[Hopka]

I'm sceptical. You can actually use the upper button on the left side of the app pictured in the article [1] to calibrate that app. So you could make it show whatever inaccuracies you wanted. And it's far from an "unfixable sensor problem" that "would put a dent in Apple's reputation". Also, analog bubble levels aren't always perfectly accurate either.

[1] https://itunes.apple.com/us/app/ihandy-level-free/id29985275...

[kalleboo]

According to users in the thread about this on macrumors, the error isn't linear, and if you calibrate it, you still get inaccurate readings once it's off-level.

  > The issue is that it cannot be calibrated out. I've tried, 
  > it can't be done. You can zero it in one orientation but then 
  > the error is doubled in the opposite orientation.

[MattBearman]

The relevant info from the link above:

* IMPORTANT MESSAGE. PLEASE READ *

Because the sensor inside every individual iPhone/iPod touch could be built slightly differently, to make the level more accurate for your device, you need to calibrate before use.

To calibrate:

1. Find a flat surface.

2. Hold your device upright (in portrait mode and home button at the bottom), put the bottom edge of the device on the flat surface, then press Calibrate button (the one with a target image on it) to calibrate the portrait mode.

3. Turn your device 90 degree clockwise (now it should be in landscape mode and home button on the left hand side), again keep it upright, and put the current bottom edge (long edge) on the flat surface, then press Calibrate button to calibrate the landscape mode.

4. Put the back of the device against the surface, then press Calibration button to calibrate the face-up mode

5. You are ready to go!

[arrrg]

Apple’s built-in compass (which has not calibration) also shows many devices to be off. I’m not sure why that person chose a third-party app to show this off.

This is a real issue.

[andyhmltn]

AFAIK you can calibrate the compass. At least in iOS7. But using an iPhone 5 I always find the compass to be incorrect most of the time.

[wklauss]

No to mention that it might not be an Apple problem, but an industry-wide problem. I've tried to replicate this on a brand new Sony Xperia Z1. It marks -2 degrees on a flat surface. Never occurred to me to test these things before.