miso@sushi.com wrote:

So there are fixed APRS sites. Are those packet facilities? I used the
google earth link.

Is N847X an airplane?
http://aprs.fi/info/N847X

Yup. Looks like he flew from Reno/Stead to Fallon.

APRS is packet but it's unconnected packet, unlike the
connected "packet BBS/mail" stuff that not too many
people do any more. Radio and TNC with or without
computer attached. Each station broadcasts position
data packets. Other stations digipeat the data
a prescribed number of times (not just blindly forever).
Once the signal takes a hop or two around the system it
typically reaches someone's APRS station that is
gated to the internet. So you and me in the Western
US can view the status of someone's low power
transmitter attached to their pet iguana in France
or their canoe in Belize.

You can also transmit telemetry data. Typically that
might mean weather info. But it could also mean current
on/off or analog state of anything, current battery voltage,
panic switch, freeze warn, trip wire, car hijack,
intruder alert etc. In the case of a vehicle status
situation, you could transmit ARRIVED/ENROUTE/FINISHED etc.
Same as police/fire/EMS etc.

With a computer or dumb terminal attached you can
send text messages/email to other stations or to
the internet based conventional email system.

There are HTs with all of that built in. Transmit
any of that data/info from the hand held.

Here's my van -
http://aprs.fi/?call=N0EQ-15&mt=p&z=15&timerange=3600

It's using an old 2m mobile radio, an old Tripmate GPS
and a TNC. It outputs position data every 2min. Takes
up the space of roughly two mobile radios. It's hands
off, no user interface needed. Lives under the seat
of my van.

If the green line TRACK is showing on my van map,
you can click on the red "bread crumb" points. Those
represent each 2 minute position report. Mine is set
to alternate outputting two kinds of GPS sentences.
One is position/bearing/speed, the other is position/elevation.
Clicking on the red bread crumb points shows you that info.

With vehicle based trackers, it's similar to the
position reporting systems that public service
or other fleet vehicle systems use. Add a laptop
PC to my system above and I have the equivalent of
an MDT, connected to thousands of other hams around
the world.

I've built small "trackers" into boxes about the size
of a guitar FX stomp pedal. GPS board, 350mw transmitter
and tiny TNC board the size of two postage stamps. Smaller
than a GLR road sensor.

These web page URLs that I post, like the aprs.fi stuff
are what some guys have interfaced to display the stations
on googlemaps or similar. You can also view/interact with
the network with an APRS software on a PC/Mac/Linux whatever
on your computer/blackberry/cellphone whatever. When you
view/interact using one of the software programs you have
all the options you might expect in various map views,
filter stations by distance/type/time (all mobile stations
within 100 miles, all weather stations in a 100km radius
of position xxn xxxw etc.).

Imagine, for example, something like GoogleEarth, add the
ability to view any number of ham stations; stationary,
mobile, airborne, boats, equistrian, hikers, bikes etc.
A lot of groups use APRS to track things like marathons, parades,
10k's, bike races. "Chase" vehicles or bicycles with an APRS
tracker show current positions of various runners or other
participants. Command post back at the start/finish
has a graphical view of what's happening.

The satellite guys typically plot the current position of
their birds into the APRS network. In that case, there's
not an APRS tracker on the bird, but they feed the
current status and position from whatever software
they use into the system. Displays a little satellite
icon on the map along with the usual satellite telemetry,
whatever that might be (I'm not a satellite guy).

Attach a small tracker box to your cow, tractor, backpack,
hot air balloon, package in transit, teenagers car etc.
Know where it's at all the time, plus maybe temp/voltage/
anything analog or digital as transmitted data.


Craig 'Lumpy' Lemke

www.n0eq.com