Lexicon

Declination (angle of declination)

declination is the difference between “true north”- the actual axis of rotation of the globe, and “magnetic north”- the topmost point of emanation of the magnetic field surrounding the globe, to which compass needles point. Declination is expressed as an angle. Looking at a compass with the needle pointing north, the declination to true north will be a few degrees either east or west of the needle, depending on your location on earth. Virtually all topographic maps show the declination for that particular region. However if the map is more than 10 years old, the declination may have changed enough to seriously throw off your attempts to navigate accurately if you use the declination shown on the map