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[aprssig] The best resolution of position from APRS

Curt, WE7U archer at eskimo.com
Tue Jan 3 17:42:56 UTC 2006


On Tue, 3 Jan 2006, Robert Bruninga wrote:

> >>> scott at opentrac.org 01/03/06 10:36 AM >>>
> >> Bob said that no one should use it at all, lest the be
> >> tempted to use it on an Object or Item which wouldn't be
> >> decoded by the  Kenwoods.
> >
> >That's OK... in a few months, everyone can just
> >buy one of my new trackers.=]  They'll already
> >do compressed items/objects...
> > Doesn't bother me at all if Kenwood doesn't want
> >to fix their firmware!
>
> Scott, remember we went through all this when you
> first came to APRS and wanted to change everything
> with an all new protocol.  It is not Kenwood you would
> be screwing up, it is 10,000 existing APRS users of
> kenwood radios.

Not true.  The OpenTrac protocol does not screw up any kenwood
radio to the best of my knowledge.  An OpenTrac packet appears to be
yet another packet that the Kenwood doesn't decode so it drops it.
Same for most APRS applications, they just drop it.  One APRS app
does decode them properly though.


> Compressed objects were obsoleted in APRS1.1.
> We know that the 10,000 kenwoods out there do
> not properly display the object name of a compressed
> object.  There is nothing going to change that.
> And since 85% of all mobile users that RECEIVE APRS
> data and display it while mobile use the kenwoods,
> it makes no sense to use it.

I disagree.  There are some wonderful uses for it which have been
discussed here before.  Don't just pick on Scott for putting out
Base-91 compressed protocols:  Xastir also generates/decodes it (and
a lot of users are using it) plus I think UI-View decodes it
properly as well.


> Having you put into your trackers  the ability to
> generate obsolete and unsupported compressed
> objects is just putting a time-bomb into the APRS
> system that will just guarantee that 85% of all mobile
> operators won't see them if an open-tracaker
> happens to unknowingly use it.

What if it doesn't matter to the particular operation in progress
whether a Kenwood APRS radio decodes it?  We don't happen to have
any Kenwood APRS radios (that I know of) in our SAR units.
Therefore it's a don't care.  In fact, we could switch over to a
full OpenTrac system pretty easily also.  We probably won't, but
who knows what the future will hold or what way-cool SAR-useful
devices might appear?


> Last time this came up, we presented a modification
> to the EXISTING formats that would be 100%
> backwards compatbile to all existing software,
> hardware and firmware, yet would give finer
> resolution down to a foot.  ALSO and of equal
> importance it included the DATUM as well.  SInce
> in my opinion, sending that kind of precision is
> useless if the datum is not included.

How many APRS applications have implemented this new method?


> If users need greater precision, use that option.
> not the obsolete compressed object format.

I personally find this new format to be a kludge, while the Base-91
compressed format is concise and useful.  It was in the spec for
years and was implemented in several pieces of software/firmware.
Just because it fell out of favor by a few doesn't make it less
useful or less used.

If the Kenwoods had an upgrade program to fix bugs and extend their
usefulness on into the future we wouldn't have to keep adding kludge
upon kludge or try to eliminate unimplemented options from the spec.
Just think of what the Kenwoods could become if they had upgradeable
firmware!  Oh yea, they do!  So how come we can't put pressure on
Kenwood to update them a bit?

--
Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
"Windows:  Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me:  I picked the coordinate system!"




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