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[aprssig] /A= altitude question

Greg Clark k7rkt at bigredbee.com
Sat Aug 7 04:48:16 UTC 2010

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.


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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