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[aprssig] /A= altitude question

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Sat Aug 7 03:50:31 UTC 2010


 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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>
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