If you are experiencing loss of the GPS signals it may be due to jamming.

GPS and Cell Phone jamming devices are turning up everywhere.

Use of these devices is prohibited by Federal Law. The fines are large and there is an active surveillance campaign to identify offenders.

http://www.gps.gov/spectrum/

http://www.gps.gov/spectrum/jamming/

http://www.gps.gov/multimedia/presen.../2012/03/WSTS/

When the Nav System in our cars looses the GPS signals it reverts to Dead Reckoning navigation. During DR navigation the calibration of the compass and distance measurement from the wheels becomes important. Compass calibration and wheel size calibration are addressed in the owners manual, however it looks like the technical writer sort of ran out of information on that subject.

 

Thanks for the heads up on this! I have never had the issue, but now that i have my IVIC Android emulation for my Android, I never use the stock nav system anymore. I use the WAZE and Google Navigation apps through my oem screen..always updated, more features and just flat out BETTER than Lexus NAV

 

This has exactly the same impact to the phone GPS as the car GPS except that the phone is unable to DR navigate.