[aprssig] Just how does one set pos ambiguity?

Robert Bruninga bruninga at usna.edu
Wed Apr 30 16:38:03 EDT 2008

> Just how does one set pos ambiguity?
> I would like to [set position ambiguity 
> on] my two digi sites.

Instead of using DDMM.mmN/DDDMM.mmW, replacing the "mm" in both
latitude and longitude with spaces will give you 1 mile
ambiguity.  APRS has always supported the display of position
only to the precision that the sender enters in the first place.
Use SPACEs for any digits you don't know or don't care to
provide.  This gives you the option of 0.1, 1, 10 and 60 mile

See the web page about 50% down:

> Will it move around on my APRSDOS software 
> screen everytime it TX a POS report?

Depends on your zoom level.  If you are zoomed below the level
where the size of the symbol is no longer larger than the size
of the ambiguity, then yes, the symbol will disapplear and be
replaced with a circle.  And the center of that cirle may be
randomly displayed within that mile of ambiguity.  This
randomness is so that if there are multiple stations reporting 1
mile ambiguity all within the same 1 mile area, then they are
not all plotted on top of each other.

But few of the other clones (to my knowledge) take this care in
preserving the senders ambiguity to all viewers.  Some just plot
them -precisely- at the corner of the box or at the center of
the box (which does not convey the original nature of the
senders intent and quite defeats the purpose of "ambiguity" in
the first place).


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