Seamless Topographic Map Mosaics are great for planning hiking/bicycling trips, environmental research, land use planning, and many other uses. They also make a great base map for using Google Earth in off-line mode for those times when a high speed wireless connection is not available.
The maps are available in downloadable bundles and have been specially designed to work with Google Earth. Each map bundle typically contains 64 7.5-minute series (1:24,000 scale) USGS topographic maps and covers a 1×1 degree area of the United States (about 3,000 to 4,000 square miles). The maps have been merged together to create a seamless mosaic without the map borders and they are georeferenced to align with the underlying imagery in Google Earth.
In addition, the 10-meter National Elevation Dataset (NED) has been used to apply hill shading to the maps to enhance the topography. The hill shading also helps when using the maps in off-line mode since you won’t have access to the terrain elevation data normally provided by Google Earth. The maps have been created using Google Earth Super Overlays, which means the maps will automatically increase in resolution as you zoom in.
An installation program is included that will automatically add the maps to Google Earth on your PC (so long as Google Earth is already installed). Mac users should be able to install the maps using the unzip command in the Terminal application (“unzip N46W123-Setup.exe” for example). There is also a Mac program call The Unarchiver that might allow you to run the EXE file directly, but I do not have the ability to test it out. If anyone has any other Mac tips, please post a comment.
The map bundles range in size from 100 to 600 megabytes, and are priced at $5.00 per bundle, which works out to less than 10 cents per map. Some of the coastal areas are priced at $1.00 if there are only a few maps in the coverage area. You can purchase multiple map bundles and they will join together seamlessly in Google Earth.
Please visit the new GELIB Store to purchase the maps.
The free map for the month of December covers the Mt. St. Helens area of Washington and is 555 megabytes. Check back next month for a different free map. Please try before you buy as there are no refunds.
If you have any questions or problems, you can contact me here.
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