Compass Declination. Why it doesn’t matter explained . Impact On Land Navigation, by Very Survival on YouTube. 27 min 18 s.
- Video length
- 27 min 18 s
- Time to do it
- 15 minutes
- Difficulty
- Easy
- Steps
- 9
What you need
Steps
Find the declination value for where you are navigating. Check the declination website or the declination diagram printed in the margin of your topographic map.
Note whether declination is east or west. Write the number and direction down so you do not confuse the sign later.
Understand the three norths: true north on the map, magnetic north that the needle points to, and grid north on your map grid. Declination is the angle between true and magnetic north.
If your compass has an adjustable declination screw or scale, set it to your local value. Turn the screw until the orienting arrow shifts by the correct number of degrees.
If your compass has no adjustment, remember the rule: add east declination and subtract west declination when converting a map bearing to a magnetic bearing.
Take a bearing from the map by lining the compass edge between your position and your target. Rotate the bezel until the orienting lines align with the map grid lines.
Read the bearing at the index line. Apply your declination correction to get the magnetic bearing you will follow in the field.
Hold the compass flat and turn your body until the red needle sits inside the orienting arrow. Walk in the direction of the travel arrow.
Check your bearing again after a few hundred meters or at any major landmark. Recalculate if you have moved far enough for declination to change.
Tips and common mistakes
Do not ignore declination in areas with large values, since a 15 degree error puts you far off course over a long distance.
Keep metal objects, phones and magnets away from the compass when you take a bearing.
Write your corrected bearing on the map so you do not have to redo the math in bad weather.
Check the declination date on older maps, because the value drifts slowly over the years.
Questions
Do I need to adjust declination if my compass has no screw?
No. Leave the compass at zero and do the math yourself each time you convert a map bearing to a magnetic bearing.
How do I know if declination is east or west?
Look at the declination diagram on your map. If magnetic north sits to the right of true north, it is east declination.
Does declination matter for short walks?
It matters less over short distances, but it still adds error. Correct it whenever you are following a bearing for more than a few hundred meters.
This guide was drafted from the video's details and general task knowledge. It has not been checked against the full video. Check the video and relevant product instructions before following a procedure. Report a correction.
