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[aprssig] Maps of APRS User Density!

Robert Bruninga bruninga at usna.edu
Fri Feb 11 22:03:34 UTC 2005


Here is some more data on the APRS User Density map:

http://web.usna.navy.mil/~bruninga/aprs/fix14439.html 

The cell size is 30 miles.  The highest density (red) is 115 users
per degree of LAT/LONG.  The blue area is between 12
to 25 users per degree.  But there are more than 100 times
more Blue cells than Red ones and 10 times more users
in the outer blue areas than in the overloaded cities.

So if you only go out 2 cells of BLUE from a RED cell
the packets from all the BLUE users in that ring flooding 
into the city is about equal to the number of packets from 
the users in the city.

So again, do not be fooled into thinking that the BLUE cells 
are not that big a contributor to QRM.  In fact, they are
the bigger contributor beacuse everyone that lives in the RED
cell knows to use WIDE2-2 or less to minimize the impact 
on his own area, but the 10 times more users out in the
boonies running 3-3 dont see the packets from the 2-2
users in the city and are not aware that they are flooding
the city with their too-long hops!

Thus, we still need user education that large hops even
in low density areas do more damage than their senders
can see or know...

de WB4APR, Bob

*** original message***

This was plotted using APRSdos and data provided by
Steve, K4HG.  It is very revealing!  At first glance it appears 
to support the frequent opinion " Bob, What you see back
east is not what we see!" comment.  But conversly, that goes
both ways.  "You dont see what we see here in Wash DC
either"

Also, you mgiht say, let the cities pound sand, look at all the
Blue States where we can run WIDE5-5 all we want.  Well,
think again.  There is probably no where in that sea of blue
where you can run 5-5 and not end up with packets hitting a
city, or even multiple cities!  And  The "blue area" around
say Dallas, contains over 2 MILLION square miles and even
*more users* than those that live in the RED dot.  

Yes, the Blue density is 10 times less, but is 100 times more
area.  This is what floods the cities networks!

THus, although the blue areas are sparse, if they use lots of 
hops, they hit the cities from ALL DIRECTIONS and FLOOD 
THEM.

THus, I think the New n-N Paradigm is on the right track.

1) Lets see if we can live with a national limit of 4-4 in the
    wide open areas and distant travelers and enforce it with
    traps of at least 6-6, and 7-7 and 5-5 if we can...
2) Lets let the high density areas add traps for large N's
    as needed to keep their nets from saturation
3) We must get rid of the W,W and W,W,W paths which 
    generate 3 to 5 times the number of dupes which is
    probably a bigger problem in most areas than WIDEn-N
    ever was.

Now we have the data.  Lets make it happen!

de WB4APR, Bob


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