Since the iPhone 5S first started landing in the hands of excited new users a few weeks ago, there have been reports that the iPhone internal sensors haven't quite been up to snuff. We've confirmed the new iPhone's failings on our own, and they're embarrassingly off— they're so different from reality, that we're wondering how Cupertino let this phone out the door.

We tested two units of the iPhone 5S running the latest version of iOS 7 against the iPhone 5 as well as against real-world measuring tools to find out if the new iPhone's sensors are off, and if they are, how far off they actual are. In most cases, we used the iPhone's built-in iOS 7 apps for measurements, working under the assumption that Apple would properly calibrate its hardware to work with the software of its own design.



In the Gif and still image above, you see a pretty dramatic illustration of the difference between the iPhone 5S's internal inclinometer readings and reality. A simple Stanley spirit level tells the whole truth: The iPhone 5S's level readout in the iOS 7 compass software read 2-3 degrees off—other users are reporting that the level is off by as many as 4-6 degrees. And it's not just an iOS 7 problem because when we performed the same test with an iPhone 5, the readout was almost perfect.


We also tested the level using the free iHandy Level app to similar results. In all cases, we were sure to keep the side of the iPhone totally flush to the level.

Two-degrees might not seem like much, but it's actually a big deal: if you use this level to set up shelves they'd be obviously way off. Books would fall over, and guests to your house would think you're a dolt. In day-to-day phone usage, two degrees seriously screws with gaming. We fired up X-Plane, the flight simulator standard across platforms, and I found it more difficult than usual to keep my flight path steady and straight.



As with the simple inclinometer measurements, the iPhone 5S' gyroscope readings show a discrepancy between the iPhone 5 and iPhone 5S. Here's what it looks like when I tossed both phones on a level table. The iPhone 5 reads level, while the iPhone 5S reads -3. Again, you can expect this to screw up gaming as well as readings on motion based exercise apps, which are much of what Apple's new iPhone's new M7 processor is all about (more on the hardware implications below).



We did a brief test on the new iPhone's accelerometer data, and preliminary results seem to indicate that the 5S is registering way more latent motion than the iPhone 5. The above images show the readouts from the accelerometers of both phones sitting flat on a level desk. Our testing isn't conclusive, and it's only worth noting because the differences between the two handsets lines up with what we've seen from the iPhone's other sensors.

What's going on?

More likely than not these discrepancies stem from a calibration issue in the iPhone's firmware. Indeed, it's of interest that so many new handsets have issues but that the issue isn't consistent across devices. The reason that the iPhone's compass and gyroscope have us do a little calibration ritual every so often is because no two pieces of hardware are 100 percent identical. The solution to the current sensor woes, then, could be as simple as a firmware fix for the calibration.


That Apple hasn't pushed a fix for the issue yet suggests that it might be harder than a simple patch, especially, if it involves the new M7 motion coprocessor whose job it is to handle data from the gyroscope, compass, and accelerometer. If it turns out that the M7 is acting up, iPhone 5S owners could be waiting a long, long time before Apple makes it right.