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8368Re: Dead Reckoning (was: Instantaneous Course/Speed Vector)

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  • apenadragon
    Apr 1, 2011
      I think I'm starting to get it now, I'm pretty sure the math its self would drive me batty at the moment, but I think I'm getting the concept... I'll be interested to watch it on the way home (thinking about making the YL drive home) and see what the differeces are between the DR icon, and the Red Dot.

      I like the DR feature, and I'm going to transmit course and speed normally, so I'll just deal with seeing the DR on my screen and say thanks for putting up with us unedumacated youngsters.


      --- In aprsisce@yahoogroups.com, "Lynn W Deffenbaugh (Mr)" <kj4erj@...> wrote:
      > On 4/1/2011 2:17 PM, apenadragon wrote:
      > > That may be, but the APRSIS32 does that on its own, does it really need to display that on your local map??
      > As a diagnostic aid, yes. As a game to play on long drives, maybe. For
      > non-interested parties, that's why you can turn it off.
      > > I guess that's the question, if you have your Red dot turned on, right now doesn't that show up in the same place as the DR for "Me" in its current configuration? (did go and read the Red Dot explanation on the wiki)
      > Nope, the scales are different. DR is in map scale miles. Red Dot is
      > in % of Genius / Forecast Error where the circle is 100%.
      > > if Lynn changes the DR of ME to the same as the DR for everyone else, ie last reported packet, I'm not sure what use that is to the originating station on a local map.
      > It shows the originating station where an outside observer would think
      > you are, relative to your desired maximum error in the red dot, and
      > actual forecasted position in the DR symbol.
      > > Genius is also set to beacon after a set time, or a set distance, or after changing direction so many degrees, all of those user configured. (if I'm understanding it correctly, which I may not be)
      > You are correct. The overriding current factor is what is displayed as
      > a percentage towards the beacon ("Transmit Pressure") in the APRS-IS OK
      > pane on the display as well as the bottom-most bar at the bottom of that
      > pane. Hit Transmit and you'll see that bar drop back to zero (left) and
      > start growing to the right and morphing from green to red based on the
      > displayed Transmit Pressure.
      > > So, my understanding at this moment is that the DR for ME is showing in the same place that the Red Dot would be, only with the DR Line and beacon icon.
      > Different scales as already mentioned, so they may be in the same
      > relative location as ME (I'm still not sure about that), but probably
      > different distances away.
      > > If the DR for ME is set to use the same information as the other stations, last reported packet, I'm not sure what purpose that would serve.
      > It shows you what other's would believe based on what you've told them.
      > > It's an interesting phenomenon... I'd like to see a way to turn off Red Dot (available) and DR for ME Only, and still leave DR for all other stations, regardless of if DR gets changed from its' current configuration or not.
      > To turn off DR for ME, you'll have to turn off Configure / Beacon /
      > CourseSpeed as I've coupled them together in the upcoming release.
      > Prior to that, if you have Screen / Dead Reckoning turned on, it'll DR
      > me. With the upcoming release, if you are beaconing CourseSpeed, then
      > you'll be seeing what you're leading others to believe. I think it will
      > be informative.
      > Of course, turning off Screen / Dead Reckoning turns it off for both ME
      > and others.
      > Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32
      > > Adam
      > > KC2ANT
      > >
      > >
      > >
      > > --- In aprsisce@yahoogroups.com, James Ewen<ve6srv@> wrote:
      > >> On Fri, Apr 1, 2011 at 10:35 AM, apenadragon<kc2ant@> wrote:
      > >>
      > >>>> So, I just need to fix ME's DR to use the last beaconed speed/heading
      > >>>> rather than the current GPS speed/heading and all will be well.
      > >>> Do you?? personally I don't see the issue... the DR is a projection of where
      > >>> the station "should" be...
      > >> Actually Adam, it sounds like you're missing the issue.
      > >>
      > >> If you take the last reported speed and heading and project that from
      > >> the last reported location, as time progresses, the dead reckoned icon
      > >> will move to where the station "could" be.
      > >>
      > >> The problem with what we are seeing is that Lynn is using the CURRENT
      > >> speed and heading, and projecting a possible location using that
      > >> information from the last reported location.
      > >>
      > >> Lets suggest that a position was reported, with a speed of 60 mph, and
      > >> a heading of 90 degrees. After one minute, the dead
      > >> reckoned position should be 1 mile east of the reported location.
      > >>
      > >> The way it is implemented, if I stop driving east after 30 seconds,
      > >> the DR position would return back to the last reported location. If I
      > >> were to turn south and drive for 1 minute at 60 mph (without sending
      > >> an updated position report), there would be a DR object 1 mile south
      > >> of the originally reported position.
      > >>
      > >> Now, if this instantaneous line were to originate from the current
      > >> location, it would still be wrong. The line leaving my current
      > >> location would not be a dead reckoned position, but rather a projected
      > >> location for a future position report based on the current speed and
      > >> course, projected into the future the amount of time since the last
      > >> reported position.
      > >>
      > >> When Lynn gets it straightened out, you'll see something interesting
      > >> happening. As Lynn said, if you continue in a straight line at a
      > >> constant speed, you won't see the projected icon. If the road turns,
      > >> or you change speed, then you'll see the projected (DR) icon continue
      > >> along the last reported vector. Once the Genius settings determine
      > >> that you've strayed too far, a new position report will be sent, and
      > >> the DR icon will start moving away from the reported position again.
      > >>
      > >> James
      > >> VE6SRV
      > >>
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