Anton, and the rest:
APRS does much more than track transmitters. WX data can be added, or any other telemetry. The location doesn't have to be where the transmitter is, it can be anywhere.
Example: if you have a HAZMAT incident, you create an object at that location, so the incident shown on all the maps. If you also display the windspeed and direction reports from the WX stations nearby, it is easy to predict where the toxic cloud is going to blow, and start your evacuations there.
My homepage http://my.ohio.voyager.net/~avcook has links to all kinds of APRS information and software. Just click on the world.
Alan, N7CEU OOC Ohio Section ARRL
Together: TEAM ANGEL