Nav System does not recognize location prior to 6 am

[Sherpa269]

For the last two weeks my nav system has failed to recognize my location prior to 6 am. When I leave my garage @ 5:30 am, the Nav system recoginzes my location (home). But when I start moving, the Nav system shows me moving in different directions that what I am actually driving. By the time I get to my destination, the nav system has me clear across the township, generally floating in a lake. Generally system is fully funtional when I leave they gym @ 7 am. There have been two instances when it has not. But the Nav system is always correct when I go to work @ 7:30 am.Does anyone have any ideas?

[tnpartsguy]

I'd contact GM about it, but here's my guesses, (and I hope there is a prize); the satellites are either out of range, or down for their maintenance cycle.

[ragingfish]

Have you ever left after 6 am and not had problems? Could it just be that the location of your home is the problem (perhaps the nav antenna is flaky)?

[northvibe]

if the nav works from your house at other times through out the day, then at that time in the morning the satallites are prolly not really covering your area enough. i forgot how many it needs to get a good reading...3 or more...something like that.

[Mr. Poopypants]

I would think satellite position has something to do with it. Unless you are, in fact, driving to the middle of a lake, if that's the case, I would say it's working like a champ.

[Sherpa269]

I think we have a winner. I think you are correct that it is an issue satellite. In the upper left hand corner of the screen there is the arrow pointing north, and below it there is usually a blue "GPS" bar. When I am experiencing this problem, the blue bar is not there.When the blue bar comes back, the problem seems to be corrected.Just another geographic anomaly of this hole we call Michigan.Sorry, some woman in Oregon claimed the prize.

[Toolman]

Sounds like the blue bar is signal strengh. On my handheld it goes wacko when the signal is marginal. If there is no signal it goes nowhere, if signal is weak then it is just shows the wrong position.

[mcgusto82]

you have lazy GPS. take the snooze and turn it off. make that ******* wake up!!!!lolthere really isn't a way to fix this. maybe a A/M gps might work.

[northvibe]

launch ur own satellite that will circle michigan at like 5:30

[Jahntassa]

The Blue 'GPS' means it has a GPS lock, and it's doing positioning according to the satellite signals.Otherwise it's dead reckoning, using the speed sensor in the car, and the gyroscope in the unit to determine where you are. Both these systems should lead to a pretty accurate placement. It sounds to me like your unit is having fairly serious issues. I've never had problems with my unit using only dead reckoning (no gps). It could be something due to the cold, perhaps a bad soldier joint.If you still have any form of a warranty, i'd take it in and have it looked at. There is also a 'diagnostic' in the unit where you can see if it's recieving any signal off the sensors/satellites.

[esjones]

Possibilities - Bad GPS antenna or connection to the head unit. Something blocking the satellite signal (do you have anything laying on the top of the instrument panel?)It is most certainly NOT a satellite problem, nor an issue with not having enough satellites in the sky where you live. The signals are there... too many aircraft and other users depend on them. The problem is in your car.

[mcgusto82]

Quote, originally posted by Jahntassa »The Blue 'GPS' means it has a GPS lock, and it's doing positioning according to the satellite signals.Otherwise it's dead reckoning, using the speed sensor in the car, and the gyroscope in the unit to determine where you are. Both these systems should lead to a pretty accurate placement. ..being that this is true. the stock nav uses other inputs for accuracy and back up. your nav seems to be misbehaving.a trip to the dealer might be in order.

[Sherpa269]

@#$*)(@#$ Crap. My warranty expired about 2500 miles ago. I do have a radar dector clinging to the window, low, on the driver's side of the windshield, but that has been in the same general area for almost a year. Where is the GPS antenna?

[northvibe]

dont public gps use different satellites? because i have a garmin and that needs like 3 to work and only a couple times when i was toying with it it didnt have 3, but after a little bit it found some more.

[GMJAP]

Quote, originally posted by northvibe »dont public gps use different satellites? because i have a garmin and that needs like 3 to work and only a couple times when i was toying with it it didnt have 3, but after a little bit it found some more.They use the same satellites, I think, but the signal for public GPS is slightly "scrambled" so it isn't as accurate. Used to be much less accurate, but around the late 1990s they allowed the public signals to get better accuracy.

[binary]

GPS is simply a time code sent from a satellite with an ID attached. Each satellite has an atomic clock onboard. The GPS uses the signal from 3 or more satellites to calculate where it is based on how long it took time codes to get from various satellites - it's preprogramed with satellite IDs and locations. Our datacenter uses GPS timecodes for a two redundant time servers (NTP) - they're always accurate.Military GPS is more accurate because it does more precise calculations. Same birds - more math. There used to be a federal limit on how accurate civilian GPS could be, but thats not the case anymore.It can take a GPS system 0-15 minutes to get an accurate possition based on a cold start. Sometimes solar activity can cause problems - but that last few days have been very quiet.If I were to guess, I'd say the environment on your drive is interupting the process of your GPS getting a good range of satellite signals and takes a while to get up to speed. Or a fragged antenna... does it ever give an accurate signal?

[Toolman]

Spent a lot of time in the desert in Iraq, learned a few things about GPS. Some time before OIF they released the secure GPS sattelites to public use so that GI's with civilian GPS would be able to be as accurate as the military GPS. I also learned that my 150$ Magellan was MORE accurate than the 1200$ piece of crap that the miltiary uses, and was 5x smaller. Binary, seems you know your GPS pretty well. Are you Military, or where you?

[Sherpa269]

Quote, originally posted by binary »does it ever give an accurate signal?Yes it does. After my first trip in the AM, it works fine and dandy.

[Jahntassa]

Antenna is dead center in the dash, about 1 inch below the top, just on the inside of the defroster vent.Radar detector shouldn't interfere with it, and it wouldn't make sense that it would only interfere at certain times...And yes, they always used the same satellites. They just had a thing running called, I believe, Selected Availability. The military has control over how accurate the timecodes from the satellites are to generic GPS recievers. Military recievers would be uneffected.Also, you need at least three signals to get a position fix, four to get altitude, and more than that just adds to accuracy.It might be a cold soldier joint somewhere in line with the antenna?

[scott_h]

Stop getting up so @#$ early!

[binary]

Quote, originally posted by Toolman »Spent a lot of time in the desert in Iraq, learned a few things about GPS. Some time before OIF they released the secure GPS sattelites to public use so that GI's with civilian GPS would be able to be as accurate as the military GPS. I also learned that my 150$ Magellan was MORE accurate than the 1200$ piece of crap that the miltiary uses, and was 5x smaller. Binary, seems you know your GPS pretty well. Are you Military, or where you?Nope, never paid by uncle sam... but I read a lot and keep tabs on the tech out there. GPS had always facinated me, and now I maintain a couple of time servers that link up to them, so it's good to know the details.I've also read too many stories of soldiers writing home for civ-tech devices to replace their military issued. It's a sad picture of today's military...