The National Map

Important Note regarding the National Map Viewer

Because of ongoing changes to the National Map Viewer file formats we recommend using the Multi Resolution Land Characteristics Consortium MRLC page to download elevation and clutter data in the BIL format. You can also use the prepackaged grid float format described below.

The National map view page can be found at http://viewer.nationalmap.gov/viewer/ (Not recommended)

Information

The National Elevation Dataset (NED) is a new raster product assembled by the U.S. Geological Survey. NED is designed to provide National elevation data in a seamless form with a consistent datum, elevation unit, and projection. Data corrections were made in the NED assembly process to minimize artifacts, perform edge matching, and fill sliver areas of missing data. NED has a resolution of one arc-second (approximately 30 meters) for the conterminous United States, Hawaii, and Puerto Rico and a resolution of two arc-seconds for Alaska. More info can be found at http://gisdata.usgs.net/NED/.

Prepackaged Gridfloat 1" and 1/3" data download

http://cumulus.cr.usgs.gov/webappcontent/neddownloadtool/NEDDownloadTool.html

Enter the coordinates for the area to be downloaded or select a state and region. Be sure that the longitudes are negative for the west.

Be sure to click the download links for the "Pre-packaged Float format" at the desired resolution.

Extract all the files in to a common folder.

Using the Gridfloat data in Pathloss 5

Click Configure -> Setup GIS Configuration and configure the primary DEM

Select the top level folder that contains all the DEM. Close the index and click OK. (Save the GIS file.)

Using the seamless NED data with Pathloss 4

Decompress the dataset to its own directory. The dataset is comprised of 16 files…

*.aux          *.hdr       METADATA.dbf  Metadata.xml
*.bil          *.prj       METADATA.prj  NED DataDictionary.pdf
*.bil.aux.xml  *.stx       METADATA.shp  NED_Release_Notes_June10.pdf
*.blw          meta1.html  METADATA.shx  output_parameters.txt

In Version 4.0 make sure to use NED CONUS for data in Alaska. Do not use NED Alaska.

The NED (CONUS) data uses the NAD83. NAD27 Coordinates are transformed automatically.

The SRTM data uses the WGS84. NAD83 and NAD27 Coordinates are transformed automatically.

• In the Pathloss program click Configure – Terrain Database and depending on the dataset select either NED CONUSor NED Alaska from the drop down list.

• Click Setup Primary (or Setup Secondary depending on your selection).

• Click the file button and browse to find and load the file with the BIL extension. The program is now setup to use the selected BIL file.