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ZL3AI > APRDIG 24.10.06 10:38l 243 Lines 8589 Bytes #999 (0) @ WW
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Subj: [APRSSIG] Vol 28 #1, 1/2
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From: ZL3AI@ZL2BAU.#87.NZL.OC
To : APRDIG@WW
Today's Topics:
1. Dumb tracker question (Earl Needham)
2. Re: Dumb tracker question (Tyson S.)
3. Re: Dumb tracker question (Earl Needham)
4. RE: Dumb tracker question (scott_at_opentrac.org)
5. Re: Dumb tracker question (Robbie, wa9inf)
6. RE: Dumb tracker question (scott_at_opentrac.org)
7. Re: Dumb tracker question (Wes Johnston, AI4PX)
8. Re: Dumb tracker question (Richard Amirault)
9. PCSAT-1 Digipeats? (Bob Bruninga )
10. Re: Dumb tracker question (Wes Johnston, AI4PX)
11. Re: Dumb tracker question (Richard Amirault)
12. Software Defined Radios (Andrew Rich)
----------------------------------------------------------------------
Message: 1
Date: Sat, 30 Sep 2006 12:50:02 -0600
From: Earl Needham <needhame1_at_plateautel.net>
Subject: [aprssig] Dumb tracker question
A friend of mine runs a tracker as W5ROY-15, and when I see him on my
HamHUD, his heading is usually incorrect, sometimes by as much as 180
degrees.
Am I remembering correctly that some TNC's do something odd like that? Or
could it be something else that's causing this?
Thanks,
Earl
Earl Needham, KD5XB, Clovis, New Mexico DM84jk
------------------------------
Message: 2
Date: Sat, 30 Sep 2006 11:59:05 -0700 (PDT)
From: "Tyson S." <timbercutter_at_yahoo.com>
Subject: Re: [aprssig] Dumb tracker question
I was watching Scott drive North on highway 101 when he was testing the
new T2-135 and his heading was wrong most of the time. I don't know if
that is because of the tracker, or APRS-IS. When his heading should
have been something like 20-30 (NNE) is was something like 180 or 270
or some other weird direction.
------------------------------
Message: 3
Date: Sat, 30 Sep 2006 13:05:09 -0600
From: Earl Needham <needhame1_at_plateautel.net>
Subject: Re: [aprssig] Dumb tracker question
I don't think it's APRS-IS, as I've had it happen when Roy and I were
within a mile of each other. Strange...
Earl
------------------------------
Message: 4
Date: Sat, 30 Sep 2006 12:25:49 -0700
From: <scott_at_opentrac.org>
Subject: RE: [aprssig] Dumb tracker question
Could be. I was running in Garmin mode, and there may be a glitch in the
calculation. It comes from the GPS receiver in meters/second North and East
- takes a bit of math to get it to degrees and knots. The arctangent
function takes a lot of processor time and stack space, so it's a prime
candidate for weird glitches. I'll probably replace it with an
approximation when I get a chance. For APRS purposes, it doesn't need to be
accurate to more than a degree or so.
Scott
N1VG
------------------------------
Message: 5
Date: Sat, 30 Sep 2006 15:25:59 -0500
From: "Robbie, wa9inf" <mwrobertson_at_comcast.net>
Subject: Re: [aprssig] Dumb tracker question
scott_at_opentrac.org wrote:
>Could be. I was running in Garmin mode, and there may be a glitch in the
>calculation. It comes from the GPS receiver in meters/second North and East
>- takes a bit of math to get it to degrees and knots. The arctangent
>function takes a lot of processor time and stack space, so it's a prime
>candidate for weird glitches. I'll probably replace it with an
>approximation when I get a chance. For APRS purposes, it doesn't need to be
>accurate to more than a degree or so.
>
>Scott
>N1VG
Please explain that statement Scott, "For APRS purposes, it doesn't need
to be accurate to more than a degree"! A degree in any purpose seems to be
far out!! :-) What were you suggesting?
Robbie
------------------------------
Message: 6
Date: Sat, 30 Sep 2006 13:35:05 -0700
From: <scott_at_opentrac.org>
Subject: RE: [aprssig] Dumb tracker question
>Please explain that statement Scott, "For APRS purposes, it doesn't
>need to be accurate to more than a degree"! A degree in any purpose
>seems to be far out!! :-) What were you suggesting?
The heading calculation doesn't need to be more accurate than 1 degree,
because it's only reported to the nearest degree anyway. The standard ANSI
C trig functions work with double-precision floating point numbers (in
radians), which is way more precision than I need.
Scott
N1VG
------------------------------
Message: 7
Date: Sat, 30 Sep 2006 20:18:13 -0400
From: "Wes Johnston, AI4PX" <wes_at_kd4rdb.com>
Subject: Re: [aprssig] Dumb tracker question
If the heading is 180 degrees wrong, maybe turning the GPS antenna on the
car so that the cords comes out near the rear of car will help and correct
the heading? lol.... couldn't resist!!!
We once convinced a local ham (actually an extra, and silent key now) that
the phasing element on a ringo ranger made it directional and he mounted it
on top of his rotator. We of course had him rotate it and gave him varying
signal reports.
Wes
------------------------------
Message: 8
Date: Sat, 30 Sep 2006 20:27:49 -0400
From: "Richard Amirault" <ramirault_at_verizon.net>
Subject: Re: [aprssig] Dumb tracker question
----- Original Message -----
From: "Wes Johnston, AI4PX"
Subject: Re: [aprssig] Dumb tracker question
>If the heading is 180 degrees wrong, maybe turning the GPS antenna on the
>car so that the cords comes out near the rear of car will help and correct
>the heading? lol.... couldn't resist!!!
(snip)
Not as far fetched as you might think. Many handheld GPS units will give
BEARINGS to waypoints that are 180 deg off if they are not held properly..
that is face up with the "top" of the unit towards the direction of travel.
For instance if you set the GPS screen to show you an ARROW that points
toward the waypoint (that tell you the direction you need to travel to reach
that waypoint) if you reverse the orientations of the GPS in your hand (put
the "top" of the unit facing you instead of facing the direction of travel)
the arrow will point 180 degrees in exactly the opposit direction you need
to go. Similarily, if you leave the orientation of the GPS alone and just
walk backwards.. or, if in a vehicle, drive backwards, the same thing will
happen.
I discovered this when I was an active Geocacher some time ago.
Richard Amirault N1JDU Boston,
MA, USA
n1jdu.org "Go Fly A Kite"
------------------------------
Message: 9
Date: Sat, 30 Sep 2006 21:00:05 -0400 (EDT)
From: "Bob Bruninga " <bruninga_at_usna.edu>
Subject: [aprssig] PCSAT-1 Digipeats?
>Not sure why, but my car isn't showing up on
>pcsat.aprs.org but it is showing up on the
>APRS-IS normally...
>
>KB0JQO-8>T2PS0U,PCSAT-1,WIDE1*,WIDE2-2,qAo,KC0RWZ:
>'xS l ^>/]"71}
That is because the PCSAT web page uses the PCSAT-1* as a way of knowing
the packet was relayed by PCSAT. But when you use the WIDEn-N method of
digipeating, then the * is not applied to the PCSAT-1 but to the used-up
WIDE1-1 in your path.
So to really be seen on the PCSAT web page, people have to use the non-n-N
digipeating such as RELAY, WIDE, APRSAT, ARISS...
de WB4APR
------------------------------
Message: 10
Date: Sat, 30 Sep 2006 22:39:27 -0400
From: "Wes Johnston, AI4PX" <wes_at_kd4rdb.com>
Subject: Re: [aprssig] Dumb tracker question
You are correct.... I'd forgotten that some GPS units contain an internal
magnetic compass. Usually there is a setting that is adjustable that allows
the compass to work when the speed is below XX mph.
Wes
On 9/30/06, Richard Amirault <ramirault_at_verizon.net> wrote:
>
>----- Original Message -----
>From: "Wes Johnston, AI4PX"
>Subject: Re: [aprssig] Dumb tracker question
>
>>If the heading is 180 degrees wrong, maybe turning the GPS antenna on the
>>car so that the cords comes out near the rear of car will help and correct
>>the heading? lol.... couldn't resist!!! (snip)
>
>Not as far fetched as you might think. Many handheld GPS units will give
>BEARINGS to waypoints that are 180 deg off if they are not held properly
>..
>that is face up with the "top" of the unit towards the direction of travel.
>For instance if you set the GPS screen to show you an ARROW that points
>toward the waypoint (that tell you the direction you need to travel to reach
>that waypoint) if you reverse the orientations of the GPS in your hand (put
>the "top" of the unit facing you instead of facing the direction of travel)
>the arrow will point 180 degrees in exactly the opposit direction you need
>to go. Similarily, if you leave the orientation of the GPS alone and just
>walk backwards.. or, if in a vehicle, drive backwards, the same thing will
>happen.
>
>I discovered this when I was an active Geocacher some time ago.
------------------------------
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