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[aprssig] findu.com Location off by 100 miles.

Curt, WE7U archer at eskimo.com
Mon Jun 5 16:05:04 UTC 2006


On Mon, 5 Jun 2006, Robert Bruninga wrote:

> Ah, but again that interpretation is not interpreting the sender's
> intent.  Position ambiguity means the sender is only sure of his
> position to some level of accuracy.  If he uses 1 mile ambiguity
> then it does not make sense to try to force precise "edges" of that
> unknown quantity to something too precise.
>
> THe circle simply communicates that the position is unknown
> below that resolution.  A square would be fine too, but both
> should not be interpreted as precise lines'in-th-sand...

A square would _not_ be fine, 'cuz it's a rectangle according to the
definition in the APRS spec.  Well, perhaps right at the equator it
could be a square.

I understand what you are saying above, but you _could_ interpret it
as precise lines in the sand if you're watching somebody drive along
and the ambiguity rectangle all of a sudden jumps in one direction.
You know they just crossed the line and are driving into the next
rectangle.

Yes, the math works that way in the spec.  If I watched someone
drive along a major road with ambiguity on, I could gauge fairly
well where they were by when the rectangles switched.

This appears to be to be one case where the original concept and the
spec definition don't jive too well.

--
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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