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[aprssig] APRS Destination and TARGET Waypoints

Robert Bruninga bruninga at usna.edu
Wed Dec 23 14:26:30 UTC 2009


APRS Authors:

All authors are reminded that APRS has had a
DESTINATION(waypoint) function since 2004 where mobiles can not
only transmit their present position, but can also occasionally
transmit their DESTINATION using a special destination waypoint
symbol.  This allows all APRS display systems to not only show
the mobile position, but his intended target destination.
Display systems are supposed to connect the mobile and the
destination with some kind of graphic (such as a line) to show
where he is going.  The symbol is "\/".  And should allow
overlays..

Please see http://aprs.org/APRS-docs/MOBILE.TXT

It is trivial to transmit one of these for your mobile:

1) Manually switch your position to your end point.
2) Manually switch your SYMBOL to "\/"
3) Transmit it a few times until you are sure it has been
received
4) Restore your normal Mobile symbol and return to GPS tracking

I do not know which if any other APRS applications besides
APRSdos implemented this, but one would hope that future mobile
systems can make this automatic and all display systems will
implement and display them.

If some of the big players implemented this feature then users
would be more aware of its potential and maybe use it more.  In
many cases, knowing where a mobile is headed is equally if not
more valuable than its present position.  

In APRSdos, a special line was maintained between the mobile and
his target. In a full graphical environment, I would vote for a
fat transparent hazy blob connecting the two, since we do not
know his specific route, but we do know where he is going...
And a fat blob would cover most of the possible route.

Bob, Wb4APR





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