Question

how do I display the user location in a mapView while not running GPS to update the location (at all)? Will

mapView.userTrackingMode = kCLLocationAccuracyNearestTenMeters;

do the job or will GPS still burn battery in the background?

Thanks 🙂

Answer 1

I’m going to attempt to answer your question as best as i can given the limited information.

The GPS has 3 main modes that go from low power to high power, low accuracy to high accuracy.

• Location Tracking off
• Background location updates (uses cell towers and wifi)
• GPS location updates

An MKMapView will show a blue dot for the user location if you set showsUserLocation to YES. The MKMapView will use all available location methods to find the users location as accurately as possible and keep updating it while this is set to YES.

The tracking in MKMapView, a mode which keeps the users location centred on screen, moves the visible map region as the user moves and is available in iOS5. you are given three MKUserTrackingModes to choose from. From the docs:

MKUserTrackingModeNone: The map does not follow the user location.

MKUserTrackingModeFollow: The map follows the user location.

MKUserTrackingModeFollowWithHeading: The map follows the user location
and rotates when the heading changes.

So setting it to kCLLocationAccuracyNearestTenMeters isn’t going to work as it is not an available option in this context.

Will showing the location burn battery in the background? It depends on what you mean by background. When the user taps the home button the MKMapView is forced to stop using the GPS by the system. While the app is running and the MKMapView is alive and has the showsUserLocation property set to YES it will keep using any available method, including the GPS, to update the location. You have a couple of strategies to reduce this.

1) presume that the user needs to see their location updated while the map is on screen. In which case keep showsUserLocation set to YES until the map is moved off screen, or the device is locked, then set it to NO

2) Presume the user only needs to see a static marker of their location from a particular point in time, like when the app is opened. In this case you need to make a CLLocationManager object, ask it to startUpdatingLocation, filter the delegate messages for the accuracy you want, and then turn off location updates (stopUpdatingLocation). You can then add an MKAnnotation to the MKMapView to show the user their location.

As you can see number 2 is more work, yet very power efficient. Number 1 is easy, but will use more battery while the map is visible. It is up to you to decide which behaviour the user expects and to implement your app accordingly.