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

Robert Bruninga bruninga at usna.edu
Fri Jun 16 17:37:04 UTC 2006


>>> jdw at eng.uah.edu 06/16/06 9:16 AM >>>
>> Each different maping system has to be understood
>> by the code writer inorder to draw it on the PC.  Therefore he
>> should have an idea about the map accuracy
>
>What you just implied, Bob, is that if I create some horrendously 
>inaccurate APRSdos map, then it is _your_ fault, as the APRSdos 
>developer, for not telling the user...

Yes!... and that is why APRSdos automatically assigns ambiguity in
EVERY transmitted position based on the scale of the map in use
by the initiator of position information.

If someone sketches a map of his city by its city-limits line and a
few of the intersecting roads, then he will probaby be using this
map at say about a 32 mile scale or more to see the general
local area and surrounding activity.

If he places HIS station or any other object on the map at that
scale with his cursor, then APRSdos *automatically* gives his
station and or object, an appropriate ambiguity imbedded-in-the-
packet.  This is so that on RECEIPT by another station, the
lack of precision available at the SENDER is conveyed *and
displayed* unequivocally to all viewers.  In this case it would
have one mile ambiguity so that no one will inappropriately
assume any greater accuracy.

This was fundamtental to the concepts of the original APRS
since it was anticipated that everyone might be using different
map systems at different range scales and different map
quality.  Hence, avoidance of this problem was *built-into-APRS-
from-day-one* yet ignored by almost all follow-on clones.

It is a big disappointmet to me to see so much of the original APRS 
lost in translation to incomplete clones.  The biggest and most
fundamental examples are:

1)  Position ambiguity - to maintain integrity from sender to receiver
                                     across platforms
2)  Range scale - to provide a consistent means of describing maps
                            views across platforms
3)  Decayed Xmit algorithm for minimum latency and minimum QRM
4)  Display of the 8 attributes of a symbol on the map (not one
     dimensional featureless ICONS).
5)  PHG and RF network range and relative station performance
6)  Signal Strenght Contours for instant signal location (DFing)
7)  Display of ALOHA circle so user is aware of his RF network limits
8)  Cautions and warnings to user of bad paths and other selections
     that will impact others.  Network pretecting defaults.
9)  Smart Message acking so that dialog messages fly
10)  Transmission and display of active  HUMAN-PRESENT bit
11)  Fixed size virtual Bulletin Board with line-by-line editibility
12)  Dead reckoning so that moving objects keep moving and
       conveyed unambiguously to the viewer
13)  Initial capture of first packet from a station and tentative
       plotting in vicinity of his first digi so that he is known to the
       system until an eventual posit packet comes in.
etc...

Bob, Wb4APR






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