A data tip from NGS – Not exactly free, however, this is a fine resource for viewing and purchasing data and imagery… National Geographic DataDoors portal (www.natgeodatadoors.com)
Using DataDoors customers can select the exact area of coverage they want and order National Geographic’s TOPO! maps and i-cubed’s USA Nationwide Prime Imagery on CD-ROM or removable hard drives, or as a download. National Geographic Maps has scanned over 58,000 United States Geological Survey (USGS) quadrangles, color corrected them to create a consistent look and created a seamless map that spans all 50 U.S. states. The TOPO! map data is available at 1:24,000 scale in the continental United States and Hawaii, 1:63,360 scale in Alaska, and 1:100,000 scale in the continental United States. Digital Elevation Model (DEM) data is also available to help visualize vertical terrain and conduct spatial analysis and modeling. DataDoors delivers TOPO! maps and i-cubed imagery in many open formats, including TIF, JPEG, SID and ECW, and supports the selection of projection and data.
“We’re now able to deliver National Geographic TOPO! data to the professional GIS and non-GIS user communities within a self-serve, easy-to-use and economical Web portal,” said David Wright, director of professional products for National Geographic Maps. “Users can select their defined area of interest and quickly get the maps and imagery they need in the format they want. This application can generate massive single-image rasters, or user-defined tile structures to create raster catalogs, or even cached tile services for use in ESRI’s ArcGIS Server.”
The USA Nationwide Prime Collection provides 1-meter resolution or better and is color-balanced and optimized for continuous coverage. Offering National Geographic TOPO! maps with the USA Nationwide Prime Collection library provides a one-stop resource for high-quality topographic and aerial imagery for analysis, research and reports for land planners, developers, land management agencies, surveyors, utilities and energy firms, homeland defense, emergency response teams, firefighters, realtors and environmental firms.
See www.natgeodatadoors.com