A compass does three things: tells you which way is north, lets you take a bearing from a map to follow on the ground, and lets you take a bearing from a landmark to find where you are. All three are learnable in an afternoon and all three fail if you skip declination.
- 1
Know the parts
A baseplate compass has a clear rectangular base with a direction-of-travel arrow, a rotating bezel marked in degrees, a magnetic needle with a red north end, and an orienting arrow inside the housing. The clear base is what lets you lay it on a map and read through it.
- 2
Set declination first, once
Declination is the difference between true north and magnetic north at your location, printed on your map. Better compasses have an adjustable declination screw — set it once for your region and every subsequent bearing is corrected automatically. Without adjustment you must add or subtract manually every time, which is where errors creep in.
Reading a topo mapWhere to find the declination noteRead Guide → - 3
Take a bearing from the map
Lay the compass edge along your route from where you are to where you want to go, with the direction-of-travel arrow pointing the way you want to travel. Rotate the bezel until the orienting lines align with the map's north-south grid lines, north up. Read the number at the index. That is your bearing.
- 4
Follow the bearing on the ground
Hold the compass flat in front of you, turn your whole body until the magnetic needle sits inside the orienting arrow, and walk in the direction the travel arrow points. Do not stare at the compass while walking — pick a distinctive object on that line, walk to it, then take a new sighting. This is far more accurate over distance.
- 5
Find your position by triangulating
Identify two or three known landmarks. Take a bearing to each, then draw those lines backward on the map from the landmarks. Where they intersect is roughly where you are. Three lines produce a small triangle rather than a point, and the middle of that triangle is your position.
- 6
Keep metal and magnets away
Phones, knives, trekking pole tips, belt buckles, and vehicle bodies all deflect the needle. Step away from anything metal, and hold the compass away from your body before trusting a reading.
Three Core Skills
| Skill | Use it when |
|---|---|
| Orienting the map | Getting your bearings at a junction |
| Map to ground bearing | Travelling off-trail or in poor visibility |
| Ground to map bearing | Identifying a peak or feature |
| Triangulation | Establishing position when unsure |
| Back bearing | Retracing your route |