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Thread: Tracker Details

  1. #51
    Join Date
    Jul 2012
    Posts
    6

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    There is no way to "fix" this. All we have to work with is the data received from the boat. In this cases it appears that DE send an incorrect position on 6/30 at 4:49AM. The following position at 8:48 having the correct position - hence the variation in the reported COG and SOG around those two points.

  2. #52
    Join Date
    Sep 2007
    Posts
    2,866

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    Ray, thanks for all this new info! More to watch.
    Last edited by BobJ; 07-01-2018 at 11:57 AM.

  3. #53
    Join Date
    Sep 2007
    Posts
    351

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    Quote Originally Posted by pogen View Post
    Look at the average speed over the course of an hour instead.
    That would work if the trackers actually worked; Double Espresso's tracking device certainly isn't performing up to snuff and produces various interesting position reports which in turn confound the folks trying to make sense of the data. It's also time-consuming to go backwards through the tracker data to locate the position reports for a specific time in order to make the calculations on a time average that's useful. But it's hardly the tracker display page's problem that Double Espresso's tracker is acting up.

    The tracker data page is supplying two data elements that aren't relevant, and in my opinion are incorrect: COG/SOG (presented as if it were at the moment the tracker sent a report), and 24 hour run (presented as if it were distance made good towards the finish).

    for example:
    247 Degs at 6.71 Kts
    Last: 24 HRS 183.1 NM at 7.6 KTS

    What would be useful is COG/SOG at the time of position report - that would tell the audience something about current conditions on board. As it is, COG/SOG is just a calculation to handle advance over time between two points and doesn't contain any additional information beyond the Lat/Lon position reports. If the tracker messes up (as Double Espresso's does) then you get silly COG/SOG results.

    The relevant 24 hour run data on a long race like this with various course options is distance made good towards the finish. The 24 hour run as presented in the tracker can tell you how much water the boat has sailed through; an artifact of this approach is that the more tracking points a boat produces the further that boat will have sailed through the water. But that doesn't tell you anything about how the boat has performed relative to any other boat in terms of getting to the finish line. Distance made good does provide data that can be compared across boats.

    As an aside, I run Beetle's instruments on 8-second rolling averages, the value displayed in the cockpit are those rolling averages - this seems to be enough to dampen out changing GPS COG/SOG, boat speed, course, and wind speed/angle to produce information I can work with (though I do miss out on the high and low values).

    - rob/beetle

  4. #54
    Join Date
    Aug 2014
    Location
    San Diego
    Posts
    74

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    "Tracker Details" seems like a good place to post this. Jacqueline was giving Dolfin the "doggy handshake" pretty much all the way across until pulling ahead at the end. I could see Mike on AIS the whole race but I don't transmit so he couldn't see me yet stayed right on my tail. Two days before the finish he crossed my track just 100 yards ahead after 1900 miles at sea. Here are some of the screen shots I took after realizing I couldn't shake him.

    Name:  Jacky0627.png
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    Name:  Jacky0629.png
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    Name:  Jacky0701.png
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