Determining local magnetic declination by a magnetic compass

by tonytran2015 (Melbourne, Australia).

#compass, #magnetic compass, #determine, #find North, #finding North, #magnetic declination, #Magnetic North, #sunrise, #sunset, #True North

A magnetic compass can be used to determine local magnetic declination. This declination varies with location and time.

Magnetic Declination

Figure: True North, Magnetic North and Magnetic Deviation.

The declination is compiled from local laboratories data and made into world charts for navigation but each person can also determine his current local declination by himself.

Step 1: Requirements

Compass Magnetic

Figure: Magnetic compass, dry, eddy-current-damped, ex-US Army.

We require:

1. A place where both Sunrise and Sunset can be observed,

2. Parallel magnetic field lines for the whole place, that is the direction of the magnetic needle does not change when the compass is moved around in such a place, and

3. A sighting compass as in the picture.

Step 2: Determining local magnetic declination.

Keep the sighting compass level and read the direction of Sunrise.

Keep the sighting compass level and read the direction of Sunset.

The bisector line of the two readings is the true North. The reading for the bisector is the mean value of Sunrise and Sunset values.

The reading of the bisector line is the absolute value of magnetic declination. Magnetic declination is positive when magnetic North is East of true North and negative when West.



Finding North with a lensatic compass, posted on August 21, 2017


, posted on June 14, 2016


Selecting and using magnetic compasses, posted on July 9, 2016


Navigating with an AM MW radio receiver, posted January 17, 2017The Scorpius constellation, posted January 8, 2017, The Orion constellation., posted December 26, 2016, Rice as emergency food.Using GPS in off-grid situationsSlide Sky-Disks with grid masks showing azimuths and altitudesSlide Sky-Map for displaying tropical stars.

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3 thoughts on “Determining local magnetic declination by a magnetic compass

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