NLCD 1992, NLCD 2001, NLCD 2006, and NLCD 2011 are National Land Cover Database classification schemes based primarily on Landsat data along with ancillary data sources, such as topography, census and agricultural statistics, soil characteristics, wetlands, and other land cover maps. NLCD 1992 is a 21-class land cover classification scheme that has been applied consistently across the conterminous U.S. at a spatial resolution of 30 meters. NLCD 2001 is a 16-class land cover classification scheme that also has been applied to the conterminous U.S. at a spatial resolution of 30 meters, and includes Alaska, Hawaii, and Puerto Rico. NLCD 2006 quantifies land cover change for the conterminous U.S. between the years 2001 to 2006. Generation of NLCD 2006 helped identify and correct issues in the NLCD 2001 land cover and impervious surface products only, and no changes were made to the NLCD 2001 canopy product. For additional information, go to http://www.mrlc.gov/. See http://viewer.nationalmap.gov/help for assistance with The National Map viewer, services, or metadata.

The USGS US Topo Availability service from The National Map consists of footprints where US Topo products are currently available. Various green tints are used to reflect the year in which US Topo map products have been published. The service is updated daily and contains the same data used in footprints in the Map Locator & Downloader application program interface used in the USGS Store (http://store.usgs.gov). In addition to access through The National Map download client (http://viewer.nationalmap.gov/basic), US Topo products and other USGS publications are available through the USGS Store. For additional information, go to http://nationalmap.gov/ustopo.

<DIV STYLE="text-align:Left;"><DIV><P><SPAN>The USGS Imagery Only Large service from The National Map (TNM) consists of National Agriculture Imagery Program (NAIP) and high resolution orthoimagery (HRO) that combine the visual attributes of an aerial photograph with the spatial accuracy and reliability of a map. Digital orthoimage resolution may vary from 6 inches to 1 meter. In the former resolution, every pixel in an orthoimage covers a six inch square of the earth’s surface, while in the latter resolution, one meter square is represented by each pixel. Many states contribute orthoimagery to The National Map, and the USGS also relies on a partnership with the U.S. Department of Agriculture's Farm Service Agency. The National Map viewer allows free downloads of public domain, 1-meter resolution orthoimagery in JPEG 2000 (jp2) format for the conterminous United States, with many urban areas and other locations at 1-foot (or better) resolution also in JPEG 2000 (jp2) format. For additional information on imagery products, go to https://lta.cr.usgs.gov/node/300 and https://lta.cr.usgs.gov/high_res_ortho/.</SPAN></P></DIV></DIV>