Electronic navigation devices require electrical energy and satellite reception. If one or the other is not available, these devices are only of limited use.
A navigation satellite receiver can only provide precise position and time information outdoors and in the field of view of several satellites. The use of such devices in caves, tunnels and tunnels makes little sense because there is no reception there.
The clock of navigation devices is extremely accurate and can be used as a reference time for setting other clocks. Most navigation devices now support not only the American Global Positioning System (GPS), but also the European GALILEO, Russian GLONASS and Chinese BEIDOU systems. This brings higher resolution and better availability of the service.
Knowing your own position in the landscape (coordinates) can be of great help to you or to others (e.g. caregivers, search teams).