[aprssig] ALOHA and DIG-Hops plotter...

[Robert Bruninga]

I just added a utility to APRSdos that will plot all of
the surrounding digi's PHG circles in different colors
depending on the number of HOPS that it takes
for YOUR station to hit them....  See the plot:

http://www.ew.usna.edu/~bruninga/aprs/digihops.gif

This map was just an instantaneous snapshot. and is
a work in progress.  Some DX digis may have come in 
via a band opening, and  some close ones may  have 
had a fold-back path, so one should watch the map over 
time to get a sense of the real averages...

1) 3 hops will cover out 128 miles in all directions even
    here on the East Coast in most cases.

2) several digis dont have PHG circles because
    of errors in their set up

3) Some digis dont have PHG circles due to an un-found
    bug (that is why this is not releasable yet)

4) Many PHG circles are overly optomistic (sysops used
    height above sealevel instead of HAAT.

APRSdos does this plot by analyzing the path as 
heard from all digipeaters.  Thus if a digi was 
heard as VIA WIDE*,WIDE2-1, then this digi
position packet took 2 hops to get to you, so you
would take 3 hops to hit it's surrounding user area.  
It is this 3 hops that one would need, and that is what 
is plotted  on the map.

This APRSdos utility will be in the next release,
but needs to handle a few more exceptions first.
But I thought it was revealing and will be useful
to help users figure out what they need.

PARTICULARLY, I am going to also have this
utility overlay YOUR own ALOHA circle on the
map showing what coverageYOU should
only be trying to hit... based on your 50 nearest
neighbors.  That is your Aloha circle..

That will be a real eye opener!

Bob, Wb4APR