Summary

Description

This map layer is an Arc/INFO grid map of North America, excluding Hawaii and including the Caribbean and most of Mexico, that portrays at 1 sq. km resolution an index of land cover diversity calculated at 729 sq. km. scale. The map layer was created by applying a spatial filter to a published map of seasonal land cover regions (Loveland et al. 1991) known as NASLCR1_2L which was obtained from the USGS EROS Data Center Distributed Active Archive Center (DAAC). The spatial filter computed Simpson's (1949) index of land cover diversity within 729 sq. km. (27 x 27 pixels) windows from the proportions of different land cover types within a window. The [0,1] continuous index was discretized, and a byte representation (range: [1,245], with zero reserved for missing values) of the index value was stored at the center location in each window. The resulting surface map was projected to a standard projection, and clipped to shorelines defined by the STATP075 shoreline map (USGS). The data available through the National Atlas of the United States are in GeoTIFF format. This is a revised version of the May 2002 map layer, with a corrected shoreline for Greenland.