Six iPhones tested, and they can't agree on magnetic north

Apple’s iPhone 5s is already getting bad press for bugs and errors, with recent complaints focusing on an unreliable gyroscope/accelerometer. Some outlets are speculating that the problem is tied to Apple’s decision to change the manufacturing source of its accelerometers for the 5s and 5c, but TechHive believes that the compass-accuracy problems extend beyond Apple’s two latest smartphones.

On Thursday we ran a series of tests and discovered that the Compass app in both iOS 6 and iOS 7 reported screwy results across a wide range of iPhones—from the iPhone 4 to the 5s and 5c. We recalibrated each phone multiple times, and often found that the results changed wildly from one test to the next.

The inconsistencies occurred in multiple locations around our office, and continued when we took our testing outside. Apple’s support docs warn that environmental factors can affect the phones’ digital compasses, which is why we tested the phones in several different locations and made sure to recalibrate each phone after moving it around or picking it up.

Left to right: the iPhone 5s, the iPhone 5, and the iPhone 5c. Click the photo for a close-up look at the inconsistent readings.

We first noticed that something was amiss while trying to replicate Gizmodo’s findings that the iPhone 5s has inferior sensors to the ones in the iPhone 5. Unlike Gizmodo, we didn’t see anything wrong with the leveling capabilities of the multiple iPhones we had lying around. We did, however, find that their sense of direction was completely unreliable, with readings across different phones disagreeing wildly. Worse yet, the problem persisted even after we recalibrated the phones eight different times.

Our methodology and results

To test the accuracy of the various phone compasses, we purchased a $15 Suunto A-10 recreation compass and took an armful of phones out in front of our office building, away from the electromagnetic interference within. Before testing each phone, we quit and restarted the Compass application, calibrating whenever possible. All the phones were set to report magnetic north as opposed to true north.

We ran the test at least three times on each phone, restarting the apps between trials and testing the phones one at a time, as we noticed that having other phones nearby affected the reading of the compasses.

We set the Suunto compass to north and placed it on top of a map of San Francisco. We used the map’s grid lines to line up the phones with the Suunto. We tested five types of phones: an iPhone 5s, an iPhone 5c, an iPhone 5, an iPhone 4s, and an LG G2. All of the iPhones except the 4s were running iOS 7 (the 4s was running iOS 6).

iPhone compassimage: Michael Homnick
Sometimes iPhones were close, and other times they were 20 degrees apart.

The iPhone 5s showed that it was pointing to 12 degrees when we lined it up with our Suunto compass set to 0 degrees—the accurate direction of magnetic north. Restarting the app and recalibrating the compass put the same iPhone 5s 22 degrees off from the Suunto. Restarting the app and calibrating a third time brought the iPhone 5s the closest yet, with a reading of 10 degrees off of our conventional compass. The iPhone 5c’s results were much more consistent, with readings of 12, 11, and 9 degrees, respectively. We took five readings with the iPhone 4s, and the results ranged between 9 and 19 degrees off of the Suunto, averaging about 14.5 degrees wrong.

We ran the test on three different iPhone 5 models, and found the worst deviation there. One model was not accurate at all—15 degrees away from 0 at best, and 28 degrees at worst. That’s pointing starkly northeast! Another iPhone 5 did very well, just 5 or 6 degrees from 0, while a third iPhone 5 fluctuated between a respectable 6 degrees away from north and a truly misleading 21 degrees away.

Just to give an Android phone a whirl, we replicated our tests with an LG G2 using Compass Pro from Gabenative, and found that the Android phone’s readings were the closest to our Suunto, merely 3 to 4 degrees off.

An inaccurate compass is a problem, but one that is sometimes accurate and sometimes inaccurate is just as bad. If your iPhone tells you that you’re heading east, you don’t want to worry about whether you happen to have a model that delivers consistent and accurate results. And if you recalibrate and get results that differ by 20 degrees, you don’t want to wonder whether your readings were right the first time.

Article updated to clear up ambiguities between true north and magnetic north.

Serenity Caldwell contributed to this report.

For comprehensive coverage of the Android ecosystem, visit Greenbot.com.

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