Weird GPS experience


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  1. Doit2it

    Doit2it Well-Known Member Contributor This Topic's Starter

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    I just had the weirdest experience with my Droid X GPS today. I was parked at a Sonic Drive In in Nashville, TN eating lunch. I decided to do a little Geocaching, so I opened the C:geo app to see what was near. The GPS showed locked, but it showed my flying at 40,000 feet above central Kansas. Based on the nearby caches, I was moving at about 0.1 miles per second (360 mph) and was loosing altitude of a few feet per second. I opened Google Maps and it showed the same location and movement. I was parked in Nashville, TN at the time. I rebooted and after 5 minutes of trying, I could not get a GPS lock (I assume it's because the last lock was over Kansas, and the GPS was looking for satellites from that location). I just tried again, and it took 3 minutes, but I finally got a correct lock with the GPS.

    It's fine now, so I'm not looking for answers. I just wanted to share that weird occurrence.


    [​IMG]
     

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  2. sitlet

    sitlet Banned

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    could have just been a bad sat reception.
     
  3. Doit2it

    Doit2it Well-Known Member Contributor This Topic's Starter

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    Yea, that's what I thought, but why did it show me moving (and at 40,000 feet) while I was parked approximately 650 miles away at 700 feet above sea level. I'm sure the phone (GPS program) was misinterpreting the GPS signal. The movement "may" have been a "reflection" of the satellite's movement. But GPS satellites are geosynchronous, so it couldn't be that. Not really sure. Just weird.
     
  4. gpsmapper

    gpsmapper Member

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    Most GPS satellites aren't geosynchronous. This is why there are good days and bad days for reception in marginal environments.
     
  5. nevergonnauseth

    nevergonnauseth Well-Known Member

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    i wonder, since you said you was parked at sonic and i know they have those metal awnings over their food ordering spots, maybe somehow the signal got caught in there and bounce around causing an anomaly?
     
  6. Doit2it

    Doit2it Well-Known Member Contributor This Topic's Starter

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    Yea, that may have been part of the problem as well. I was parked under the awning. I moved to another location and put my phone on the dash for the reboot and failed GPS lock. I think I just didn't wait long enough for a good lock. After that, I didn't bother trying to fix it. I figured it was a temporary issue. When I finally got a good lock, it was hours later, inside my home, while I was writing the original post.
     
  7. binary visions

    binary visions Well-Known Member

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    Superman? Is that you?
     
  8. bbuck002

    bbuck002 Well-Known Member

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    i disagree, GPS satellite calculations rely on the fact that they are in geosynchronous orbit. There may be some slight fluctuations with their exact position but they would have to stay within built tolerances. Most of the problems that arise from GPS satellites is when their clocks become unsynchronized. (due to the fact that time moves slower at their speed and position relative to the surface of the earth)
     
  9. nj02vette

    nj02vette Well-Known Member

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    You're free to disagree all you want, but GPS satellites are NOT geosynchronous. They orbit in Medium Earth Orbit, not Geostationary Orbit. Takes about 12hrs for one satellite to orbit the Earth.

    Wiki isn't the best source, but it's a good start.
    Global Positioning System - Wikipedia, the free encyclopedia
     
  10. bbuck002

    bbuck002 Well-Known Member

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    i stand corrected,

    tho the time aspect does cause problems too
     
  11. Doit2it

    Doit2it Well-Known Member Contributor This Topic's Starter

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    So the movement most likely wasn't a "shadow" of the GPS satellite. If my blip was moving at approx. 360 mph that would take 66.7 hours to circumnavigate the 24,000 miles of the earth (at sea level). GPS satellites complete 2 orbits per day per the Wiki. And that's at 12,500 miles above sea level. It was moving WAY too slow.

    It appeared as if I was watching an aircraft, but I know that's not the case. ACARS is VHF at 130Mhz while GPS is 1.2, 1.5, and 1.7 Ghz transmissions.

    I'd love to know what caused the error, but I'm sure it was something as mundane as a temporary memory error causing invalid computations. Boring!
     
  12. Steven58

    Steven58 Reformed PH VIP Member

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    It was accurate. The world is collapsing. WE'RE ALL GONNA DDDDDDDDDDDDDDDDIEEEE! ;) :)
     
  13. Jim Dawson

    Jim Dawson Well-Known Member

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    ACARS used to be ground based VHF only, it now uses VHF, SATCOM, and more recently, HF data links for polar routes where SATCOM isn't possible.
     
  14. mruno

    mruno Well-Known Member

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  15. Doit2it

    Doit2it Well-Known Member Contributor This Topic's Starter

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  16. cmathis

    cmathis Well-Known Member

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    Aliens.[​IMG]
     
  17. Dabitz

    Dabitz Well-Known Member

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    It got a lock on your twin soul...
     

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