Navigating the Woods

Jim Freed, WSU Extension Stewardship Forester

When you’re working with maps and a compass to determine your property boundary you will often hear the term “declination” used.

Declination is used to match up your magnetic compass bearings with the true bearings or azimuths used with your maps. You see, the compass is pointing towards magnetic North Pole, and the map is pointing toward the geographic North Pole, and that is not the same place. So now you must add or subtract an angle between magnetic north and geographic north. 

If your land is in Washington State your declination will be east. That means that you will need to adjust your compass to reflect that east declination.

There are different declinations for all areas of the State of Washington. For example, the declination for Seattle is 16 degrees. If your compass has a declination adjustment screw on it, you will turn the screw so that the compass moves counterclockwise. So if you start with your arrow pointing to 0 or 360 then you will adjust it so the arrow will be pointing to 16 degrees. With this new setting you will be able to take your map and walk the boundary of your property and be very close to what the survey shows for your property.

One of the easiest websites to use for declination settings is the NOAA website. You can enter the latitude and longitude of your location and it will calculate your declination. Click here to visit the NOAA website.