[Xastir-dev] Position accuracy

[Curt Mills, WE7U]

On Sun, 7 Dec 2003, Gerry Creager N5JXS wrote:

> I've seen Jack's response, but I've got to comment further.  The more 
> conversions we do, without telling the world what datum we're using the 
> more times someone's gonna misrepresent what the data mean.  We need to 
> see a new version of the compressed format that tells you what datum is 
> in use.  Perhaps this is something for Scott's OpenTrac project rather 
> than APRS...

APRS dictates WGS84, although many GPS's out there are set to NAD27
so that they more closely match the street maps people are using.
It's a real mess.  It'd be nice if the protocol allowed specifying
the transmitted datum, or at least have the clients convert to WGS84
for transmission.  Of course, that's on our RFE list, but we could do
it with the libraries at hand.

Also, in the code we often equate NAD83 and WGS84 as being equal, and
don't pay much attention to rounding errors and the like as it
doesn't make much difference for APRS use.  If we were to start using
Xastir for purposes needing higher precision, much of the code would
have to be revisited.

Most of the things mentioned by Jack don't require higher precision
than already supplied via Xastir though.

-- 
Curt, WE7U.				archer at eskimo.com
http://www.eskimo.com/~archer
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