Three norths
Navigation distinguishes three references. True north points to the geographic pole. Grid north follows the vertical grid lines on the map, which differ slightly from true north because a curved earth is drawn on a flat grid. Magnetic north is where the compass needle settles, and it drifts over time. The angle between grid and magnetic north is the magnetic declination, and it must be accounted for when a bearing taken from the map is walked in the field.
Magnetic declination changes by location and slowly over the years, so it is read from a current source rather than memorised. For Germany, present-day values can be looked up through the geomagnetism service of the GFZ German Research Centre for Geosciences.
Orienting the map
Orienting means turning the map so its features line up with the ground. The simplest method uses terrain: rotate the map until a visible feature such as a road, a lake shore or a prominent ridge matches its drawn position. With a compass, place the map flat, lay the compass on it, and turn the map until the needle and the map’s north align — adjusting for declination. An oriented map makes left and right on paper match left and right in front of you.
Taking a bearing from the map
To travel from one point to another along a straight line:
- Place the edge of the baseplate along the line from your position to your objective, with the direction-of-travel arrow pointing toward the objective.
- Rotate the bezel until its orienting lines are parallel with the map’s grid lines and its north mark points to map north.
- Read the bearing at the index. This is a grid bearing.
- Adjust for declination to convert the grid bearing into the magnetic bearing you will follow.
Following the bearing on the ground
Lift the compass from the map, hold it level in front of you, and turn your body until the needle sits inside the orienting arrow of the bezel. The direction-of-travel arrow now points along your route. Rather than staring at the needle while walking, pick a visible feature on that line — a distinct tree or rock — walk to it, then sight the next one. This keeps a straight course and frees your attention for the terrain.
Practical techniques
Handrails and catching features
A handrail is a linear feature — a path, fence line or stream — that runs near your route and can be followed instead of a strict bearing. A catching feature is something beyond your target, such as a road or river, that tells you when you have gone too far.
Aiming off
When aiming for a point on a line such as a bridge on a river, deliberately aim to one side. On reaching the river you then know which way to turn, instead of guessing whether the bridge is upstream or down.
| Term | Meaning |
|---|---|
| Declination | Angle between grid north and magnetic north at a place and time |
| Bearing | A direction measured in degrees from north |
| Handrail | A linear feature followed alongside the route |
| Catching feature | A feature past the target that signals an overshoot |
| Aiming off | Aiming to one side of a point on a line on purpose |
Current magnetic declination values can be obtained from the GFZ German Research Centre for Geosciences, gfz.de.