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The State of Delaware 1-meter resolution color-infrared digital ortho-photos are available for the entire state. Airphotos
were taken in March, 1992, digitized and georeferenced to Delaware State Plane coordinates (meters, North American Datum
1983, based on GRS 1980 spheroid). The source data are 140 MB 24-bit color files for each of the 172 quarter-quads in
Delaware. In these images the infrared reflectance (typically from vegetation) is displayed as red; red reflectance is
displayed as green; green reflectance is displayed as blue.
To facilitate dissemination of these data, the 172 DOQ's were resampled covering the state to UTM coordinates (meters, NAD 1983) at 5-meter resolution in 8-bit color, achieving initial file size reductions of almost 99 percent. While the original DOQ series requires approximately 25 gigabytes of storage, our series totals approximately 310 megabytes, and is storable on a single CD in .BIP (SPOT Image) format (see below). A nearest-neighbor (i.e. center-cell selection) resampling was used procecure which generates a high-contrast image with some blockiness in verysmall features. Each transformation used four 3.75-minute-interval reference points located near the corners of each image. Each resampled image is approximately 1210 x 1510 pixels, with a 10-pixel (50-meter) border cropped out to eliminate slight edge skewness resulting from the reprojection. Images still have at least 500 meters of edge overlap. Color palettes were brightened and adjusted for improved consistency using Adobe Photoshop. Sun glare has been masked out of water pixels in most coastal images in order to correct color palettes. |
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