I was curious about how the iPhone 3G S's compass feature work. After looking at Apple's patents and hardware discussion, I found the answer. The solution is actually quite simple. For a copy, email me.
http://www.macnn.com/blogs/2009/06/11/apples-iphone-emergency-mode-processor-features-patent.html</li></li></ul><li>Spectrograph Analysis<br />Once introduced, magnetic interference drops signal strength parabolically. Frequency and power ranges are consistent with GSM bands.<br />
Electronic Solution <br />Apple must be utilizing simple RF to determine North.<br />
Hardware Details<br />The AK8973 chip on the iPhone is a small sensor that “listens” for an ultra low frequency signal. <br />If that signal comes from a specific spot like North, paired with the accelerometer the device can calculate its orientation and direction.<br />Sources:<br /><ul><li>http://www.appleinsider.com/articles/09/06/24/cost_to_build_apples_new_iphone_3g_s_estimated_at_179.html
John W. Jewett, Raymond A. Serway,Physics for Scientists and Engineers with Modern Physics, pp 532-545, Brooks/Cole, 2007</li></ul> <br />
Possible Flaw: How does Apple transmit an RF signal around the world? <br />
Obvious Answer<br />Apple has built a Dharma station on the North Pole to transmit a signal!<br />
Contact<br />firstname.lastname@example.org<br />Twitter: @arseny<br />Oh, and check out FileMagnet, which really does use magnets:<br />