The Arizona State Cartographers Office (SCO) in cooperation with project partners, is making available a set of statewide USGS Digital Orthophoto Quarter Quads (DOQQs).
A DOQ is a digital image of an aerial photograph in which image displacement and distortion, caused by terrain relief and camera tilt, has been removed. Because a DOQ is a spatially accurate image with planimetric features represented in their true geographic positions, it combines the image characteristics of a photograph with the geometric qualities of a map. This DOQ imagery can be integrated into a Geographic Information System (GIS) and function as a cartographic base for displaying, generating, and modifying associated digital planimetric data.
The Arizona DOQ Project will produce a statewide, seamless data set of 1-degree blocks of color-balanced and edge-matched gray-scale 1:12000 DOQ imagery. The DOQQs will use the UTM projection on both the North American Datum of 1927 (NAD 27) and the North American Datum of 1983 (NAD 83). In addition, a complete set of the same DOQ imagery will be provided in a 20:1 compressed format as .ECW files using ER Mapper® compression software. Since a standard CD-ROM will hold a 1/2-degree block of DOQ data at this compression ratio, these DOQ data are easily transported into the field for use in wildfire management and other purposes. To maximize ease-of-use, all data sets will be available on two media; CDs (for smaller areas or use in the field) and Digital Linear Tape (DLT) format (for easier download of large areas to an agency server).
The accuracy and detail provided by the DOQ will allow participating agencies to:
- Evaluate their data for spatial accuracy and completeness.
- Make real-time modifications to their data.
- Create new data layers by digitizing visible features.
- Create second generation orthoimagery by registering new aerials to the DOQQs
The DOQ imagery can also be used as a backdrop for vector data or aid in migrating existing GIS layers from NAD27 to NAD83. If state agencies utilize DOQQs to accurately register their data then an enterprise GIS becomes more achievable since data from different agencies would more accurately overlay each other. Applications DOQQs may benefit include routing and emergency evacuation planning, facility management, wildfire management, environmental impact assessments, flood analysis, soil erosion assessment, and ground water and watershed analysis.