WA8LMF Home Page | Main Ham Radio Page | Main APRS Page | Updated  15 Dec 2007

Using US National Weather Service Shapefiles With APRS

Win/MacAPRS, APRSplus and UIview can highlight areas under a US National Weather Service watch or warning for counties and zones without using an individual map for each area. This is done by overlaying colored outlines on existing APRS maps. These outlines, known as "shapefiles", are in the native format of the ESRI Arcview professional GIS program widely used by government agencies and civil engineers.  These shapefiles are also directly readable by the four APRS programs mentioned above, as well as many other mapping, CAD and vector-draw applications.

The data required to light up these filled outlines on APRS maps is transmitted continuously by a special server maintained by Dale Huguley, KG5QD. It intercepts NWS messages, and reformats them into APRS-compatible format. The messages are inserted into the APRS Internet system by a "virtual igate" called "WXSVR". Details on these messages and their format is located here:

        http://www.aprs-is.net/Wx/ .

These NWS bulletins are received over a normal APRS Internet server connection. Bulletins for the entire country will be received even on regional-filtered APRS feeds.   Normally these bulletins are not transmitted over APRS RF. (You must have an Internet connection to receive them.)  These bulletins are ignored by normal APRS software but will be processed and displayed by the appropriate NWS options or software plug-ins. (For example, activating "UI-NWS" within UI-view.)

If you use the port 14580 user-defined filter port on an APRS server, adding  "t/n" to the normal port 14580 filter expression will cause the NWS bulletins to be sent, along with some weather-related APRS area objects originated by APRS users.  Again, you will receive all of the NWS bulletins for the entire country, even if you are filtering normal APRS position reports to a limited area.

Three sets of files for county outlines, standard NWS warning areas, and coastal marine zones are required.  The county outlines are fairly stable but the warning zones change frequently ( one or two times a year ) These files are downloaded from the NOAA/NWS website.
 

As of the time of writing of this page, the specific files needed are located at:
 

• Counties (filename always begins with "c_"):
     http://www.weather.gov/geodata/catalog/county/html/county.htm
  
   
• NWS Warning Zones (filename always begins with "z_"):
      http://www.weather.gov/geodata/catalog/wsom/html/pubzone.htm
  
   
• Marine Zones:(filename always begins with "mz_")
      http://www.weather.gov/geodata/catalog/wsom/html/marinezones.htm
      (You want the file  "Coastal Marine Zones Including the Great Lakes" on this page.)
   

These files need to be downloaded and unzipped into the appropriate folder for the program in question.  

• In APRSplus, this is the folder  \nws  located under the main APRSplus folder. Note that you have to pull down "Setup, Settings", expand the branch "NWS" by clicking on the plus sign, and then enter the exact filename of the three files. (The filename always begins with the same letter but embeds the release date of the current version. When updated versions of the files are installed, these entries have to edited to match.)
   
• In UIview, this is the path  \NWS\Shapefiles located under the main UIview folder.  Note that in the case of UIview, this is only the default location.  The entry  NWS_SHAPE_FILES_PATH=  in the UIview32.ini file can be edited to point to any folder on the system. This way, one copy of the shapefiles, which occupy about 40 megabytes of disk space, can be shared with two or more programs. (Place the shape files in the designated folder for the other program, and then let UIview "freeload" on them.)
  
  In UIView, the collection of data and display of the shape files is started by launching a separate application provided with UIview32.   Pull down "File" from the UIview menu bar and select "UI-NWS".
   
• In WinAPRS or MacAPRS, this is the folder \nwsshape located under the main WinAPRS/MacAPRS folder.