iOS geolocation watchPosition Incorrect

[himanchau]

Description

Watch location of user on iOS seems to not be using GPS. The accuracy never goes below 65 and the speed is negative, which seems like that the GPS is not kicking in. It works just fine for Android. Also, navigator.geolocation works just fine in the browser with accurate speed and accuracy. (https://codepen.io/himanshu/full/bqoEQN/)

Reproduction

Reproduced in Expo. (https://sketch.expo.io/S15lAdDsx)

Solution

React native needs to respect the enableHighAccuracy and distanceFilter flags and return the proper accurate location.

Additional Information

• React Native version: 0.42
• Platform: iOS
• Operating System: Mac & Test on Device
• Dev tools: xCode

[mbokowy]

I've the same problem. How to fix it?

[jcharlet]

Hi,
same issue, get negative value for speed and weird coordinates/timestamp. very critical to me since I started implementing an app which works fine on android and am porting it to ios now (to deliver in may).

any workaround ? any visibility on a fix ? are we supposed to vote this up on some other platform than github?

"react": "15.4.2",
"react-native": "0.42.3",
 platform ios 10.3
 tested on ipad 2 (target is iphone but this is all I have at the moment)

thx,
Jeremie

[jcharlet]

hi @himanshu266 @mbokowy did you guys find a workaround?

[himanchau]

@jcharlet Yes, I changed this default value to 0. This works for me because I wanted constant updates. You may have a different case.

https://github.com/facebook/react-native/blob/master/Libraries/Geolocation/RCTLocationObserver.m#L28

[plougsgaard]

@himanshu266 Let me know if I understand you correctly - you hardcoded the RCT_DEFAULT_LOCATION_ACCURACY value to 0.0 inside the RCTLocationObserver.m file? And this prevents iOS from just using the network location?

[himanchau]

As the name describes, it's the location accuracy. When you set it to 0, every single time the phone moves, even a bit, new location gets updated. Otherwise it was set to 100 meters, which is pretty big gap.

[plougsgaard]

@himanshu266 True, though that should be possible to do with the distanceFilter prop too, right? For me the issue isn't that it doesn't update often, it's just that it's very inaccurate because it doesn't seem to use the actual GPS (not an issue on Android).

[himanchau]

Yes, the distanceFilter should work, but if you look lower down in the file you will notice they are doing the math and resetting it back to the default. Hence my fast easy fix for my application was to set the default to 0.

[plougsgaard]

I'll try that then, thanks for explaining.

[jcharlet]

sorry to ask such a trivial question (am new to the node/xcode world): how do you patch a file from a node_modules package ?

@himanshu266 Do I have to replace the value directly in that ./myApp/node_modules/react-native/Libraries/Geolocation/RCTLocationObserver.m (while node_modules is ignored by git and overridden at any npm install). Is there a cleaner way so that it's not in node_modules and in my git codebase?

I cannot monkey patch since it's not a js file..

[plougsgaard]

@jcharlet I can confirm that changing the value in the library under node_modules does work!

I think the only real solution is to actually fix the underlying bug in react-native itself 🙂

[jcharlet]

thx @plougsgaard !

[mellikestocode]

Any solution towards improving the accuracy/speed/heading that returns from the geolocation api?

[clementcontet]

@himanshu266 thanks for the fix.
But I would rather set RCT_DEFAULT_LOCATION_ACCURACY to kCLLocationAccuracyBest instead of 0.0 because the value of these "accuracy constants" are not documented by Apple and may change (if kCLLocationAccuracyBest is 0.0, what is
kCLLocationAccuracyBestForNavigation?)

Back to the root cause, I don't get why this desiredAccuracy is changed after we succeed or fail to get a position?

See:

• https://github.com/facebook/react-native/blob/master/Libraries/Geolocation/RCTLocationObserver.m#L312&L316
• https://github.com/facebook/react-native/blob/master/Libraries/Geolocation/RCTLocationObserver.m#L348&L352

And why compare the difference ABS(_locationManager.desiredAccuracy - RCT_DEFAULT_LOCATION_ACCURACY) to 0.000001?? (again, we have no idea how Apple implemented their accuracy constants)