SHOULD I USE THE DECLINATION ADJUSTMENT ON MY COMPASS?
SHOULD I USE THE DECLINATION ADJUSTMENT ON MY COMPASS?
High-end compasses have an adjustable declination correction: once set to the local magnetic declination, the compass can be used with a map without having to do the conversion between magnetic and true or grid bearings.
ADJUSTING THE MAGNETIC DECLINATION
HOW IS IT DONE?
Setting the declination on a compass varies from brand to brand. Usually it requires an adjustment key, although some brands are tool-free!
By default a compass is set to a magnetic declination of 0°. Adjusting the magnetic declination involves rotating the compass North Orienting Arrow so that it matches the local magnetic declination or grid/magnetic angle, east or west.
SHOULD I USE THE MAGNETIC DECLINATION OR THE GRID/MAGNETIC ANGLE?
Use the grid/magnetic angle value if you are working with magnetic and grid bearings! Use the magnetic declination value if you are working with magnetic and true bearings!
THEN WHAT?
You are likely to work with grid bearings so you will adjust for the grid/magnetic angle on your compass! The magnetic needle of the compass is unchanged and points towards the Magnetic North.
When taking grid bearings on a map, proceed as usual: align the orienting lines with the grid lines on the map and read the grid bearing on the index line. Orientate yourself so that the compass needle is aligned with the orienting needle and navigate! No conversion needed!
PROS AND CONS OF ADJUSTING YOUR COMPASS
Adjusting for the declination in your compass has pros and cons.
PROS
- All your bearings are grid (or true).
- You do not need to make any conversion.
CONS
- You need to adjust the declination or magnetic/grid angle on your compass whenever you change location.
- You may forget how magnetic declination works.
- The adjustment can only be done on some compasses.
- If someone borrows your compass, remind them that it is set for some declination or magnetic/grid angle value!
At the end of the day, this is your decision!
I do not correct my compass and I do the conversion between grid and magnetic bearings.
