I have been having trouble with my navigation system. At times it can not tell which way is North and at times is about 100 yards off. Today during two hour drive even my dash compass was off. I was heading East and it said I was heading North. Finally figured it out. My "smart" phone sitting on top of the dash seems to be the problem. Shortly after removing the phone from the dash everything went back to normal. Will keep an eye on this solution to be sure this is what it the cause. Hopefully this will be helpful to someone else.