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[aprssig] Appalachian Trail Tracking

Stephen H. Smith wa8lmf2 at aol.com
Thu Mar 1 18:10:54 UTC 2012

On 3/1/2012 10:07 AM, John Gorkos wrote:
> Looking for "all stations in a geographic area" means that every position 
> report needs to be geospatially tested against every zone that we find 
> interesting.  Right now, my setup takes about 3ms per "within" test, meaning 
> theoretically, I could do about 8-10 zone tests per message per second.

> Again, unfortunately, the math works against me:  testing every inbound 
> position against every active severe weather zone is more computationally 
> intensive than I'm willing to throw hardware at

> I'm sure I could get an amazon cloud instance, or put "real" hardware in a 
> "real" datacenter that could keep up.  I might yet do that, since I have 
> access to said hardware and colo, but for the immediate future, it's harder 
> than it looks.
> John Gorkos

How do the JavAPRS port 14580 filters do this?  (Extracting a very limited 
subset of the APRS-IS firehose.)   I would think that by the time an APRS 
server has 50-100 users connected, each with various different combinations of 
filter expressions, there must be an awful lot of these types of calculations 
going on.

Or is it that the rather simple geometric figures (simple rectangles and 
circles of x radius) involved in the port 14580 calculations are just so much 
simpler that an irregular polygon with a large number of points for the trail?



Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

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