Texas and US 
Digital Ortho Quads (DOQ's)

Windrose Data Corporation offers high-resolution digital orthophotography for the States of Texas and Louisiana. This imagery utilizes the 1994 - 1998 National Aerial Photography Program (NAPP) color infrared (CIR) data products. NAPP photography is acquired at 20,000 feet above mean terrain with a 6-inch focal length lens. The flight lines are quarter quad-centered on the 1:24,000 USGS maps. NAPP photographs have an approximate scale of 1:40,000 and are flown in color infrared.

These digital images have been corrected to minimize the distortion related to the camera sensors and terrain. The result is a digital image with the characteristics of a photograph and the accuracy/geometric qualities of a map. This permits direct measurement of distances and areas. This makes digital imagery a geometrically accurate base map that can be overlaid and manipulated like any other GIS coverage or GIS layer.

Use of DOQs:

Digital Orthophoto Quadrangle (DOQ) data is used by the private sector, governmental entities, and educational institutions in many disciplines. As a GIS base data layer, DOQs may be used for many mapping projects such as:

DOQ COST and Availability:

DOQs are available upon request on CDROM. From the standard 1-meter data a variety of resampled data products are available, including 2.5-meter, 10-meter and 30-meter.

Request can be made via email, fax or phone. DOQs come standard on CDROM and cost only $45.00 per quad with discounts available for high volume orders.

DOQ Coverage:

The extent of available imagery is indicated in green on status map. Some areas of Texas do not have orthophotography completed to date. These aerial photographs were obtained in these areas in 1994-95.

Technical Specification:

Standard Resolution: 1-meter pixel 
Image Projection: UTM 
Datum: NAD83 
Ellipsoid: GRS80 
Image: Units Meters 
Color: Color Infrared

Data Type: 24-bit 
Scale: 1:12,000 
Image Coverage: 7.5' with 3.75' quarter quad 
File Format: GeoTiff 
File Size: Approx. 150 megabytes for 1 meter, 3.75' quarter quad