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[aprssig] Re: TIGER maps what-s the problem?

Robert Bruninga bruninga at usna.edu
Sat Jun 17 22:06:46 UTC 2006


>>> ve7gdh at rac.ca 06/17/06 3:35 PM >>>
>> 1)Some client programs will ignore a station until it sends a posit.
>> 2) The current APRS-Internet Filterning systems (I think)
>> will not recognize a message sending station until it sends a posit.
>
>... from UI-View,... I changed my callsign ... deleted the position 
>and then re-connected and sent a message. Checking on 
>findu.com, my message showed up there. 

Ah, THe problem is when you SEND a message from a new
location and someone then tries to send you back
an ACK or a REPLY from the APRS-IS.  Most APRS-IS
servers will not allow the messages to flow back to 
the local IGate if the reported position for that sending
station is not valid or is not in the filter list of the local
IGate.

Thanks for the test, but your test did not test that function.  
Yes, everything gets to FINDU.  But only messages go
back to RF if an IGate recognizes a local station AND
the SERVER that it is connected to recognizes the
station as within the range filter of that IGate.

>UI-View doesn't completely ignore a position-less beacon, 
>but it won't place a station on the map without a position 
>and it won't show up on the station list. 

WIthout being in the station list, doesnt that prevent the
callsign from being recognized for most other functions, such
as search or find, etc?

>how many hams... are involved in APRS and both don't 
>have a GPS and couldn't guess within one degree what 
>their lat / long was? 

I have several D7's and almost NEVER use a GPS, for 
routine operations, because it is just too big a hassle.
But I DO message frequently from the D7.  And if I visit
a new area, I must manually enter a posit or it will not
transmit.

> to give an ambiguous position a try in UI-View, I tried 
>entering just the degrees and UI-View filled in 
>all zeros for the missing digits. 

That makes it a precise position, when you the sender
did not intend it to be at that precise location.  What if that
precise location is in a bordello and  your wife  is checking
to see that your airplane landed in St Louis?

That is the kind of problem that should not exist in
APRS, or any kind of GIS system.  The integrity of the
ambiguity of the source of data should be maintained
all the way through the system to any viewer.  This
was fundamental to APRS, but some programs ignored
it.  Thus, users of those progams should be aware of
the potential for missinterpretation...

And hopefully authors of future code will include this
fundamental in their programs.

Hope that clarifies the issues.  thanks

Bob, Wb4APR






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