Thursday, September 9, 2010

Vicinity Tracking

Any TNC or tracker that transmits a periodic beacon can be tracked all across the
country without a GPS. But only to the nearest town or city or so. This is because you can use the "vicinity" tracking feature of APRS to see what was the Digipeater that the device first used most recently.

This is very powerful, because without the GPS, a few AA batteries and a low power tracker can operate for a year or more by sleeping in low power mode for 9.99 minutes out of every 10 and then only waking up to send out a packet (not a position packet, but a Status or other APRS packet) once every 10 minutes.

You can either check their position manually by looking at the packet and the PATH used or FIND.COM has a special CGI "&vicinity" that will plot a map of the last digi that heard it.

Hopefully all of the other APRS sites such as APRS.FI and have it as well.

This Vicinity tracking was fundamental to the original APRS as a means of identifying somewhere on the planet the source of a packet that entered the APRS system. With a global system like APRS, it is nice to be able to locate any packet (even without a position report) to a given digipeater footprint...

Bob, Wb4APR

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