Standing out with colour: signal panel, flag, clothing

Our eyes respond especially to three things: colours that do not fit the surroundings, shapes that look man-made, and movement. Nature consists mostly of green, brown and grey. Fluorescent orange, red and yellow rarely occur there over large areas and therefore stand out strongly. Against snow it is the other way round: dark colours stand out.

Shape matters too. A cloth spread flat and stretched with straight edges looks man-made; a crumpled bundle looks like a stone or a bush. Large, regular shapes are easier to recognise from the air than small, irregular ones.

Movement is the strongest signal as long as someone is looking. A cloth waved in large arcs draws the eye at once. A cloth laid out or a flag on a stick, on the other hand, works continuously – even while you rest or sleep.

Find an open spot that is easy to see from above and from the sides: a clearing, a knoll, a shore or a snowfield. Nobody can see your cloth under trees. Spread it flat and as large as possible and weigh down the corners with stones, so the wind does not carry it away or crumple it.

A flag on a long stick at a raised point is visible from the side too, for example to people on an opposite slope. When you hear or see an aircraft, take a cloth and wave it in large arcs. Then you can show the Y signal with your arms – both arms raised diagonally for 'We need help'.

An emergency blanket is versatile: the shiny side reflects sunlight and can act like a large mirror; the coloured side (often gold or orange) provides contrast. If you wear conspicuous clothing or carry a small orange cloth, you improve your chances without carrying much extra weight.

A helicopter's downwash is very strong. Loose cloths, tarps and emergency blankets can be lifted and drawn into the rotors – that endangers the aircraft and everyone on board. As soon as a helicopter approaches to land, gather up loose items or weigh them down firmly. Keep your distance and follow the crew's signals.

In the cold, warmth comes first. Do not lay out your own insulating layer – jacket, fleece, sleeping bag – as a signal if you need it to stay warm. Hypothermia can become more dangerous than waiting a few hours longer. Use additional items instead: pack cover, tarp, spare clothing, emergency blanket.

Coloured signals only work in daylight. In fog, dusk and night they are useless; then a lamp and a whistle help. In dense forest without a clearing they achieve little, because the canopy blocks the view from above. They work best in an air search and when you are waiting at a fixed place.

Colour complements other signals well: a ground sign made of branches becomes even more conspicuous with an orange cloth in the middle, and a signal mirror catches the eye before the cloth is recognised. If you have a phone with signal, call the local emergency number first (112 in the EU); the cloth then helps rescuers find you over the last stretch.

Survival manuals have long recommended bright colours and high-contrast shapes for being found from the air. That is why life jackets, life rafts and much emergency equipment come in signal colours.

On water, orange cloths and dye markers are common signalling aids. In addition, slowly and repeatedly raising and lowering the arms outstretched to the sides is one of the internationally recognised distress signals at sea. If you just want to wave cheerfully on the water, keep that in mind – it could be taken as a distress sign.