Most mobile devices incorporate a geolocation capability, and the maps in these pages make use of this to find and display your location as you move.
Clicking the button on the map will track your approximate position based on the location of the mobile network masts that your device can “see”, or the wi-fi network you are connected to. If you have signals from several masts at the same time, this can be quite accurate, but if only one is available, possibly several kilometres away from you, your location may jump from place to place as your device is handed over from one mobile mast to another, giving rise to rather odd looking behaviour as you follow your location on a map!
Clicking the button as well will give a much more accurate and frequently updated position, using the Global Positioning Satellite network. GPS operates by using signals from the satellites to calculate your location on the ground. When you switch on your device in a new place, GPS can take some time (it can be a minute or more) to find where you are. After that, it normally updates in a few seconds, but this depends on a number of factors.
To get a fix on your location, your GPS system must be able to receive signals from a minimum of four satellites, and preferably more. In the open air, this is almost always the case. However, the signals are very weak by the time they reach you from satellites thousands of miles away (they orbit the earth at a height of around 20,000 km – 12,000 miles). The metal body of a train carriage, as well as cuttings and tall buildings (and, of course, tunnels) can block out signals, so that sometimes there might not be enough for GPS to operate. If this happens on a ‘phone or tablet that has a mobile network connection, the geolocation system will revert to using the location of the mobile ‘phone aerial mastor wi-fi network that it is connected to.
If GPS stops working when you are in a remote area and have no mobile signal, or if you are using a laptop or other device that has no mobile phone or data capability, then location tracking will stop altogether. Unfortunately, this is a problem that can only be fixed by train designers or network operators, not website and app developers! If it does occur for a prolonged period (2 minutes or more), you may need to use the and buttons to re-start the tracking process.
Because GPS needs a high receiver sensitivity and performs a lot of calculation, it does use up your battery charge faster than other applications.