Can I rely on my phone to navigate on a hill?

Mapping apps have made navigation far more accessible, and it is not sensible to be sniffy about them: knowing precisely where you are, on demand, is something no paper map has ever offered. The problem is not accuracy, it is dependence. The realistic position is that a phone is your primary convenience and paper is your primary reliability.

Safety

What you'll need

• A mapping app with proper OS or equivalent mapping
• Offline maps downloaded before leaving
• A paper map and compass
• A power bank and cable
• A waterproof case or bag

Step by step

1. Understand what the phone is actually doing.GPS position comes from satellites and works without any mobile signal. The map tiles do not — they are downloaded over data unless you have saved them. That is why people find themselves with a blue dot on a blank grey screen in the middle of nowhere.
2. Download the offline maps before you leave the house.Every serious app allows an area to be saved for offline use. Do it on wifi, for a bigger area than your route, and check it actually works by putting the phone in flight mode and opening the map.
3. Plan for the cold.Lithium batteries lose capacity sharply in cold weather and a phone showing 60 per cent can shut down at once when it gets cold and wet. Keep it in an inside pocket against your body, not in a rucksack lid or an outside pocket.
4. Carry a power bank and the right cable.A small power bank doubles or trebles your usable time. Keep it warm too, and check before every trip that it is charged — a flat power bank is dead weight.
5. Turn off what you are not using.Flight mode with location services still on saves a great deal of battery, because searching for a signal in a valley with none is what drains phones fastest. Turn the screen brightness down and let the screen sleep between checks.
6. Waterproof it and secure it.A dry bag or a waterproof case, and a lanyard or a zipped pocket. Wet capacitive screens misread touches badly, and a phone dropped from a summit ridge is gone.
7. Carry paper and know how to use it.A 1:25,000 or 1:50,000 map of the area and a baseplate compass. The skills that matter are orienting the map, taking and walking a bearing, and reading contours — all covered elsewhere and all worth practising in good weather.
8. Use the phone to check, and the map to plan.The most reliable combination is planning and following the route on paper and using the phone to confirm position when in doubt. That way a dead phone changes nothing except confidence.
9. Learn how to get a grid reference and a what3words location out of it.In an emergency, being able to read out an exact position from the phone speeds up a rescue enormously. Find the feature now, not on the day.
10. Do not use a phone as a compass.Phone magnetometers are affected by the phone's own electronics, by metal, and by having been shaken about, and they need recalibration constantly. For a bearing in poor visibility, use an actual compass.

Tips

• A dedicated GPS unit runs on AA batteries you can swap on the hill and survives being dropped, which are its two real advantages over a phone.
• Print or screenshot the route as a backup if you do not have paper, but understand that a screenshot has no position information and no detail beyond what was on screen.
• Register your phone for emergency SMS to 999 now. It works where a voice call will not, and it takes two minutes.
• Watches with mapping are excellent for following a planned route and poor for improvising a new one on a tiny screen.

Common mistakes

• Setting off with the phone as the only navigation — Every one of the failure modes — cold, wet, drop, flat — happens on ordinary British hill days, and they tend to happen together and in bad weather.
• Assuming a downloaded route means downloaded maps — A saved GPX route is a line. Without offline map tiles, that line sits on a blank screen with no context.
• Following the blue dot without looking at the ground — It encourages walking into ground the map would have warned you about, and it stops you building the awareness that lets you cope when the phone stops working.

If it doesn't work

Questions people ask