This data set contains photographic information obtained for the National Agricultural Imagery Program (NAIP) and is comprised of scanned photographs that were acquired with a precision aerial mapping camera at a nominal scale of 1:40,000 on color positive film. Acquisition was leaf on with mature crops prior to harvest. Twenty-five counties in Nebraska were finished. The subcontractor flew during five days in July and August, completing all image acquisition by mid August 2001. The aerial film was scanned and digitally rectified at a resolution of approximately two meters GSD for use as a visual interpretation tool and to take area measurements of farm fields to within +/- 5% accuracy. Horizontal accuracy of the imagery can be very good. However, the imagery was not intended to meet National Map Accuracy Standards. Significant horizontal offset relative to data of higher order accuracy can occur. This digital imagery serves as a base for Farm Service Center GIS applications and is used to administer USDA commodity support programs and conservation planning. NAIP imagery is quarter quadrangle centered to provide consistent and repeatable coverage. Imagery from NAIP can be ortho-rectified to meet or exceed national map accuracy standard, or reproduced as a photographic product in a variety of scales and sizes.
To compile and distribute digital or analog aerial photography of selected cropland areas in support of Farm Service Agency compliance and conservation programs.
ground condition
None, The Aerial Photography Field Office asks to be credited in derived products.
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Sample images for a county were displayed in ArcView against MrSID format mosaicked Digital Orthophoto Quadrangles (MDOQs) for that county. That contract imagery was checked to see how well it registered to the MDOQ as well as accurately adjacent individual images compared to each other in overlap areas. The county farm field boundary, Common Land Unit (CLU), boundaries were added to ArcView view to see how well the CLUs registered to the digital imagery as well. The registration checks allowed comparison of area measurements between the MDOQ and the digital imagery. The color film was inspected using APFO common standards for film.
The imagery and film provided by the contractor far-exceeded contract specifications. The imagery was orthorectified although the contract stipulated georectification only. The products were essentially cloud free and very easy to work with. Area measurements were within five percent of the same area measurements on the MDOQ. In addition, the contractor voluntarily resampled two counties to one-meter resolution, and this imagery could easily meet USGS standards for DOQs.
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The positional accuracy for the digital datais tested by visual comparison to a data source with a higher order of accuracy.
Digital Ortho-rectifed Image.
The 1:40,000 color aerial photography film was scanned to produce a nominal 2 meter GSD image. The scanned images were rectified using a variety of image processing packages. An operator interactively registered each scanned image to several photo-identifiable points on a compressed mosaic of digital ortho-photo quarter quadrangles supplied by the USDA. Software tools were then used to rubber sheet each scanned image to the compressed ortho mosaic. Each rectified image was then quality checked to ensure that the accuracy specification was met. The rectified image was output in geotiff format in a nominal 2 meter ground sample distance.
Metadata imported.
8-bit pixels represent brightness values 0 - 255
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In no event shall the creators, custodians, or distributors of this information be liable for any damages arising out of its use (or the inability to use it).
Color Positive
301 Centennial Mall South, P.O. Box 94676
http://www.dnr.ne.gov