Making Sense Out of North

East is Least and West is Best
  |  Gorp.com
Trueing your GPS
Trueing your GPS

Second article in a seven-part series

Navigators invented lots of cute rhymes to help us recall how to take declination into account, but I find it easiest to just remember that when I'm hiking anywhere to the east of the agonic line my compass needle leans west, and anywhere west of the line it leans to the east. The amount of local declination is given on most topographic maps, so it's an easy matter to turn the map that number of degrees and straighten it up until the edge is pointing to true north, the way it was drawn. Here's how it works.

Be True to Me!
Walking around in the bush with a compass constantly pointing 14 degrees west of true north (as it is where I live) is a pain, but salvation is at hand in the form of an adjustable compass. All the major brands make them, and using one is simple.

Read the amount of local declination from the map.
Check the year the map was published and add or subtract the annual change.
Dial the local declination according to the compass maker's instructions.
Your compass now points to true north when you match the needle with the base line.
Remember to reset the compass declination when you move to a new area and a new map.

Two Out of Three
Now that we have our compass and map synchronized to true north, what about our GPS?

Fortunately, the engineers took this into account when they developed their GPS software. Looking in the setup directory we'll find an option for setting the unit to read to true north.

Once we've done this our GPS will give all bearings and tracks relative to true and in total agreement with map and compass. True, true, and true. No more worry about declination for the rest of the trip unless, of course, we move to an area and map with a different amount of declination. Still, we'll only have to adjust the compass to keep life simple.


Published: 30 Apr 2002 | Last Updated: 15 Sep 2010
Details mentioned in this article were accurate at the time of publication

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