[aprssig] APRS radios
bruninga at usna.edu
Tue May 27 15:40:57 CDT 2008
>> Third party and Objects is where I think the spec
>> overly complicated APRS. It was so simple. An object
>> is NOT a special packet with its own formats. It is
>> simply a position report of an object name that is
>> not a callsign. So the name has to be in the packet,
>> and not in the AX.25 header where the callsign is.
>> On receipt, all one was supposed to do was chop off
>> the header, and then use what remained (which now
>> contains a NAME instead of a call) as if it had been
>> received on RF directly. Just rearrange the name
>>into a pseudo packet and then continue parsing like
>> any other packet.
> Ok... what if the object has the '_' symbol? Do you
> interpret the 000/000 extension as wind direction and
> speed, as you would for a non-object packet?
Yes, it would be parsed exactly like any other packet with that
field. SO a WX packet can be transmitetd from a TNC with its
own station call in th eheader, or a weather report can be
transmitted as an object, with its name included in the data
field. But everything after the LAT/LONG should be parsed
identically, and handled the same. Though a reference to the
transmitting station needs to be retained so we can trace
> Or would it be course/speed, per the object report
> format on page 68? According to that, wind isn't
> one of the allowable extensions.
Yep, this is a spec error. An object once the NAME has been
extracted is supposed to be parsed like any other position
> This is exactly the sort of inconsistency I'm talking about.
> A formal grammar would specify exactly what can and can't go
Yep, instead of taking my original design which was verbally
presented as I have presented it above (an OBJECT should be
parsed identically to any other position format). The Techincal
author attempted then to do as you suggest, and that is
re-specifiy every possible field in an Object. Which in my mind
was not a good idea, as it could lead to omissions and confusion
as noted above.
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