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8351Re: Dead Reckoning (was: Instantaneous Course/Speed Vector)

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  • apenadragon
    Apr 1, 2011
      I actually witnessed this when driving home the other day, and happened to spot my DR icon moving in the opposite direction...

      it took me a few moments to sort out what was happening, I had an icon where the last beacon took place, I had my current location, and then I had this third icon at the end of the DR line, as my speed and direction changed the DR icon moved in relation to the last beaconed icon according to my CURRENT direction and speed... I imagine that if one were to go to a parking lot and drive in a large circle at the right speed they could get the DR icon to pass through a full 360 degree arc outside the actual current location....

      yeah, i need more sleep because that sounds amusing to go try...

      My thought is that DR works on the latest information available to the program in relation to course and speed... when receiving another station all you have is the information that it beaconed, or that was calculated, depending on how APRSIS is configured, so the DR line goes in one direction until expiration or a new beacon is recieved.

      When DRing your self, the program has updated information on course and speed every 2-5 seconds, and changes the DR line accordingly... Travel at 30mph, and then as soon as the beacon goes out, count to 5 and then come to a stop as if stopping at a stop light, you'll watch your DR icon travel backwards. Just dont' hit anything.


      --- In aprsisce@yahoogroups.com, Randy Love <rlove31@...> wrote:
      > Ah..
      > Well, you have the added benefit of dynamic dead reckoning because of data
      > direct from an attached GPS. :)
      > Lynn can confirm this, but the laptop at Wye road is what your GPS is
      > currently showing. The laptop at the top of the line is your last beaconed
      > position. And then the software is using that position to base your dead
      > reckoning projections, but appears that Lynn was sneeking and using
      > up-to-date GPS data for the ME dead reckon calculations.
      > That would explain what's happening. Lynn can confirm.
      > Pretty sneaky.
      > Randy
      > WF5X
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