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Compass Basics and Taking a Bearing

Point yourself the right way even in fog or forest

The baseplate compass

A baseplate compass has a clear plastic base with a direction of travel arrow, a rotating bezel marked 0 to 360 degrees, a magnetic needle with a red end pointing to magnetic north, and an orienting arrow with parallel lines printed inside the bezel. Hold it flat at chest height, away from phones, metal zips, knives and car bodies, which all pull the needle. Turn your whole body, not the compass, until the red needle sits inside the orienting arrow; this is called putting red in the shed. The direction of travel arrow now points along whatever bearing is set on the bezel.

Three norths

True north is the geographic pole. Grid north is where the map's grid lines point, usually very close to true north. Magnetic north is where the needle points, and it differs from grid north by an angle called declination, which varies by location and drifts every year. In Portugal in 2026 the difference is roughly 1 to 2 degrees west, small enough to ignore on short legs; in parts of North America it exceeds 15 degrees and would put you kilometres off over a long walk. Your map's margin states the local declination and its yearly change. Some compasses let you set it once on an adjustment screw.

Taking a bearing from the map

Place the long edge of the baseplate along the line from where you are to where you want to go, with the direction of travel arrow pointing towards the destination. Ignore the needle entirely for this step. Rotate the bezel until the orienting lines inside it run parallel to the map's north-south grid lines, with the orienting arrow pointing to the top of the map. Read the bearing at the index line where the bezel meets the direction of travel arrow. If declination is west, add it to the number; if east, subtract it. Now the compass is set. Lift it from the map.

Following the bearing

Hold the compass flat and turn your body until red is in the shed. Look along the direction of travel arrow and pick a landmark on that line, ideally 50 to 200 metres away: a distinct tree, a boulder, a corner of a wall. Walk to it without looking at the compass, then repeat. Picking landmarks stops you drifting downhill or around obstacles, which is how people walk in circles. In fog, send a companion ahead to the edge of visibility, line them up with the bearing and walk to them. Count paces on each leg so you also know roughly how far you have gone.

Back bearings and getting unlost

A back bearing is your bearing plus or minus 180 degrees; it points back the way you came, so you can retrace a leg exactly. To check where you are, take a bearing on a visible landmark you can identify on the map, subtract or add 180, and draw that line from the landmark on the map; you are somewhere on it. Do this from two landmarks and you are where the lines cross. If you are truly unsure, stop, sit down, drink, and think before moving. Most people who become lost make it worse by walking fast in the direction they hope is right.

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