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[aprssig] Appalachian Trail Tracking

John Gorkos jgorkos at gmail.com
Thu Mar 1 15:07:14 UTC 2012

Well… This is a bit harder than I though.  Average message rate through
APRS-IS is in the 40 msgs/sec range right now.  The way APRS-Alert is set
up, it first filters on call sign (I.e. It has a list of call signs that
people are interested in), and then it applies any geospatial rules on the
far more limited subset of interesting calls that get through, versus
against the entire message stream.
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.  So,
for special cases, I can check every position to see if it's coming from
someone on the Appalachian Trail (I created a polygon that encloses the
entire length of the trail to do a st_within() test against), but I can't
make a feature on the web site that allows people to say "notify me any time
ANY station enters zone X".   Same thing for another great idea I had:  sent
an APRS message or other notification (I.e. Sms, if the call sign is
registered) to any station entering an active Severe Thurnderstorm or
Tornado Warning box.  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,
especially on a night like last night, where we had multiple large swaths of
the US covered with blizzard warnings, tornado warnings, etc.
Granted, I'm not as committed to this financially as Hessu is with APRS.FI.
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

From:  John Gorkos <jgorkos at gmail.com>
Date:  Tue, 28 Feb 2012 10:13:02 -0500
To:  TAPR APRS Mailing List <aprssig at tapr.org>
Subject:  Re: [aprssig] Appalachian Trail Tracking

Usually, I'm pretty useless, but this sounds like something I might be able
to help with.
First of all, there is some pretty good GIS data for the A.T. Here:
That can be sucked into Postgres pretty easily.  Next, this would be a good
excuse to make some additions to APRS-Alert (that darned web site that I put
together that sends text messages/emails when a station enters or leaves a
zone).  Seems to me it shouldn't be too painful to do two things there:
1. add an upload option for shape files, or better yet, include a set of
pre-defined zones for people versus just a point/radius (I.e. States,
counties, lakes, NWS zones, etc)
2. Add a "log this data" option as opposed to a "send me a text message"
notification.  The use case is "Bob wants to collect all of the packets sent
from inside a specific zone  for the next 30 days."
> 1. Bob logs into the APRS-Alert web site and creates a new rule that says he's
> interested in all position packets sent from inside zone "Appalacian Trail"
> 2. On the Notification Page, he creates a new notification rule that sends him
> a reminder once a week of the data that's been collected, including a URL he
> can use to fetch that data.
> 3. When he clicks on the URL, he's presented a list of options for viewing the
> data, including KML, raw APRS, and maybe shape file.
Just brainstorming here.  Bob, does this sound like what you're looking for?
I'd have to place some limits on the data size and time limit for
collection.  Some yahoo is sure to set up a rule that says "record all
position packets in the state of california for the next 12 months" and
suddenly my 2TB drive starts looking pretty small.  I could probably do a
rolling window in time?  I don't want to tread on the territory of aprs.fi
and Hessu's work, but this seems like my niche.

John Gorkos

From:  "Lynn W. Deffenbaugh (Mr)" <ldeffenb at homeside.to>
Reply-To:  TAPR APRS Mailing List <aprssig at tapr.org>
Date:  Mon, 27 Feb 2012 16:27:53 -0500
To:  TAPR APRS Mailing List <aprssig at tapr.org>
Subject:  Re: [aprssig] Appalachian Trail Tracking

 On 2/27/2012 4:13 PM, Bob Bruninga wrote:
> Can you or Hessu think of a way to aggregate all this data into one 2000
> mile long string of data?  Or do we just collect callsign reports and then
> wait till we have enough data and then manually connect them?
 I've been playing around with OpenStreetMap data recently and they seem to
have the Appalachian Trail in as a way of connected nodes.  It'd be really
neat if there was an easy way to detect an APRS position report close to
this line to get an automated way of collecting points, but I'm not that
good with geo-relations in PostGreSQL (yet).  So for now, the only thing I
would know is to manually collect and connect reports as submitted by the
hikers using callsign and date/time range.
> Even if we came up with a clever SYMBOL or other flag to indicate the AT,
> the chances are that some will forget it and do it wrong, so we will end
> uphaving to manually connect the data anyway.
 Yeah, that's probably not even worth asking them to do, IMHO.  We'll get
more people telling us when they were there than we would people getting the
symbol right.
> So unless you have a clever idea, Im just going to ask everyone to REPORT
> their DATES and TIMES and CALLSIGN when they were actually on the trail andwe
> can aggregate it later?
 That's a good start.  If we have that information, we can always do it the
hard way.  If we miss capturing that data, we might miss our last chance to
get what you're after.
> How long is data retention in your data base of Hessu's before we have to be
> sure to capture the data?
 My DB is limited to 5 days (sufficient for my purposes), but I store all
raw packets forever (for now), so I could go back and resurrect paths if
necessary.  But I believe Hessu keeps posits in his DB for a LOT longer than
my 5 days and has some good queriability to boot.
> We will ask all hikers to use a 2 minute rate while hiking unless they are
> running Proportional Pathing, then a 1 minute rate is the same thing.
 Did AL0I-7 do one of your "destination" posits earlier today?  If not, then
he's backtracking for some reason today.  Hopefullly the    following screen
cap will come through.  His first posit was to the    SW, then he jumped to
the NE and is now working his way back.  Last posit was 1.75 hours ago.
 Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32
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