Choctaw Geo Imaging (CGI) now offers a seamless mosaic of USGS Digital Ortho Quarter Quad (DOQQ) aerial photography. The new product, titled “geoORTHO,” is the latest addition to CGI’s geoSPATIAL product line. The line also includes geoTOPO, seamless topographic maps for the United States. The geoORTHO dataset contains several enhancements over traditional DOQQs, including radiometric balancing, mosaicking, database formatting, and colour standardization. CGI is introducing geoORTHO with special discounted pricing now through August 31, 2002. CGI’s geoORTHO is derived from the current USGS library of aerial photography. The imagery is ortho-rectified to a pixel resolution of one-meter, and meets national map accuracy standards at 1:24,000 map scale. The data is packaged by the state, geoORTHO STATE, and as a nationwide dataset, geoORTHO USA. Through CGI’s own production centre, the aerial data is enhanced through the following processes:
Radiometric Balancing – Using well-established software capabilities that were designed for high volume image production, the technique corrects for brightness or darkness, image vingetting and bi-directional radiometric issues. It creates a product that is aesthetically pleasing.
Black & White Conversion – The original DOQQ library is mixed between colour, colour infrared and black & white photos. CGI has converted the colour and colour infrared to create a consistent black and white dataset across the country. The conversion utilized all three bands of original image data, which creates a richer and more dynamic visual image compared to the traditional one-band process.
Mosaicking – This process eliminates the overlap and redundancy between the images. This process involves running a predefined mosaic line through each image, which identifies unnecessary overlaps. Finally, CGI’s feathering technique is designed to remove break lines between the images caused by radiometric differences in the original imagery.
Product Delivery – CGI stores its processed DOQQ data in a format that allows for easy access to any location in the database and the easy extraction of data in any common data format, compression routine, datum and projection. The product can be delivered in formats that work with common software such as ArcIMS, GeoMedia, MapInfo and others.