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[aprssig] APRS Leaders and Dead Reckoning on APRS.FI

Bob Bruninga bruninga at usna.edu
Fri May 25 00:15:02 UTC 2012


Hessu reports about APRS.FI doing DR.  

> The DR line gives a good combination of added course indication 
> (in addition to the rotated symbol) *and* a speed indication 
> (if you watch it for a couple seconds you'll see it updating).
> For the end user, the good thing about the DR line is that 
> the speed indication is already in the correct scale, according 
> to the zoom level and the age of the last report.  
> You get a feel if it's changing quickly or slowly.

Wow, I never noticed it before.  I guess because you have to have a station
selected to see it.  I am usually looking at the big picture and see all
these mobile symbols (with no idea their age other than the [show last XXX]
history selection box.   I guess it would be too data intensive to expect
all moving mobiles to show it.  But maybe only those less than 10 minutes
old?

I wonder how long it DR's until it gives up waiting for a new posit and just
goes back to the misleading non-DR indication?

If I have my [show-last 1 hour] selscted, I wonder if it would be possible
to use track-history colors to show age?  Then all the histories that are
more than say 10 miuntes old could be GRAY and only those 1 minute or less
old could be RED, those 2 minutes or so orange, those 3 minutes old as
yellow, and 5 minutes old blue, and older than 10 minuets gray.

This would give the 1 hour view of activity, but cleary identifies those
that are still moving NOW...  And those few could be DR'd?

Just kibitizing...

Bob, WB4aPR





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