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ZL3AI > APRDIG 10.05.04 19:37l 255 Lines 9082 Bytes #999 (0) @ WW
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Re: [ui-view] Ambiguity?
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Wed, 21 Apr 2004 17:35:12 -0400
X-Message-Number: 28
Im sorry, but you still are confusing APRS ambiguity bytes...
>>>"Curt, WE7U" <archer@eskimo.com> 4/21/04 1:08:54 PM >>>
>The correct method would be to leave all of the digits intact,
But if you have ambiguous position data *there-are-no-more-digits"!
You have got to clear your mind of thinking about MASKED or dropped digits.
That simply is not what APRS position ambiguity is all about...
Bob
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Subject: Re: [ui-view] Ambiguity?
From: "Scott Miller" <scott@opentrac.org>
Date: Wed, 21 Apr 2004 14:45:36 -0700
X-Message-Number: 29
>But if you have ambiguous position data *there-are-no-more-digits"!
>You have got to clear your mind of thinking about MASKED or
>dropped digits. That simply is not what APRS position ambiguity
>is all about...
So where do you put the center of your circle? If I'm reporting my position
as N34____ W120____ do I put the circle at N34 W120? How big do I make the
circle?
Scott
N1VG
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Subject: Re: APRS Kenwood Radios
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Wed, 21 Apr 2004 17:45:43 -0400
X-Message-Number: 30
>>>"KC2MMi" <kc2mmi@verizon.net> 4/21/04 1:57:36 PM >>>
>>Name me ONE thing that you think the Kenwood
>>Mobile Radio APRS capability is "holding back"
>...Well, two things if you can do them both.
>When the D7 is used with a headless GPS (i.e. hockey puck)
>can you make it display the position data and EPE
>data from the GPS?
Yes, easy. Buy a GPS with a display...
>All I want is to see the same DDD.MM.mmm that my
>GPS is putting out, on the radio.
Easy, just look at your GPS which should display that data easily...
The D7 is designed to be connected to a GPS that has a display if you want
to SEE the GPS data... That is not the fault of the radio if you chose to
buy a GPS with no display...
Bob
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Subject: Re: Kenwood MObile APRS
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Wed, 21 Apr 2004 17:50:45 -0400
X-Message-Number: 31
>>>"KC2MMi" <kc2mmi@verizon.net> 4/21/04 2:09:47 PM >>>
>With APRS now even a TT3 can support sending a status
>string once every ## transmissions. And both a primary
>and secondary configuration, with totally separate parameters.
Yes? So does the D7. It has 3 different cofigurations and the D700 has 5.
And both can set the status rate separately...
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Subject: Re: [ui-view] Ambiguity?
From: "J. Lance Cotton" <joe@lightningflash.net>
Date: Wed, 21 Apr 2004 16:54:45 -0500
X-Message-Number: 32
So Bob,
Are you saying then that (based on your past comments on this topic) when
an APRS user uses position ambiguity by not entering all of the digits in
the coordinate fields, the displaying program should assume that those
"digits that aren't there" are zeros and then just somehow visually flag
that the symbol's position isn't necessarily exactly where it is displayed
on the screen?
If so: why do you assume values when there are none?
If not: why would you use a circle to indicate the bounds of possible
"real" locations for the position?
The point is, if you don't know those "digits that aren't there", but you
still have to display a symbol SOMEWHERE on the screen, you MUST have some
way of showing ALL of the POSSIBLE positions where the item really is.
That's what ambiguity is: you don't know; it's ambiguous! You have to plan
for ALL POSSIBLE VALUES.
That means a rectangle would best define the area in which such a reporter
(who is being ambiguous) REALLY is.
Your own APRS text file repository talks about how this is what you do when
a position report uses gridsquares rather than lat/long. Why would it be any
different for "digits that aren't there" in a lat/long?
-Lance KJ5O
--
J. Lance Cotton, KJ5O
http://map.findu.com/kj5o-14
joe@lightningflash.net
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Subject: Re: Kenwood MObile APRS
<LYR36507-195569-2004.04.21-18.00.55--mikejp#videotron.ca@lists.tapr.org>
From: "Michael J. Pawlowsky" <mikejp@videotron.ca>
Date: Wed, 21 Apr 2004 18:16:05 -0400
X-Message-Number: 33
I'm new to this group and this is not at all what I was expecting.
It is becoming a size contest.
My *&#*&%( is bigger than yours!
<sigh>
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Subject: Drawing Ambiguity circles...
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Wed, 21 Apr 2004 18:15:12 -0400
X-Message-Number: 34
>So where do you put the center of your circle?
>How big do I make the circle?
In APRSdos, I draw the SYMBOL at the indicated position as long as the
symbol itself is larger than the actual ambiguity. As the person zooms in,
once below the point where the symbol graphics can no longer cover the area
of ambiguity, I either let the SYMBOL GROW in size so that it is always
representative of the ambiguity OR...
I Drop the symbol and draw a CIRCLE approximating the ambiguity. The
location of the circle is RANDOMIZED to within HALF the ambiguity distance.
This is so that if there are 6 people all reporting the same ambiguous
position, then they dont all appear as one circle... and are ALL distinct
in the general area...
Bob, WB4APR
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Subject: Re: [ui-view] Ambiguity?
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Wed, 21 Apr 2004 18:34:10 -0400
X-Message-Number: 35
>Are you saying then that ... when an APRS user uses
>position ambiguity by not entering all of the digits in
>the coordinate fields, the displaying program should
>assume that those "digits that aren't there" are zeros
**** Absollutely not. That is the whole point. If the sender does not
have those digits, then they DONT EXIST. THey are NOT 0. Any program that
ASSUMES that a position entered as 35 59 is the same as 35 59.00 is making
an error 99% of the time... (there are 99 other possible .xx digits, and
.00 is only ONE OF THEM)!!!
>and then just somehow visually flag that the
>symbol's position isn't necessarily exactly where it is
>displayed on the screen?
No, the missing digits DONT EXIST. and they are definately NOT 00's.
>If so: why do you assume values when there are none?
I dont. ANd it is why after 14 years of arguing this with the other
authors who see no difference between 38 59 and 38 59.0000 that I am
getting fed up..
>If not: why would you use a circle to indicate the
>bounds of possible "real" locations for the position?
Why not use a circle? When the circle is defined to mean: "this position
is not known to a position any more accurate than the approximate radius of
this circle".
>The point is, if you don't know those "digits that aren't
>there",
Whoaa!
But why not?!! That is exactly why APRS has the ambiguity format. To
CLEARLY and UNAMBIGUOUSLY transmit this LACK of digis from the SENDER to
the RECEIVER. Problem is so many of the follow-on-authors just ignored this
critical basis of APRS...
>That means a rectangle would best define the
>area in which such a reporter (who is being ambiguous)
>REALLY is.
No, a rectangle with straight sides and precise corners is not a good
display of ambiguity in my opinion because such a geometric shape implies a
PRECISE ambiguity and that is an oxymoron.
>Your own APRS text file ... says... thats what... you do
>when a position report uses gridsquares rather than
>lat/long. Why would it be any different for "digits
>that aren't there" in a lat/long?
SImple. Grid Sqaures are *precisely defined". If you are 30 feet into one
and wrongly report it, then that is not good practice...
Bob
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Subject: Re: [ui-view] Ambiguity?
From: "Scott Miller" <scott@opentrac.org>
Date: Wed, 21 Apr 2004 15:54:35 -0700
X-Message-Number: 36
>**** Absollutely not. That is the whole point. If the sender
>does not have those digits, then they DONT EXIST.
>THey are NOT 0. Any program that ASSUMES that
>aposition entered as 35 59 is the same as 35 59.00
>is making an error 99% of the time... (there are 99
>other possible .xx digits, and .00 is only ONE OF THEM)!!!
Ok, I'm not even debating this anymore. The system is flawed. To be
meaningful, you need to be able to report your BEST GUESS at your location,
AND your estimate of the degree of error. Let's say I know I'm about midway
between 34 and 35 degrees North. If I say 34_ or 35_, that implies an
entire degree of ambiguity, centered half a degree from my estimated
position. If I say I'm at 34 3_, that implies I know where I am within 1/6
degree, which isn't true.
Scott
N1VG
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