Duplicate position packet

[Lynn W Deffenbaugh (Mr)]

Just a curious question:

How far back do you look for duplicate positions as reported below? And
is there a limit to how many intervening positions may be present?

2013-07-15 08:40:27 EDT:
KG4IYP-7>S5TX8P,KD4PBS-3,KB4ZIN-5,WIDE2*,qAR,KB4YFK:'jNWl "k/]"5/}
2013-07-15 08:54:51 EDT:
KG4IYP-7>S5TX7Y,KD4PBS-3*,WIDE2-1,qAR,K4JH-2:'jNWl!Wk/]"5+}
2013-07-15 08:59:53 EDT:
KG4IYP-7>S5TX8P,KD4PBS-3*,WIDE2-1,qAR,WW4DC:'jNWl![k/]"5*}
2013-07-15 09:00:20 EDT:
KG4IYP-7>S5TX7Y,KD4PBS-3,KB4ZIN-5,WIDE2*,qAR,KB4YFK:'jNWl!Wk/]"5+}
[Duplicate position packet]

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

[Lynn W Deffenbaugh (Mr)]

(Added a nearly 5 minute example)

PS. Here's another much longer time gap example:

2013-07-15 08:53:34 EDT:
KI4OOG-9>APTT4,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:>/TinyTrak4 Alpha
2013-07-15 08:59:42 EDT:
KI4OOG-9>S5QW6Y,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:`q[.l#Sk/"6I}HMC (FMF) J.
Martin - Contact on 146.790
2013-07-15 08:59:45 EDT:
KI4OOG-9>APTT4,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:>/TinyTrak4 Alpha
2013-07-15 09:00:11 EDT:
KI4OOG-9>S5QW6W,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:`q[-lS>k/"6E}HMC (FMF) J.
Martin - Contact on 146.790
2013-07-15 09:00:17 EDT:
KI4OOG-9>APTT4,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:>/TinyTrak4 Alpha
2013-07-15 09:00:29 EDT:
KI4OOG-9>S5QW6T,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:`q[,lq~k/"6F}HMC (FMF) J.
Martin - Contact on 146.790
2013-07-15 09:00:38 EDT:
KI4OOG-9>S5QW6R,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:`q[+l].k/"6G}HMC (FMF) J.
Martin - Contact on 146.790
2013-07-15 09:00:48 EDT:
KI4OOG-9>APTT4,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:>/TinyTrak4 Alpha
2013-07-15 09:01:21 EDT:
KI4OOG-9>APTT4,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:>/TinyTrak4 Alpha
2013-07-15 09:01:28 EDT:
KI4OOG-9>S5QW5W,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:`qZ<0x7f>lpNk/"6N}HMC
(FMF) J. Martin - Contact on 146.790
2013-07-15 09:01:58 EDT:
KI4OOG-9>APTT4,N4YH,WIDE1*,WIDE2-1,qAo,KG4FZR-7:>/TinyTrak4 Alpha
2013-07-15 09:02:02 EDT:
KI4OOG-9>S5QW6W,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:`qZxm51k/"6M}HMC (FMF) J.
Martin - Contact on 146.790
2013-07-15 09:02:38 EDT:
KI4OOG-9>APTT4,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:>/TinyTrak4 Alpha
2013-07-15 09:02:47 EDT:
KI4OOG-9>S5QW6V,WIDE1-1,WIDE2-1,qAR,KA4EMA-3:`q[,l^ek/"6L}HMC (FMF) J.
Martin - Contact on 146.790 [Duplicate position packet]
2013-07-15 09:03:11 EDT:
KI4OOG-9>APTT4,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:>/TinyTrak4 Alpha
2013-07-15 09:03:42 EDT:
KI4OOG-9>APTT4,N4YH,WIDE1,W4LAW-6*,WIDE2,qAR,K4TQL-7:>/TinyTrak4 Alpha
2013-07-15 09:03:53 EDT:
KI4OOG-9>S5QW5T,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:`qZRn*mk/"6C}HMC (FMF) J.
Martin - Contact on 146.790
2013-07-15 09:03:57 EDT:
KI4OOG-9>S5QW5V,N4YH,WIDE1*,WIDE2-1,qAR,WM4RB:`qZOn>Ck/"6B}HMC (FMF) J.
Martin - Contact on 146.790 [Rate limited (< 5 sec)]
2013-07-15 09:04:10 EDT:
KI4OOG-9>S5QW6Y,N4YH,WIDE1*,WIDE2-1,qAR,KA4EMA-3:`q[.l#Sk/"6I}HMC (FMF)
J. Martin - Contact on 146.790 [Duplicate position packet]

[Heikki Hannikainen]

On Mon, Jul 15, 2013 at 4:06 PM, Lynn W Deffenbaugh (Mr)
<ldef...@gmail.com> wrote:
> Just a curious question:
>
> How far back do you look for duplicate positions as reported below?

31 minutes.

> And is
> there a limit to how many intervening positions may be present?

No.

The duplicate packet check is for relatively exact coordinates
(degrees with 5 decimals) concatenated with altitude and course.
Moving stations with GPS very rarely come back to the *exact* same
spot, while same course and altitude (given some GPS wandering).

If the new position is the same as the previous position, I just
update the "last seen here" timestamp of the previous position instead
of inserting a new database row. That's not counted as a duplicate.
Saves a lot of disk space and memory.

When a non-moving station is drifting around due to bad GPS fix, the
dupe checker also drops some packets. Not a bad thing actually, given
my storage/memory constraints.

- Hessu