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[aprssig] aprssig Digest, Vol 51, Issue 5

Robert Bruninga bruninga at usna.edu
Thu Sep 4 14:11:43 UTC 2008


>> K3TAL-10 is a Winlink RMS Packet Gateway.  
>> The object is created by the Winlink system 
>> to alert Hams in the area of the gateway.  
>> The design is to not pin-point the exact 
>> location of the station...
>
> It is a little irritating that it shows up...
> in the main shipping channel through the center 
> span of the Bay bridge. 

These problems would not happen if all clients properly
implemented the fundamental APRS position ambiguity function.
The above object is being transmitted with 0.1 mile ambiguity.
For this application, I would think that one-mile ambiguity
would be more appropriate.  Then it could be located closer to
where it actually is, instead of randomly placed in the center
of the Chesapeak bay.

Secondly, many clients do not properly show ambiguous positions.
Fixed-size-ICONS were never intended to be displayed below the
zoom level where the size of the ambiguity is larger than the
size of the ICON.  At those zoom levels, the ICON must either
expand to cover the area of ambiguity or disappear and be
replaced with an ambiguity circle of approximately the area of
ambiguity.

This way, there is no chance for missinterpretation by
observers.  It is too bad that most clients never implemented
this fundamental ambiguity display principle of APRS.

> Oops - I just noticed it seems to be an Internet-
> only position, and not over-the-air. 

Then the operator has not made contact with the local IGATE to
request that this object be re-directed to local RF.  The value
of these Winlink and IRLP, and Echolink objects are for the
mobile and traveler and portable operator.  If they are not
going to RF where they should, then we are not providing the
local INFO to users as intended by APRS.

See www.aprs.org/localinfo.html

Bob, WB4APR









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