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[aprssig] Re: The best resolution of position from APRS

Robert Bruninga bruninga at usna.edu
Thu Jan 5 22:56:01 UTC 2006


>>> kc2mmi at verizon.net 01/05/06 3:52 PM >>>
>even today most map software companies refuse 
>to address. They continue to show "pinpoint" 
>resolution, when they should be using position 
>circles that are much larger blobs. AFAIK all of
>the APRS software authors... make this same
>deception, on purpose.

No, this has been in APRSdos from the beginning.
When APRSdos is replaying an GPS track in its map-
drawing utility it displays the position as a circle of
about 60 foot radius.  At most zooms it makes just
a dot.  But if you zoom into ranges below about the
2 mile scale you will begin to see it.  And can zoom 
all the way in to where it is at least the size of a 
quarter on most screens.

This was so that people would not just blindly "connect
the dots when drawing APRSdos maps from live GPS
data.

APRSdos alsol does this in all versions for the 0.1,
1, and 10 mile ambiguities.  You wont see the circle
until you zoom in below the scale where the SYMBOL
is no longer larger than the ambiguity area.  At that
range-scale and below, the symbol disappears and 
only the circle remains and continnues to expand as 
you zoom in.  The callsign remains inside the circle.

Thus there is never any confusion on the part of
the recepient as to the accuracy of the position.

But you are correct.  APRSdos does not do this
for position ambiguities below 60 feet...

Bob, WB4APR

 Including MS and Google, and the latter should certainly
know better than to intentionally mislead users. Even DeLorme (who I have mixed
feelings about) gave users the option to use three different sized circles for
their GPS position, so that SOME indication of position error is possible.


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