Core Location skips user movements with CLVisit monitoring turned on

Question

The app I'm working on records information about places where user spends most of his/her time. Core Location's Visits monitoring fulfil all it's requirements in location information absolutely.

While testing this app our QA-engineers revealed evidence that Core Location misses Visits for unknown reason. And this is not a result of low location accuracy. Core Location starts skipping locations registered before without any problems.

To make things clear we've run the test. I installed on his phone our app and example app: https://github.com/steveschauer/TestCLVisit

After 3 days of testing we compared locations from our app, sample app and information from Settings->Privacy->Location Services->System Services->Frequent Locations.

Information from all sources was equal. So we can say that it's not an issue of our app.

But while all locations registered at first day was correct, many locations of second and third day were missed. Only few of them were registered.

Is it normal behaviour for Visits Monitoring? What could be a reason of such skips? Does anybody have negative or positive experience of Visits monitoring?

Answer 1

Yes, I faced some similar issues while using CLVisit API. There is also an article from NSHipster, which describe some issues with CLVists and these are still present in iOS 10. It essentially goes on to say that if you want infrastructure that extremely precise don't use CLVisit. From our experience, CLVisit is not all that precise. While start and end times are generally accurate within a minute or two, lines get blurred at the edges of what is and what is not a visit. Ducking into a corner coffee shop for a minute might not trigger a visit, but waiting at a particularly long traffic light might.