[aprssig] /A= altitude question

[VK6 UFO]

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 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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