[aprssig] The best resolution of position from APRS
bruninga at usna.edu
Tue Jan 3 16:19:50 CST 2006
>>> scott at opentrac.org 01/03/06 3:55 PM >>>
>> Would it not make sense that THE best accuracy would be
>> obtained by sending the RAW GPRMC string in its entirity ?
>Depends on your input format. Garmins ... protocol)
>send their position as double-precision... in radians.
>the OpenTRAC position format) is 32 bits and works
>out to around 2 cm resolution.
>The newer NMEA format supports extra precision
>- though I understand that caused some trouble with
>the Kenwoods when it started appearing.
That is not exactly correct as stated. All of the older
NMEA formats also allowed floating point precision
and supported positions down to 6 inches and all of
the kenwoods (except the very first D7's all of which
were recalled) all will decode that. So all radios on the
air can receive raw $GPRMC and $GPGGA sentences
on the air independed of precision.
What you are aluding to is the most recent NMEA183
version 3 (I think) that snuck in an additional digit
somewhere else in the protocol (not in the position)
which caused problems.
Just trying to clarify, though I might not have it
exactly right above either.
More information about the aprssig