How does Field Maps use GPS on an iOS device?

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11-18-2021 12:25 PM
MatthewKing
Occasional Contributor II

Like the subject line...how does Field Maps use GPS on an iOS device? 

I'm asking b/c at a recent event we have three Trimble units and one iPad running tracker on Field Maps and the iPad had several tracks and Last Known Locations that were several miles from its actual location.  All of these errant tracks were when Activity (as listed in the table) was either stationary or unknown.  The Trimbles were spot on.

Does an iPad (or iPhone) use GPS but if it can't get a satellite signal for whatever reason resort to cell tower triangulation?  Besides pairing the iPad to a high-accuracy GPS receiver is there a way to restrict the iPad to just GPS?  This iPad is WiFi-Cellular so it has a GPS radio.

Thanks!

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3 Replies
ColinLawrence
Esri Regular Contributor

Hi @MatthewKing ,

 

You could try turning off Wifi on the iPad; its possible you are picking up errant locations from nearby wifi signals. 

Better yet we have recently added a setting in the profile settings in Field Maps to toggle "battery optimization" which is on by default. Try toggling this setting off and see if you get better results as this increases the frequency of location requests which should be restricted to the GPS. Keep it mind this may be more costly on terms of battery performance. I hope this helps!

 

Regards,

Colin

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MatthewKing
Occasional Contributor II

@ColinLawrence thanks for the response and suggestions.  We were out in the middle of the woods (but still had decent cell phone signal) so it's doubtful that it's a WIFI signal...unless someone had their phone hotspot on.  And battery optimization was already off, so who knows.

-Matt

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ColinLawrence
Esri Regular Contributor

@MatthewKing Ok thats good to know. If you mean literal woods it could be a case of inference in the GPS signal caused by tree cover. The trimble units should utilize more satellite satellite constellations and could therefore be less affected by this.

To more directly answer your original question -- we tap in to the iOS devices core location provider to get locations for tracks; whether this is coming from an external GPS, internal GPS, or other source, we are always looking in the same place. We can use the battery optimization setting to ensure we are always requesting locations instead of relying on on your activity detection at times, but this will not filter out "bad" locations from a GPS. 

I am curious if you still have some tracks with these bad locations on your device? We have a setting called Smart Rendering in the Track Display options (Layers tool > Options under My Tracks > Smart Rendering). Its On by default meaning low quality points would be filtered from the Map view. This wont stop these locations from being recorded but it may give you a better idea of when/where this is happening. 

 

Regards,

Colin

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