GPSr gone mad

[HOT TROT]

Went caching in the milwaukee area today. For about 8 hrs, we had no problems. We pulled into a park in Sussex, and lost our signals completely. We both had explorists along. We got out of the car and aquired signals within a minute or less. Got back into the car and lost our signals almost immediately and putting the GPSr into map mode, my cursor went SW at a speed of 550 mph until I turned it off. This series continued to occur. Every time we got out of the car we acquired a signal almost immediately. At about 730 pm we headed back to Madtown. Once we hit the I, our receivers acquired a signal inside the vehicle again. I drive a Pontiac Aztec if that helps. Any ideas?

[zuma]

Hi,

When my GPS starts actiing weird, I usually attribute it to the CIA or Defense Department messing with the satellites, but then I am just a little paranoid.

zuma

[knoffer]

The Sussex Triangle??? 😯

Very strange I was in Sussex and the surrounding area yesterday and had no problems receiving signals while in the car. Then again I have a Subaru Impreza and a Lowrance Expedition C so not really an Apple to Apple comparison.

Occasionally I lose all signal for no reason at all. I just turn the unit off and on and it immediately locks on and has no problems. Could be as Zuma suggests.

Did you check the skies?? Might have been an UFO. 🙄 😆

[Lostby7]

I was caching around Sussex, Lannon, Butler, West Bend, Germantown and Menomonee Falls and had no issues on Sat or Sunday….I even cleared up some previous DNF’s so the CIA and or UFOs were not problematic for me. I did however see a coyote…perhaps it was Wile E. Coyote, and he was messing with your GPS as he was goin after that crazy Road Runner? Granted I didn’t see any rockets, but you never know…

[Team Hemisphere Dancer]

Last summer I was showing someone how to cache. I was riding around in their vehicle and I could not get a signal. As soon as I opened the window and stuck out the GPS’r it locked on. Which kind of sucked because when I brought it into the car to look at it I lost it again.

Come to think of it it might have been a Pontiac too. Is this the beginning of the “Pontiac Effect?”

[HOT TROT]

While I have only had this vehicle for less than a month, I did previously have a pontiac. And yesterday the first eight hours of caching went off without a hitch. It seemed like it must have been something in the vehicle, but we have no idea what it could have been. I’m just hoping this doesn’t occur again.

[hogrod]

Solar flares are known to cause electronics to go buggy, though I’m not sure on the conditions yesterday. Any electronic device is vulnerable to changes in the Electromagnetic field around it. strong EMF be it caused by the sun, cellphone tower, electric lines, and even your gps.

current solar flare activity
http://www.n3kl.org/sun/status.html

I have not experienced any really strange issues with either of my garmin gpsr(legendC or 60cx), but did encounter speed issues and signal loss with both my magellan meridian gold’s. In fact one of my meridian golds would set off our FRS radios if it was within 8ft and the FRS was on the right channel.
I have seen people online with the garmin GPS V having these issues, so its definitely not just magellans that are effected.

[Jeremy]

This is a particular problem with the Aztek and other GM vehicles due to a coating/film placed on the windshield. Basically the film blocks or attenuates RF signals, including signals coming the GPS satellites making it tough or impossible to get a lock.

This is also big deal if you ever want to use an I-PASS device (RF transponder for dealing with the toll roads south of the border). From the I-PASS website:

@I-PASS website wrote:

According to experience thus far, standard Flatpack Transponders WILL NOT work on the following vehicles:

* Buick Roadmaster
* Oldsmobile Silhouette
* Pontiac Montana
* Pontiac Transport
* Cadillac Catera
* Mercedes S class
* New Mercedes E class
* New BMW 7 series
* New BMW 5 series

Flatpack Transponders DO work in a specific location on the following vehicles:

* Chevy Venture – halfway between the rear view mirror and passenger side window, mounted half in and half out of the film located on the windshield
* Buick Rendezvous / Pontiac Aztek – Drivers’ side next to the rear view mirror, half in and half out of the film located on the windshield

Maybe it is time to upgrade the Aztek (something more stylish perhaps :))? Or hold the GPS units next to the side windows (that probably aren’t coated) or use an external antenna mounted outside the vehicle.

[marc_54140]

Zuma and paranoid in the same post? Yah, that sounds right!

[AuntieNae]

Jeremy is correct.

Greenback, a Chicagoland geocacher, has a Pontiac Aztec. He uses an external antenna plus has a special I-Pass device in his front bumper.

AuntieNae

[HOT TROT]

I understand the windshield idea. I guess what I also don’t understand, is why in the 20+ hours I’ve had the GPSr turned on, there was just that window of 2-3 hours where it wouldn’t work. What other factor could magnify the effects?

[Cache_boppin_BunnyFuFu]

The summer of 2005, while up in the Crivitz area, I lost all satellites for 45 minutes and we were having a clear day and I was in an open field. When I got back home I told a co-worker about the situation and they said while out 4-wheeling up there the same weekend, the samething happened.

I guess it has to do with the position of the satellites in the sky and there are occasions when they orbit too low in the sky and we just can’t pick them up.

Where are the Mythbusters when you need them??

[Jeremy]

@Cache_boppin_BunnyFuFu wrote:

I guess it has to do with the position of the satellites in the sky and there are occasions when they orbit too low in the sky and we just can’t pick them up.

Where are the Mythbusters when you need them??

Anne, I didn’t know you were a scientist… you know about satellites, orbits, and other space stuff? 😀

Anyway, as she said, the weirdness was probably due to the randomness of the “constellation” of GPS satellites over your head. Given the windshield issue, you’d have more trouble with “low strength” satellites, those low on the horizon, than most folks. So if you happened to hit a time where there were few satellites visible and all these were low on the horizon, you might not be able to lock on the minimum number necessary for a position fix.

Here is a little online tool (with a really poor user interface) for predicting GPS satellite orbits and generating GPS signal quality charts.

CalSKY GPS Constellation Calculator

Here is an example quality chart for the next couple hours in Wisconsin:

Minimum Elevation of Satellites: 5 deg



Date     Time  Sats   PDOP   TDOP  SV0        1         2         3

h  m                      SV12345678901234567890123456789012

19 Mar  22:19   10   +2.59   1.31   >|    ||      X |   |  X |    XX

19 Mar  22:49   10   +2.25   0.93   >|    X|     XX X   |  | |     |

19 Mar  23:19   10   +2.09   0.91   >| X  X|     X  X   |  | |     |

19 Mar  23:49   10   *1.99   0.84   >| X   X     |  |   |  | X X   |

20 Mar  00:19   10   +2.17   0.90   >| |         |  |  |X  X | X   X

20 Mar  00:49    7    2.96   1.72   >  |         |  X  X   X | X

20 Mar  01:19    8    2.75   1.42   >  |    X    X  X  X   | | |

20 Mar  01:49    9    2.91   1.39   >  |    | X  |  X  |   X | X

20 Mar  02:19   10   +2.12   0.85   >  |    | X  |  X  |   X | X|

20 Mar  02:49    9    3.22   1.69   >  X    |  X |     |   | | XX

Note that 23:49 looks like an excellent time for caching with 10 sats in view and a PDOP under 2. Just an hour later, there will only be 7 sats in view and a high PDOP of 2.96.

So if you are really paranoid, you could check the GPS constellation forecast before heading out caching. And if you were flying a commercial airliner using GPS for navigation you’d HAVE to run a RAIM/FDE prediction similar to this ensure that you’d be able to track enough satellites during the entire flight to positively determine your position (a safety critical GPS usually requires 6 or more satellites in view).

[djwini]

i wasn’t out yesterday, but i was out today and kept losing the sats. the trees don’t have leaves on them and the sky was clearing, so who knows what was going on. i like the ufo idea.

[Averith]

Jeremy wrote:

This is a particular problem with the Aztek and other GM vehicles due to a coating/film placed on the windshield. Basically the film blocks or attenuates RF signals, including signals coming the GPS satellites making it tough or impossible to get a lock.

I have this problem with our Buick Rendezvous, unless I place the GPSr right next to the drivers side door on the dash I can not get any signals at all. Works fairly well as long as I place its mount there.

[Author]

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