GPS vs. Smartphone Accuracy Test

We test the accuracy of GPS units and smartphone apps for recording distances and elevation gain/loss.

Two years ago, there was a discussion on the Singletracks forums about whether smartphone GPS apps were as accurate as dedicated GPS devices from companies like Garmin. So we decided to set up a test and see for ourselves.

To test for accuracy, we would need a controlled course of known length and elevation. A local quarter mile running track offered the perfect place to conduct our test. Our first batch of GPS devices and smartphone apps included two iPhones, an Android tablet, a Windows phone, 3 GPS units, two GPS watches, and a GPS-enabled helmet camera. We strapped all ten devices onto a mountain bike and rode 10 laps around the track.

All but one of the devices reported distances within 3% of the actual length of the test course, and all but one device over-reported the distance. The iPhone and Android tablet running Strava were the most accurate in this test, followed by the Garmin Forerunner wristwatch and the Magellan Cyclo 505. Not surprisingly, the Garmin VIRB helmet camera came in near the back of the pack, along with an older GPS device meant for hiking.

If you like to create maps based on GPS data collected during your adventures, it’s important that the GPS tracks generated by your device match up with the actual route you travel. As you can see from the various maps we generated during our test, some devices--like the Nokia Lumina smartphone--produce tighter tracks than others like the iPhone or our hiking GPS.

In addition to testing distance accuracy, we also wanted to know how well each device tracks elevation, particularly elevation gain and loss during a ride. Since we tested on a flat running track, we expected the most accurate devices to report close to zero overall elevation change. Once again, the Strava app on iPhone and the Android tablet reported the narrowest elevation change, followed by the Garmin Edge 500 and Magellan Cyclo 505. The worst device at tracking elevation change in our test, the Garmin Fenix2, reported over 100 feet of elevation change along the flat track, despite featuring a barometric altimeter for improved elevation accuracy.

After our first round of testing, a few readers suggested adding a cyclocomputer to the mix to use as a baseline for our results. We chose a simple Cateye Velo 7 which measures the number of revolutions the front wheel makes to calculate speed and distance. We calibrated the Cateye Velo 7 by running a piece of tape along the circumference of the front wheel, then measuring the tape.

This time around, we ran 3, 1-mile tests to track not only accuracy but also consistency. Even though we used a fresh crop of GPS units and smartphones, the results from this test were similar to those from our first test. The smartphones, running Strava and Endomondo apps, were the most accurate, and all devices were within 3% of the actual course distance. Not only that, all of the dedicated GPS units were completely consistent from test to test. Our cyclocomputer didn’t fare well in terms of accuracy, but we chalk that up to calibration issues rather than a fundamental issue with the way the unit works.

The smartphones, along with the Garmin Edge 520, reported the least amount of elevation change along our flat course. Keep in mind, however, that smartphone apps generally do not report raw GPS data; instead, they process GPS data in the cloud to improve accuracy.

As you can see from our test results, there is no such thing as perfect accuracy when it comes to GPS devices or smartphones, though some are slightly more accurate than others, at least within a controlled test environment. So, as always, take your activity data with a grain of salt and realize that it will never be 100% accurate, no matter which device you use.

Read more online:
https://tinyurl.com/GPSAccuracyTest

Products from this video:
Garmin Edge 520: https://tinyurl.com/Garmin-Edge-520 (Affiliate Link)
Lezyne Mini GPS (similar model): https://tinyurl.com/Lezyne-Mini-GPS (Affiliate Link)
Bryton Rider 320 (similar model): https://tinyurl.com/Bryton-Ryder-320 (Affiliate Link)

Find more gear reviews on Singletracks:
https://tinyurl.com/Singletracks-Gear

Follow us:
On the Web: http://www.singletracks.com
Facebook:   / singletracksmtb  
Instagram:   / singletracks  
Twitter:   / singletrackscom  


Get Merch:
https://shop.singletracks.com/