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I'd like to develop an iPhone 4 app that uses the compass API, but I need readings at least as precise as a half a degree (eg. 100.5).

What kind of precision does the compass API provide?

Chad Johnson
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    FYI, there's a difference between [accuracy and precision](http://en.wikipedia.org/wiki/Accuracy_and_precision) that might be worth knowing if you are going to do further research on the matter. – Aidan Steele May 11 '11 at 22:15

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In my experience, not anywhere near that.

LaC
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According to this site, the accuracy is supposed to be within 1.4 degrees. As with any magnetic compass, interference from surrounding objects and electronics will have some impact as well.

Joe Stefanelli
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You have to tilt compensate the compass first, so the accurary of accelerometer matters too.

After a sophisticated calibration of both the compass and the accelerometer, it is nowhere near that on the Shimmer2r platform.

I would expect the iPhone compass to be worse, especially without calibration.

Ali
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You can use de Giroscope + Compass to get a bigger precision.

saimonx
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