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[aprssig] /A= altitude question

Bob Bruninga bruninga at usna.edu
Sun Aug 8 00:26:06 UTC 2010


For what it is worth:

The /A=XXXXXX altitude protocol is *not for antennas*.  It is for balloons and aircraft.  Altitude means nothing by itself to radio range.  That is what PHG data is for.

I see far too many stations cluttering up the air with useless /A=XXXXXX entries...

Bob, WB4APR


---- Original message ----
>Date: Fri, 6 Aug 2010 21:48:16 -0700
>From: aprssig-bounces at tapr.org (on behalf of Greg Clark <k7rkt at bigredbee.com>)
>Subject: Re: [aprssig] /A= altitude question  
>To: TAPR APRS Mailing List <aprssig at tapr.org>
>
>   Guilty as charged -- negative altitude numbers are
>   not something I have a lot of experience with.
>    I'll take a look at it, but living at an altitude
>   of 100+ meters ASL, it's a little difficult for me
>   to 'simulate' without driving to the coast myself.
>   I'd recommend ignoring those numbers as well if you
>   can.
>   I *have* noticed that when my unit powers up, it can
>   generate some strange altitude numbers for the first
>   packet it transmits -- any idea if this is an issue
>   related to powerup?  Or do you
>   see multiple packets that look like this -- if
>   you've got some more examples of malformed packets,
>   that would certainly help.
>   Regards,
>   Greg Clark   K7RKT
>   BigRedBee, LLC
>   On Fri, Aug 6, 2010 at 8:50 PM, Lynn W. Deffenbaugh
>   (Mr) <ldeffenb at homeside.to> wrote:
>
>     From aprs101.pdf (search for it and read a copy):
>
>     Altitude in Comment Text — The comment may
>     contain an altitude value,
>     in the form /A=aaaaaa, where aaaaaa is the
>     altitude in feet. For example:
>     /A=001234. The altitude may appear anywhere in the
>     comment.
>
>     No, /A=000-17 is not a valid altitude.  My client
>     would simply ignore it, and leave it in the
>     comment text because it looks for /A= followed by
>     a valid 6 digit number.  It does allow for a
>     minus sign and 5 digits, but NOT for a non-number
>     as this is.  If you know it's a BigRedBee, I'd
>     suggest contacting them to get their firmware
>     fixed.
>
>     Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows
>     Mobile and Win32
>
>     PS.  On the transmitting side, my client will
>     only transmit an altitude if it is greater than 0.
>      I know there are places on the planet where <0
>     is valid, but they are fewer and further between
>     than GPSs that indicate negatives when people are
>     driving around at or just above sea level.
>
>     VK6 UFO wrote:
>
>       G'day, I've just joined this mailing list so
>       apologies for questions that have already been
>       dealt with.
>
>       I'm writing a small program for local users
>       which can monitor local traffic (via AGW PE and
>       a receiver) and react to certain events.
>       One thing I've noticed is that there's no spec I
>       can find for altitude using /A=###### which
>       accounts for values below sealevel. I first came
>       across this when some mobile stations are
>       reporting like this:
>
>       2010-08-07 02:52:22 UTC:
>       VK6ZMS-9>APBL10,VK6KSB-3*,WIDE2-2,qAR,VK6GHZ:!3232.15S/11544.66EP236/000/A=000-17
>
>       VK6ZMS-9 is using a BigRedBee and no doubt his
>       GPS receiver is reporting his altitude below
>       sealevel. His location at the time was next to
>       the coast so it could be an error from his GPS
>       receiver or he may have actually been below
>       sealevel... I'm not familiar with the terrain
>       there. I've adjusted my software to allow for
>       this format anyway.
>       aprs.fi <http://aprs.fi> seems to treat reports
>       like that as not an altitude report so it ends
>       up in the comment text.
>       I guess my question is.. is this altitude report
>       valid or should it be something else? Is there
>       documentation somewhere that would clear it up?
>
>       Thanks.
>       --
>       ———————
>       Rob VK6UFO
>
>       ------------------------------------------------------------------------
>
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