Took my grandson camping this weekend. It was a new place, unfamiliar with the layout, and so after he crashed I sat out on the truck looking at what stars I could see through the trees. There was no moon up yet, and the only easy constellation I could see from my vantage point was Cassiopeia , due to the Big Dipper lying low on the horizon this time of year, and so I pulled out the cell phone to check the compass heading. The compass that comes standard on the iPhone had N in what seemed to me to be a funny direction, so I switched over to the GPS app and sure enough they were off 90 degrees from each other. After a few switches back and forth the basic phone compass moved to agree with the GPS compass, but then a little later the GPS compass had moved N to about where the standard compass first had it. Sunrise confirmed that the standard compass was off by 90 degrees the initial reading, and therefore the GPS compass was off at the point it gave a similar reading, though the GPS one was correct the first reading done with it. The moral of the story is that I am getting a real magnetic compass.