USGS Topo GeoPDFs Available
10/11/2011 9:03 AM
PDF (Portable Document Format) digital files are now available for US Geological Survey topographic quadrangle maps. Each file is essentially a scan of a topographic map with the added feature of being georegistered. The files can be used as a PDF file, enabling users to view topo maps onscreen. The GeoPDFs give the user the ability to turn on and off layers shown on the map (e.g. hydrography, transportation, imagery, contour lines, etc.).
Searching on the keyword "geopdf" in the Geospatial Portal will show all the GeoPDFs in the search results (Please note: Not all topographic maps in NC have a corresponding GeoPDF yet, and therefore are not in the portal). To refine the search, users can search on the USGS topographic map name. If you do not know the topographic name you can search by geographic area. This process is explained below.
To search by geography, go to the Search tab and zoom to your area of interest on the map. Then, change the search criteria (just above the map) from "Anywhere" to either "Intersecting" or "Fully Within." Lastly, enter the keyword "geopdf" in the search box and click Search. Results will be shown to the right of the map. This process is illustrated below. In this example we are searching for all the GeoPDFs in and around the area of Boone, NC:
What is returned are the search results for all the GeoPDFs whose "footprints" (the red outlined boxes on the map) intersect the extent of the search map. If we had selected "Fully Within" rather than "Intersecting", then all the GeoPDF footprints that were wholly within the extent of the map would have been returned in the search results. To download the GeoPDF, click on the title of one of the search results, and then click Download. This link will take you to the NC OneMap FTP repository of the GeoPDFs, where you can save the desired file to your desktop.