How GPS can help during an emergency
GPS is routinely confused with mobile data, and that confusion costs people real capability. Your phone can tell you exactly where you are in a place with no signal whatsoever — and knowing how to read and pass on that position is one of the highest-value skills in an emergency.
This is how it actually works and how to use it.
GPS is not the internet
GPS satellites broadcast continuously. Your phone listens and calculates its own position from the timing differences between signals. It never transmits anything back, and it does not need a mobile network.
What needs a connection is the map. A map app that appears broken with no signal has not lost your position — it has lost the map tiles to draw it on. Download the area in advance and both halves work.
Caching map areas so your position has something to sit onOffline mapsCoordinate formats, and which to use
The same position can be written several ways. Giving the wrong format to the wrong person wastes time.
Decimal degrees
Looks like 51.5074, -0.1278. This is what apps and websites use. It is compact and precise, and it is the worst format to read aloud — a string of decimals is easy to mishear or transpose.
Degrees, minutes, seconds (DMS)
Looks like 51°30′26″N, 0°7′40″W. This is the format to use on a phone call or a radio. The numbers are short and the units break them into distinct chunks, which makes errors far less likely.
UTM
A metric grid reference. Common in land-based mapping, surveying and some rescue services, because grid distances are straightforward metres rather than degrees.
Reading your position in all three formatsGPS locationHow to give your position to emergency services
- Say the format before the numbers: "I have a GPS position in degrees, minutes and seconds."
- Read it slowly, and read north/south and east/west explicitly rather than using minus signs.
- Ask them to read it back to you.
- Give the accuracy figure if your app shows one — "accurate to about 5 metres" tells them how tightly to search.
- Say what time the reading was taken if you have moved since.
If you are texting rather than calling, put the coordinates in the message body as plain text. A link to a map needs a data connection at the other end and may not open at all.
Getting a good fix
- Go outside, or as close to it as you can, with a clear view of open sky
- Stand still — a moving phone takes longer to settle
- Give it up to a minute from cold, longer under tree cover or between tall buildings
- Watch the accuracy figure; wait for it to stop improving before writing the position down
- Write it on paper as well. Coordinates survive a dead battery only if they exist off the phone
Accuracy in the tens of metres is normal and perfectly useful. Accuracy of several hundred metres usually means the phone is estimating from cell towers rather than satellites, and is worth waiting out.
Tracking a route, not just a point
A single coordinate says where you were at one moment. A recorded track says where you have been, which for a moving person is considerably more useful to a search team.
Some apps record a position periodically during an alert and can export it as a GPX file — a standard format that mapping and rescue software reads directly. If you are moving, that track is the difference between a point search and a corridor search.
Location logging during an SOS activationSOS alerts