Mylriahd

... or at least thats what my navi said this morning. We had a huge thunder / lightening storm here in the Seattle area last night (very rare actually), and I'm assuming it did something to the GPS system in the car.

Pics you say? I wish! I pulled over to get my cell phone out of the trunk so I could take pictures, only to find I had left it with my laptop at home. (I was only 2 minutes from home.) SO I turn around to get it, and by the time I get home the navi had managed to re-track to the correct road.

Thats good though, I was having nightmarish thoughts of having to take my car in and letting them rip up the dash to replace my navi system. Thankfully, that won't happen.

Is this something I can expect if I'm in an electrical storm like that? I'm new to GPS, but it seems reasonable; i'm just glad it was able to recalibrate itself.

rets

GPS is new to me, too... interested to know what's going on.

batting_cleanup

From what I have been reading in this forum your TL hydroplanes on water. I have had NAVI in two different cars and have not yet had the TL out in a thunderstorm. With the Lexus system and when I had DirecTV storms would take them both out temporarily. Signals don't travel through heavy cloud cover.

Mylriahd

That's whats interesting though. This morning on my way to work it was clear blue sky (another rarity for Seattle. ) The storm ended last night around 2am, and I left for work at 7:30. So it'd have to have been a residual thing. I'll probably never find out since I'd have to drive to the mid-west to experience anything like that again.

youngTL

I work with GPS all the time. At work we use expensive precision GPS accurate to about 10cm. But the important thing to remember is that you have to imagine the sky like a 3D map that looks like half of a sphere. If your GPS is in contact with 9 satellites, you are going to get a very accurate reading. If you only have 3 satellites, the reading will have more error. If it's constantly fluctuating, you get GPS "zingers" (if you were to plot a graph of your location), which show you jumping to a location very far away (dependign on the precision of the instrument used, and I doubt they use $12000 GPS equipment in the car, so its probably accurate to ~5m normally). Also, the nearer the satellites are to the horizon, the worse your positioning will be. The best configuration would be as many satellites as possible (realistically 5 or 6) in a circular pattern above you like the noon sun. Thunderstorms reduce the accuracy of the GPS by interfering with the signal. I'm guessing that you had a few horizon satellites with a bad signal, setting your position hundreds (or thousands!) of metres off. Any lakes within a couple km of you?

GaleForce

Today on my way home it had me driving like in some other town far, far away. It corrected after a few mins.

rets

Thanks... well info.

lindros2

Does anyone know the correction scheme which is used?

A couple of months ago I manually moved my location from downtown Atlanta to my real location (10-15 miles north at the time) and it was fine afterwards.

Sherlock

I had to correct once, but it was a matter of a few tens of feet, it didn't have me at intersections properly and I kept missing turns thinking it was the next block, not the one I was on.

And there are some "bread crumbs" on some lawns where it had me about 20 feet off the path, and thought I was driving thru yards and houses.

youngTL

I'm guessing it might be relaying to a base station somewhere in your area, and lost the relay, causing you to have an offset of a large distance (the distance from you to the base station). It surprises me that it doesn't correct this automatically, although I know with handheld GPS, if you are using a base station for a reference point, you have to calibrate it manually.

youngTL

Errors like that are very common. A bad satellite configuration will do that. If we assume the accuracy is about 5m, then it could fluctuate up to about 10m (5m in any direction). I'm guessing that this GPS system only measures your lat/long, and not the elevation (height above sea level/height above IRE).
IRE = International Reference Ellipsoid, a common sea level.

Mylriahd

Yeah, I DO live near a lake; but its to the west of me. I was driving north, and the map had me moving west.

I haven't looked in the manual yet (too busy at work doing this silly "job" thing.) Is there a way to calibrate the GPS? I too find I get "make a u-turn" messages when I'm at the light for the turn I was told to make.

Mylriahd

It does show elevation in the "current position" screen (though that doesn't necessarily mean that it actually uses that number in it's calculations now that I think about it.)

youngTL

I don't have the '04 TL so I couldn't tell you about the calibration. I know for sure that it doesn't calculate anything from the elevation data. It takes the x-y (or lat/long) data, and calculates the z (elevation) from that. GPS can get 'disoriented' sometimes if it loses ALL of the satellites. It should just tell you 'no signal' or something, but sometimes it thinks there is one and it's horribly wrong.

Sherlock

it could also have our elevation solely from data on the dvd maps. cuz from X and Y, it would know on the map data. Just another possibility

youngTL

That's almost what I said except in different wording.

Teh Jatt

this happened to me few times, I left my house and looked at navi and my car was going somwhere else, flying over the houses and then it corrected it self but now i see dots where the car was going, and thats where the houses are....... oh yeah my car flies over the houses

TLme

These types of errors are common to consumer GPS units. Usually a reset will correct it. Also, if you have the GPS turned off and travel a long distance, then turn it on, it can become confused until a good link is established. The Geocaching site has a good forum for GPS questions.

http://www.geocaching.com

youngTL

The confusion can last for several minutes too, assuming it's possible to get a reasonable signal.