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[aprssig] Signal Locator WEB page

Robert Bruninga bruninga at usna.edu
Thu Apr 26 16:47:51 UTC 2007


> > Please see the OMNI-Dfin technique in APRS:
> > http://www.ew.usna.edu/~bruninga/dfing.html
> 
> One could do this with an Xastir instance hooked to 
> an internet feed, set up to do snapshots every XX 
> minutes.  Feed that snapshot to an Apache web server 
> and you've got it.

That would do it nicely.  But the final system would need to be
able to let the browser viewer to zoom anywhere in the world to
select which particular signal-search is in progress.

Actually, I think this would be a great feature on FINDU.  All
this CGI needs to do is:

1) Normal APRS maping/placment of stns/objs (like FINDU)
2) Browser access to translate and zoom (like FINDU)
2) The ability to Display PHG circles around selected stations
3) On any OMNI-DF object or station, draw the DFS circle and
color it according to the reported subjective signal strength.
It would be ideal if this coloring could be transparent.  

I couldn't use transparency in APRSdos, but I have a routine
that sorts all DFS circles and then draws the darker weaker
signal-circles first and then drawing the smaller and brighter
circles last.  This way, the overlaps are easy to see and
clearly indicate the highest probability of the signal source.

Steve says he cannot draw circles on Google maps, and that is
OK.  In fact, one only needs the crudest maps for these plots,
because it is not the real-earth/map domain that we are
plotting, but just areas of probability.  Once  one can visually
interpret these overlaps, then one could click-and-zoom to
google maps (without the circles, but toggling back and forth).

Again, this technique is only trying to locate the signal source
to a few miles quickly, the final DF can be done with Hihger
Tech equipment, or good operators that know how to DF with
simply their HTs and a paperclip.


> > Browser based stations could also enter their 
> > report on the same web page and add to the display 
> > of contours.
> 
> Xastir Can't do that though.  One would need a web page 
> form that then generated APRS packets which would then 
> get injected into the local Xastir server port.  

Yes.

Also, a callsign would be required, because
garbage-in-equates-to a garbage plot.  I think all DFS circles
should be marked with the call of the ENTRANT.  There is nothing
so bad to this system as someone with no clue about HAAT or who
doesn't understand the POWER of a not-heard report!  

A guy that turns on his HT for 1 minute, and reports NOT-HEARD
on a signal that only beacons once every 10 minutes, or who is
on the wrong frequency, or doenst understand the difference
between the input and output frequency of a repeater, or who's
rig is deaf as a post, but "it works for him" since  he can work
the repeater 3 miles away.. Etc...

Bob, WB4APR





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