Reading and sharing your location: coordinates, apps, description

The GPS receiver in your phone (or a similar satellite system) calculates the position from the signals of several satellites. It needs neither mobile network nor internet for this, only as open a view of the sky as possible. With a data connection the phone often finds its position faster because it gets helper data from the network; without a network the first fix can take a little longer. To send the position to someone else, however, you always need a network – mobile, Wi-Fi or a satellite device.

In many countries the phone automatically sends its location to the control centre during an emergency call; in Europe, for example, through a system called AML. This is a big help, but it is not available everywhere and not reliable in every situation. So you should still be able to read and state your location yourself.

Some apps package coordinates into a link, three words or a short character code. This is convenient to say aloud, but it only works if the other side knows the system and can decode it. When in doubt, also give the normal coordinates.

Coordinates come in several notations, and this is where most mistakes happen. Common ones are decimal degrees (for example 47.5 degrees north), degrees with minutes, degrees with minutes and seconds, and grid coordinates such as UTM. 47.5 degrees is not the same as 47 degrees and 5 minutes – 47.5 degrees equals 47 degrees and 30 minutes. Mixing up formats can quickly send rescuers to a place far away. So state the format first, then the numbers.

Say the digits slowly and one by one, add north or south and east or west, and have the numbers read back to you. Write them on paper before you call – under stress it is easy to lose track. Also wait a moment under open sky until the displayed accuracy no longer changes much. Many apps show this as a circle or a figure in metres.

Always add a description to the coordinates: which path, what altitude, which body of water, below which summit, what you can see and hear. This description is the safety net in case something goes wrong with the numbers.

Before a trip it is worth giving a trusted person your trip plan and sharing your live location on the way, or sending a message with your position now and then. If you do not come back as planned, that person knows where the search should start. A text message often still gets through on a weak signal when a call or mobile data no longer work.

When meeting others – at a car park in the woods or at an event, for example – a shared location is far more precise than 'we are by the big tree'. And in an emergency you can read the coordinates out to the control centre even if automatic location has not worked.

Sending your location to friends is no substitute for an emergency call. In an emergency, always first call the local emergency number (112 in the EU), then inform relatives if needed. In areas with no network at all, only satellite devices, signals or a trip plan left beforehand will help.

Permanent location sharing uses battery and reveals a lot about you. Share your location deliberately, only with people you trust, and end the sharing after the trip. Save the battery for emergencies: flight mode or power-saving mode when you do not need the phone, and a power bank for longer trips.

Find out today where your phone shows coordinates – in the map app, a compass app or an offline map app – and in which format. Read them out loud once as if you were passing them on in a call. Also try sending your location by message and how to start and stop live sharing.

Practise in pairs: one person reads out their coordinates, the other enters them into a map app. Does the point land in the right place? This quickly shows where mix-ups happen, and you will be calmer in a real situation.