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Eastern Washington Orienteering Club

Using A Compass With A Map


Place the direction of travel line along your intended route…

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Now we'll look at how to use a thumb compass, illustrated to the left. A thumb compass is a smallish compass designed to be strapped to your thumb. (They're available in left or right-hand models.) The design is supposed to make it easy for you to hold the map, and the compass on top of it, with one hand.

Start by placing the direction-of-travel line of the compass along your desired route. Remember: in this example we're planning on going from control 4 to control 5.

Bonus Details

The distance between magnetic north lines is consistent (often 250 meters, real world) so that you can estimate distances quickly
Compasses point to magnetic north. In Spokane that means your compass will point about 14-1/2 degrees east of true north (the line that streets generally correspond to). That "error" is known as declination — as in "14-1/2 degrees east declination."
The declination varies by region, and slowly over time. 40 years ago, the declination in Spokane was about 5 degrees greater.