APRS
What is APRS?
APRS (Automatic Position Reporting System) is a packet radio system for displaying and sharing information using map displays. Information that can be plotted includes fixed and mobile amateur station position reports; telemetry from balloons, aircraft, automated weather stations; DX spots and so on. All it takes to run APRS is a PC-compatible computer running DOS, Windows, MacOS, or Linux or a Palm Pilot, a 2 meter transceiver and a 1200 baud Terminal Node Controller (TNC), TinyTracker, Mic-Encoder, Kenwood TH-D7, TM-D700, TM-D710, Yaesu VX-6R, etc.
Applications of APRS include vehicle tracking during public service events, use in the National Weather Service SKYWARN program, and just chatting with others (via keyboard).
To learn more about APRS, start at: http://aprs.org
Where to get APRS
You can find most APRS versions at the TAPR ftp site, ftp://ftp.tapr.org/aprssig.
Most of currently available version of APRS software are shareware programs that you can use for free but that encourage you to register (pay the shareware fee to the authors). Unregistered versions nag you each time you start them to register, primarily by preventing you from saving your configuration. This means you have to reenter your callsign and two or three other pieces of information each time you start the program. This is called Nagware.
Note that the various APRS versions are written by different people so if you are considering one or the other for your PC, you should try them both for a while first and decide which you want to spend your money on (or spend no money and use Xastir:-).
Featured APRS app: Xastir
If you are into Linux (or want to run Cygwin under Windows), check out Xastir. Xastir is totally free (GPL) software and is perhaps the most sophisticated version, supporting a variety of local on-disk and Internet map sources and other features, including:
ESRI shape file vector mpas including those based on US Census Tiger/Line, NOAA, and others.
Geotiff raster maps, including USGS DRGs (24 and 100K).
Internet maps generated on the fly by the tiger.census.gov map server, Terraserver satellite images, etc.
Speech announcements of the position of a tracked station and proximity alerts.
Sophisticated weather handling including automatic highlighting of NWS warning areas.
Tools to convert GPS tracks into shape file maps.
and lots more.
You can find pre-packaged Xastir and pre-req software here for Red Hat Linux. But if the files look a little out of date, please check the official Xastir site for updates.
Westchester County Maps
If you are using APRS for DOS or Windows, download the following files and UNZIP them in your main APRS directory.
A collection of shapefile maps for Xastir is currently a work in progress. Contact me if you are interested. I hope to have them packaged Real Soon Now and am working on using maps from Westchester County GIS.
NOTE: You will need 15M of free disk space for the DOS maps
nywcmap1.zip - DOS maps, file 1 of 2.
nywcmap2.zip - DOS maps, file 2 of 2.
nywcwin1.zip - Mac/Win maps, file 1 of 1.
xmd1.zip - March of Dimes WalkAmerica (use "XMD" maplist).
xms1.zip - Multiple Sclerosis Society MS Walk (use "XMS" maplist).
 - American Diabetes Association Tour de Cure (June 8th).
APRS digipeaters covering Westchester and vicinity
In early 2004, the old APRS digipeater that had been in service since December, 1998, was replaced. The new digipeater, which provides advanced APRS functionality, consists of a PC running Linux and the aprsdigi software APRS digipeater. The PC has two sound cards and uses HB9JNX/AE4HWA's DSP sound modem software to decode and encode packet. One sound card is connected to a transceiver on 144.39, the national APRS frequency. The other is listening to the result of the 147.06 repeater's input voter (which selects the best signal among the several remote receivers). This allows the same system to act both as a standard APRS digipeater and as a voice gateway, allowing "Mic encoded" packet to take advantage of the superior coverage of the voice repeater system.
Several additional local APRS digipeaters running aprsdigi have been added since then: W2AEE-1 covering the Northwest corner of the County; WB2ZII-14 near Peekskill and WB2ZII-15 near Yorktown Heights.
APRS automatic vehicle location and telemetry is used in many parts of the country for tracking resources during public service events and emergency responses. The WECA MIC-E gateway couples the excellent coverage of the WB2ZII 2 meter voice repeater system with the mapping capabilities of the several APRS programs now available for DOS, Mac, Windows, Linux, and Palm. In addition to personally-owned APRS trackers, WECA has packaged several Kenwood TM-D700 trackers that are used for a variety of public service events. These have callsigns like WB2ZII-1, WB2ZII-2 through WB2ZII-5 or so.
APRS on the Internet
The Internet is used to interconnect APRS radio systems and to provide a global place to find APRS stations via the web. If you search for WB2ZII you will find the WECA voice/APRS repeater system. Follow the link for nearby stations and you'll see who's around Westchester right now.
A first: the MS Walk on 4/20/97
See this page for a javAPRS replay of the Multiple Sclerosis walkathon at Rye Playland. This is our first public service event test of APRS.
How the DOS maps were made
These maps were generated by Alan Crosswell, N2YGK using US Census TIGER/Line 1995 data and a program I wrote called tig2aprs which runs under the Linux operating system. To see more about this program, take a look at my APRS web page, http://www.cloud9.net/~alan/ham/aprs.
These maps have been made obsolete by Xastir and UIView's mapping capabilities.