How does the geofence work?

How, exactly, does the geofence decide whether I’m present or not? Does it look for my phone to actually cross the fence, or is it just looking to see if my phone is present within the fence? I’m trying to test presence with my phones, but turning them completely off doesn’t seem to trigger anything, which seems to indicate that crossing the fence is the key, not just presence within the fence.

Unless, of course, it’s unreliable as others have observed…

The geofence is actually a function of the phone… the app gives the phone the fence boundary, then the phone tells the smart things app when it when it crossed the boundary. ST does not look for the phone location, it’s the other way around - the phone tells ST when it’s inside or outside the fence.

Also, every time you open the ST app, it will check the phone’s current location (by asking the phone where it is) and update your presence state depending on whether you are inside or outside the fence.

As far as I know, there’s no way to have your phone “fake” leaving or arriving.

Ah, thanks, Steve.

You can have your phone trigger a “fake” leaving event if you edit your geofence to move it away from the house. You can edit that in the SmartThings mobile app by clicking the three lines next to “Dashboard” in the upper left corner, then clicking the gear icon next to Home.

But sadly, yes, the presence indication for my wife’s phone is sporadic. She left about 25 minutes ago but it still thinks she’s present. A couple days ago she was gone all day and it never registered her as away or returning.

Hi, I use IFTTT’s IOS Location function (Blue icon with white compass arrow). It sets up in the same manner as geofence, but seems more reliable and responds faster to your leaving and entering an area. You can set up different areas for entering and leaving if you like giving you more flexibility in how it reacts to your entering and leaving. Example: Real tight for leaving so that locks react quicker and larger for entering to allow a little more time for lights and locks to react to your entering. Like all web dependent devices it is not 110% reliable, but has proven more consistent than geofence. It would have to be set up separately for you and your wife on each of your phones. Good Luck!

PS. The IFTTT solution is great for triggering switches, but will not take the place of the presence function in Smartthings that is set by geofence. I have experienced delays in it updating my presence or lack there off.


The geo fence was explained to me in a different manner. The explanation I received stated that the triggering occurred as part of the service provider’s location services and that it notified (continuously?) the ST server as to my location and the ST server then determined if I was in or out of the fence.

Your explanation makes more sense but it does make the initial action by the app on the phone, as opposed to any polling by the ST server to my location as given by my provider. In the latter description the app seems to merely set the fence and not monitor it. In your description the app is the main player and is actually monitoring the phone.

All very confusing.

I downloaded the IFTTT app. Can you tell me how to use it to open my garage door when I’m approaching. I have the Smartthings Hub setup.