Topographic maps are drawn to true north (North Pole), which is indicated by the grid lines on the map. However, a compass will always point to magnetic north, which is in the Hudson Bay area. The difference between true north and magnetic north is called “declination.”
When true north and magnetic north are aligned, you’re at zero degrees declination. Your compass needle will point to true north. However, if you’re east or west of zero degrees declination, your compass will not be in line with true north.
To compensate for declination:
- Center the north arrow (the N) of the compass dial along a north/south line of the map.
- Check the diagram at the bottom of the map that shows whether magnetic north is to the left or right of true north.
- Turn the compass dial the correct number of degrees left or right as indicated on the map. The N is now pointing at magnetic north.
- Hold the compass level in front of you and rotate your body until the tip of the compass needle aligns with the N on the compass dial. The direction arrow on the base plate now points in the direction you want to go.