Roughly a week ago Yelp offered an interesting post on its blog. The post reveals how Yelp prevents false check-ins or “check-in fraud.” But more importantly it’s about how Yelp matches reported user location with business locations. It’s also a comparison of positioning methods and a discussion of their relative accuracy.
Yelp explains the three ways to locate a mobile device: GPS, cell tower triangulation and/or Wi-Fi positioning. Yelp then compares the accuracy of the systems and the devices that use them: iPhone vs. Android vs. iPod Touch.
Both the iPhone and Android handsets are able to use a hybrid system to locate users: GPS + cell triangulation + Wi-Fi. The iPod Touch doesn’t contain a GPS chip and is not a phone. So it only uses WiFi triangulation. Accordingly Yelp compares the accuracy of WiFi-only positioning vs. hybrid positioning.
Both Apple and Google do their own “in-house” location positioning. Both companies originally used Skyhook Wireless to do this but later developed their own systems. (As an aside, Google and Skyhook are currently in litigation about several issues tied to Google’s methodology and its relationship to the company. There’s also a way that Google’s “Wi-Spy” controversy is indirectly tied into all this too — but that’s a separate discussion.)
Back to the accuracy question: Yelp says that WiFi positioning by itself (used on the iPod Touch) was much less accurate than was the hybrid approach used by iPhones and Android handsets. And between the two it found that the iPhone was more accurate than Androids; however Android handsets typically did a better job of reporting potential location inaccuracy:
Phones consistently have the most accurate positioning, with a fairly small accuracy radius. Android phones are often inaccurate, but reliably reported that inaccuracy. And finally, iPods using Wi-Fi positioning proved the least accurate and usually reported incorrect accuracy radii.
According to Yelp’s analysis just under 60 percent of iPhone check-ins were less than a .1 mile (one-tenth of a mile) from the designated business location. That was true for only 40 percent Android devices by comparison. But because Android devices do a good job reporting the margin of location error, Yelp is able to compensate.
I’m not sure whether Yelp is objectively reporting the limits of location positioning for all iPhone and Android devices or more “subjecitvely” how its app interacts with these devices and location. I’m assuming it’s the former.
At roughly one mile out, Yelp said that 90 percent of iPhones and Android devices are accurate. This is going to be sufficient for most mobile use cases. However it’s potentially problematic for the “around me” or “near me” scenarios. And it also suggests the potential limits of so-called “hyper-local” ad targeting today.