The Silvertree Reach can obtain your loved one's location from four different connection sources.
They are:
GPS/LTE : with a subscription/membership, the Silvertree Reach will power on its GPS and LTE chips to track your loved one remotely. See How does my Silvertree Reach use GPS/LTE?
The Silvertree App : when you are close by a device with the Silvertree App, the app automatically leverages your mobile's location to preserve the Silvertree Reach’s battery life.
Wi-Fi: The Silvertree Reach can see close-by WiFi networks and use them to determine your loved one’s location. (Note: the Reach does not need to be connected to your home WiFi network to use this feature, but being connected to your home WiFi network will improve the Reach’s battery life and is recommended anyway)
See here how location affects battery life.