Geolocation API automatically reverts to 100m accuracy on iOS

[rburgst]

The current implementation of the geolocation API always reverts back to an accuracy of 100m after receiving the first location update.

• Code snippet

https://facebook.github.io/react-native/docs/geolocation.html

componentDidMount() {
    this.startGpsWatch();
}

startGpsWatch() {
    let geoOptions :GeoOptions = {
        enableHighAccuracy: true,
        distanceFilter: 3,
        timeout: 20000,
        maximumAge: 4000,
        accuracy: 1,
    };
    this.watchID = navigator.geolocation.watchPosition(
        this.onLastPositionReceived.bind(this),
        this.onLastPositionError.bind(this),
        geoOptions
    );

onLastPositionReceived(position) {
    console.info("accuracy", position.accuracy);
}

• What's the version of React Native you're using?

latest 0.26.1

• Does this occur on iOS, Android or both?

only on iOS

• Are you using Mac, Linux or Windows?

Mac

The issue seems to stem from this code

react-native/Libraries/Geolocation/RCTLocationObserver.m

Line 337 in 2310494

if (ABS(_locationManager.desiredAccuracy - RCT_DEFAULT_LOCATION_ACCURACY) > 0.000001) {

- (void)locationManager:(CLLocationManager *)manager
   didUpdateLocations:(NSArray<CLLocation *> *)locations
{
   ...

// Reset location accuracy if desiredAccuracy is changed.
// Otherwise update accuracy will force triggering didUpdateLocations, watchPosition would keeping receiving location updates, even there's no location changes.
if (ABS(_locationManager.desiredAccuracy - RCT_DEFAULT_LOCATION_ACCURACY) > 0.000001) {
    _locationManager.desiredAccuracy = RCT_DEFAULT_LOCATION_ACCURACY;
}

Where RCT_DEFAULT_LOCATION_ACCURACY is 100m.

The rationale for this code is somewhat unclear to me. The comment does not seem to fit to the implementation.

[lacker]

The code you are linking to is inside didFailWithError so it looks like the accuracy is only resetting on an error. My suspicion is that in your project it is actually erroring a lot for some reason which is causing those resets. I'm going to close this issue since it's been a while but if this theory is incorrect feel free to reopen.

[rburgst]

In my tests this was happening quite frequently therefore ruining the functionality. IMHO the code should still revert to the previously set desiredAccuary.

[rburgst]

In addition the same code can be found in https://github.com/facebook/react-native/blob/master/Libraries/Geolocation/RCTLocationObserver.m#L269

- (void)locationManager:(CLLocationManager *)manager
     didUpdateLocations:(NSArray<CLLocation *> *)locations

[leokaessner]

@rburgst Did you find a solution? We still struggle with that problem. As the constant is defined as makro, we even can't really subclass or categorize the RCTLocationObserver.

[rburgst]

I did modify the react native code. As I have it checked in I always put it back when upgrading. On 01.06.2017 at 14:40, Leo Käßner <notifications@github.com> wrote: @rburgst <https://github.com/rburgst> Did you find a solution? We still struggle with that problem. As the constant is defined as makro, we even can't really subclass or categorize the RCTLocationObserver. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#7680 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABZuy0mhOjca7YzGThqOS2bpNoPcQ1mks5r_rE6gaJpZM4IkEMH> .