GPS Must Have Coffee - GreenHybrid

wcmack · #1 (**permalink**) 09-28-2006, 01:00 PM

I left at 7 am for a breakfast meeting this morning, and followed a route I had taken several times before. On each prior occasion, the GPS display showed my position flawlessly.

This morning though, it seemed, well, sort of sleepy. It started showing my position several hundred feet behind my actual position. Then, in a few seconds, it lost its way altogether. As I negotiated a left curve on the road, the display showed the vehicle continuing to go straight and put me in the weeds several tens of feet off the road I was clearly still on! I pressed the "Map" button at lower left and this seemed to bring it to its senses. The display came up correct, and has been fine the rest of the day (I used it to guide me to a client's location today, and it worked spot-on).

Has anyone experienced the same or a similar thing? What could cause this behavior? I believe that the GPS transceiver has to be in touch with at least 3 satellites to calculate position. Could it be that it lost contact momentarily (the weather was good, and I have not seen it do this in the same location on prior trips along this route)? If so, shouldn't the unit show an error message?

Any experience from others would be helpful. Thanks in advance.

schmidtj · #2 (**permalink**) 09-28-2006, 01:28 PM

I've been in more rural areas and the location indicator has drifted off the road. BUT it sounds like yours was not detecting turns etc.
The Camry's GPS has a "dead reckoning" ability. A pizeo-electric (tuning fork like) directional sensor, and it also is aware of distance traveled (it counts wheel revoltions). Using these two inputs it can compute a darn good ground track even without a GPS signal. It's most used in indoor garages or forested areas. It also works when you first turn on the car until it aquires the necessary satellites.
If your's is not doing a reasonable job of "dead reckoning" combined with an area of poor map coverage, that might be your issue.
J

wcmack · #3 (**permalink**) 09-28-2006, 02:47 PM

J,

Makes sense to me. I'll keep a weather eye on it for the next few days to see if it happens again. Thanks for the input!