The compass: types and use
A basic compass consists of a magnetic needle, a degree scale (azimuth ring), and a direction-of-travel arrow. The prismatic compass (military) or the baseplate hiking compass are the most commonly used types in the field. Choose a compass with luminescent markings for night use. Keep the compass away from metal objects and electronic devices, which can deflect the needle.
Measuring a direction on the map
Step 1: place the compass edge along the line from your position to the destination on the map. Step 2: rotate the compass dial until the North arrows on the dial are parallel to the map meridian lines (with North upward). Step 3: read off the compass value at the direction-of-travel arrow. Step 4: apply the magnetic declination correction (in the Netherlands approximately 2 degrees — in practice negligible for most applications).
Following a direction in the terrain
Hold the compass horizontally in front of your chest. Turn your body until the magnetic needle points to the set bearing. Look straight ahead and identify a prominent object on that azimuth — a tree, a rock point, a building corner. Walk towards that object, not while staring at the compass. Having arrived at the object, repeat the procedure.
Combining MilMap and compass
Export your route as a PDF with azimuth headings per segment from MilMap. In the PDF route book, alongside each waypoint name, the distance and direction to the next point are shown. In the field: check the bearing on the compass, identify the terrain, and navigate. MilMap's MGRS coordinates for each waypoint are the backup if you lose orientation.
Compass navigation in low visibility
In fog, rain, or snow you fall back on pure compass navigation. Maintain a tight course by calibrating regularly: after every 100 metres check whether you are still on the correct azimuth. Pace count provides the distance. Combine bearing and distance with terrain features from your MilMap preparation: "after 400 metres on bearing 285° the terrain rises — that is the ridge I am looking for."
Deviations and errors
The most common mistake is inaccurate reading due to haste. Take time with the compass: miss one degree and after 1 km you are 17 metres off course. Local magnetic anomalies (iron ore in the ground, nearby vehicle) can deflect the needle. Always check that the needle swings freely and does not stick to the housing.