[aprssig] Position Ambituity in APRS!

Paul Williamson kb5mu at amsat.org
Thu Jan 10 01:47:51 EST 2008

> > If I have my Kenwood at home
>> (35 57.458N  083 33.430W) set to
> > POS AMB 4, it would transmit 35  .  N\083  .  W.
>The kenwood implementation for transmitting position ambiguity
>is not the recommended way to transmit position ambiguity.  It
>truncates.  So it will transmit a 60 mile ambiguous position at
>35N and 83W.  But you are actually 57 nautical miles north of
>that position, and so you will just barely be inside the 60 nm
>ambiguity circle.
>If Kenwood had rounded instead of truncating, then you would be
>very near to the center of the circle which would have been at
>36N and 83W.

And that would be good, right?

This is where you confuse people by saying "transmit the digits you know". In the example above, the person KNOWS the digits 35. Your shorthand recommendation, taken literally, would have him transmit those digits, 35 -- and that's why people think you want them to truncate. But what you really want him to do is transmit 36 -- rounding instead of truncating.

Maybe if you said "transmit the digits you want everybody else to trust" it'd be less confusing.

73  -Paul
kb5mu at amsat.org

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