Persistent sand polygons, Lower Missouri River

Shapefile created by USGS. This is a polygon created from Landsat TM imagery. All Landsat 4-5 TM images overlapping the Missouri River downstream from Gavins Point Dam were identified and examined for lack of clouds. Usable images were classified into sand, vegetation, and water. Classified images were then merged, and the number of times a given pixel was classified as either sand, vegetation, or water were computed. The presented dataset represents pixels which were classified as sand in greater than 5% of images which were collected during a growing season defined as julian day 116-296 (to preclude vegetated islands, which classify as sand outside of foliation), translated into polygons.