Data Management Plan

An orthoimage is remotely sensed image data in which displacement of features in the image caused by terrain relief and sensor orientation have been mathematically removed. Orthoimagery combines the image characteristics of a photograph with the geometric qualities of a map. For this dataset, the natural color orthoimages were produced at 0.3-meter pixel resolution (approximately 1-foot). The design accuracy is estimated not to exceed 6 meter horizontal RMSE for locations within the United States. Each orthoimage provides imagery for a 1500-meter by 1500-meter block on the ground. The projected coordinate system is UTM with a NAD83 datum, spheroid GRS80. There is no image overlap between adjacent files. The naming convention is based on the U.S. National Grid (USNG), taking the coordinates of the SW corner of the orthoimage.

Process Steps:

• 2009-01-05 00:00:00 - Ground control consisted of photo identifiable surveyed points within the United States. The imagery was collected at an average altitude of 9843 ft above mean terrain (AMT) using a frame-based Z/I Imaging Digital Mapping Camera (DMC). Overlap between adjacent frames along the flight line was approximately 60% and overlap between adjacent flight lines was approximately 30%. Corrections for camera and airplane exterior orientation (EO) variations were made with input from a combination of ground-, plane-, and space-based survey inputs (e.g., ABGPS, IMU, CORS Stations, Base Stations). The DMC collects 12-bit image data per channel which are resampled during post processing to standard 8-bit image data. The reduction in dynamic range (from 4,096 to 256) is performed in a manner designed to capture the greatest amount of information in each image, and preserve bright and dark values. Image quality was verified during the post flight review phase. Factors considered during this review included but were not limited to the presence of smoke and/or cloud cover, contrails, light conditions and sun glint. Pan-sharpened red, green, blue, and NIR bands were combined to generate digital image frames. Geometric correction of mosaicked frames of land areas within and laterally contiguous to the United States was performed via aerial triangulation and orthorectification using a recent DSM of the area provided as GFI (SRTM2, DTED2, Intermap NEXTmap USA, Canada NED, Mexican Border Lidar), and supplemented with higher resolution DSM data where readily available. The vertical accuracy of the DSM varies based on the elevation postings of GFI products and requirements thereof. Color balancing was performed to reduce radiometric variability between frames, and seamlines were generated using both automated and manual methods. Project specified tiles of the red, green, and blue bands were extracted from the mosaic to produce a natural color digital orthophoto image map. Final image tiles were reviewed for artifacts and anomalies and adjusted as part of quality control procedures. When necessary, local corrections to the imagery were performed to minimize such effects.