl

All DOQ's are referenced to the North American Datum of 1983 (NAD 83) and cast on the Universal Transverse Mercator (UTM) projection. Primary (NAD 83) and secondary (NAD 27) datum coordinates for the upper left pixel are included in the header so that users can spatially reference other digital data to the DOQ.

The accuracy and quality of USGS DOQ�s must meet National Map Accuracy Standards at 1:12,000 scale for 3.75-minute quarter quadrangles and at 1:24,000 scale for 7.5-minute quadrangles. Accuracy and quality depend on the following:

photographs that meet National Aerial Photography Program standards, which are quarter-quadrangle centered. The photographs are exposed at a flying height of 20,000 feet above mean terrain;
a DEM with the same area coverage as the DOQ and that is equal to or better than a level 1 USGS DEM having a root-mean-square error in elevation no greater than 7 meters;
a highly accurate image-scanning process that uses a scanning aperture between 7.5 and 32 micrometers (�m). A 1:40,000-scale image scanned with a 25�m aperture produces a ground sample distance of approximately 1 meter;
and identifiable ground control positions with coordinates acquired from ground surveys or aerotriangulation.

Uses for Digital Orthophoto Quadrangles

A DOQ can be incorporated into any geographic information system (GIS) that can manipulate raster images. It can function as a cartographic base for displaying, generating, and modifying associated digital planimetric data. Other applications include vegetation and timber management, routing and habitat analysis, environmental impact assess-ments, emergency evacuation planning, flood analysis, soil erosion assessment, facility management, and ground-water and watershed analysis. The accuracy and extraordinary detail provided by the DOQ allow users to evaluate their data for accuracy and completeness, make real-time modifications to their data, and even generate new files.

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