Figure 1 is an illustration of a person using compass to determine the compass and grid bearings near Ottawa. A tree is used as reference. The magnetic bearing of the tree is 80 degrees (by compass) but is 67 degrees by map grid. To determine grid bearings near Ottawa, find the magnetic bearing and subtract 13 degrees. In Vancouver, where the declination is 21 degrees east, you would find the magnetic bearing and add 21 degrees to get a grid bearing.