 Topic Name: GPS scrambling
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on: January 11, 2010, 09:19:43 AM
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DaveH
Moderator
Posts: 975
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« on: January 11, 2010, 09:19:43 AM » |
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A couple weeks back I had some strange experiences with a Garmin Oregon 550. Basically, it told me it had a lock on satellite signal but but it was off by as much as a mile. Since I was using it to get to trailhead I wasn't familiar with it made for "interesting" bushwhacking  It was off by roughly 1/2 mile for 10-15 minutes. That's the first time I've seen this in a GPS. Anyone else ever experience similar GPS behavior? I figured the military scrambled the signals for some overseas operations  |
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Topic Name: GPS scrambling
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Reply #1 on: January 11, 2010, 10:51:34 AM
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DiDaDunlop
Posts: 45
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« Reply #1 on: January 11, 2010, 10:51:34 AM » |
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Nah I think scrambling such a wide area will affect more people than do good.
Maybe one of the satellites had an off day. Those satellites are getting old and they need to be replaced pretty soon.
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_ Bikepacking in the not so hilly Netherlands_
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Topic Name: GPS scrambling
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Reply #2 on: January 12, 2010, 05:11:45 AM
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willapajames
Location: Stowe, Vermont
Posts: 20
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« Reply #2 on: January 12, 2010, 05:11:45 AM » |
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Were you near a millitary facility? I've worked on some millitary research facilities for my job (I'm a geologist), and I've seen cell phone signals be completely tweaked out on the site, and 5 bars offsite. I know they're different satellites, but maybe some facilities have some way to block or distort signals.
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"All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity: but the dreamers of the day are dangerous men, for they may act their dreams with open eyes, to make it possible." - T.E. Lawrence
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Topic Name: GPS scrambling
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Reply #3 on: January 12, 2010, 05:23:00 AM
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bmike-vt
Location: Horgen, Switzerland
Posts: 1122
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« Reply #3 on: January 12, 2010, 05:23:00 AM » |
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Cell phone - land based towers
GPS - satellite based
Depending on how many satellites the OP had access to it can affect accuracy. The more the better chance of getting accurate results. At certain times of the day based on location and terrain a signal can fade. I'm not sure having a read of only 1 satellite as mentioned would provide any sort of accuracy.
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Topic Name: GPS scrambling
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Reply #4 on: January 12, 2010, 06:02:52 AM
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DaveH
Moderator
Posts: 975
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« Reply #4 on: January 12, 2010, 06:02:52 AM » |
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It was wide open desert near Mesquite, Nevada. Hard to imagine there was any issue with reception - in fact the Oregon claimed 5 bars for signal strength.
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Topic Name: GPS scrambling
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Reply #5 on: January 12, 2010, 07:01:36 AM
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bmike-vt
Location: Horgen, Switzerland
Posts: 1122
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« Reply #5 on: January 12, 2010, 07:01:36 AM » |
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How far from Tonopah test area? Wonder if they locally scramble when needed...
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Topic Name: GPS scrambling
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Reply #6 on: January 12, 2010, 08:07:16 AM
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dave54
Location: Lassen County, CA
Posts: 79
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« Reply #6 on: January 12, 2010, 08:07:16 AM » |
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GPS sometimes does get weird.
There is one spot in the Caribou Wilderness where the GPS places you on the antipode of the earth (Indian Ocean, from the Caribou Wilderness). Walk a few hundred yards in any direction and it is normal again.
The experts claim underground mineral deposits do not effect the signal. But I have seen too many strange things happen. I consider all just part of the adventure.
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Topic Name: GPS scrambling
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Reply #7 on: January 12, 2010, 03:06:29 PM
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stevage
Location: Melbourne, Australia
Posts: 174
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« Reply #7 on: January 12, 2010, 03:06:29 PM » |
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dave54: wonder if it's a hardware/software bug of some kind?
My oregon 550 has been extremely accurate so far, although once it was off by maybe 100m for maybe 20 minutes before suddenly snapping out of it. (Only noticed afterwards, when comparing a trace).
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Topic Name: GPS scrambling
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Reply #8 on: January 15, 2010, 11:04:19 AM
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dave54
Location: Lassen County, CA
Posts: 79
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« Reply #8 on: January 15, 2010, 11:04:19 AM » |
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No. Different units/different people get the same result. The really weird thing is it's intermittent, not consistent. No discernable time/day or weather pattern. A GPS expert was taken to the site. He said it is impossible for that to happen, but was stumped when it occurred during his visit. I blame it on the secret UFO base in nearby Lassen Peak!  As good an explanation as any. |
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Topic Name: GPS scrambling
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Reply #9 on: January 20, 2010, 07:02:07 AM
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AZTtripper
Moderator
Location: Tucson, AZ
Posts: 1732
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« Reply #9 on: January 20, 2010, 07:02:07 AM » |
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I had a similar experience the other day, went out to get a fresh track of some new trail here in Tucson came home to see the new track wasn't even close to where the trail really is. Funny!
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Topic Name: GPS scrambling
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Reply #10 on: January 20, 2010, 09:43:28 AM
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Pivvay
Riding and exploring
Location: Westminster, CO
Posts: 681
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« Reply #10 on: January 20, 2010, 09:43:28 AM » |
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I get weird behavior intermittently just leaving my house. Full multi satellite pickup upon rolling out, crazy readings for the first ~.25 mile then normal. No idea what causes it but it happens once in a while.
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-Chris Plesko
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Topic Name: GPS scrambling
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Reply #11 on: January 24, 2010, 02:00:00 AM
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Slowerthensnot
Have fun and go far
Location: Idledale, CO
Posts: 396
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« Reply #11 on: January 24, 2010, 02:00:00 AM » |
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I say vortex'es.... or maybe that just cuz i spent a week in sedona
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Topic Name: GPS scrambling
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Reply #12 on: January 25, 2010, 06:53:55 PM
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ScottM
bikepacking.net admin
Location: Wherever the GeoPro is parked.
Posts: 2863
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« Reply #12 on: January 25, 2010, 06:53:55 PM » |
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Yep, I've seen a few oddities like you describe Dave. They are pretty rare though, and usually short lived. Not sure about causes, but my guess is maintenance / adjustment of satellites as someone suggested.
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Topic Name: GPS scrambling
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Reply #13 on: January 25, 2010, 07:39:39 PM
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sean salach
Location: palmer, ak
Posts: 253
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« Reply #13 on: January 25, 2010, 07:39:39 PM » |
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I've experienced what could be nothing other than local scrambling when near a military installation(I used to live by one). Dave's Caribou Wilderness anomaly is obviously explained by the earth being flat, and that particular area being a sump where you 'technically' descend into the magnetic field of other side of the earth..... |
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