How Come My Compass Doesn’t Work?

Overview

As a teacher on the NB Palmer Totten Cruise in the winter of 2014, I successfully traversed the Magnetic South Pole. This is a wandering point on the Earth’s surface where geomagnetic field lines are directed vertically upwards. As an Outdoor Educator I utilize compasses regularly to navigate. The traverse of the Magnetic South Pole inspired this lesson.

Objectives

Upon completion of this activity, students will understand how a simple compass works and what factors impact their accuracy.

Lesson Preparation

Using various online resources, maps and videos (see resources). Explain that a simple compass utilizes geomagnetic lines to point either to the magnetic North or South Poles. In order to accurately navigate with that compass you would need to factor in the difference between a magnetic and geographic pole. This difference is called declination. Other factors that can divert the magnetic needle of the compass include ferrous metals, motors and other compasses. If these other factors are not close to the compass it will work properly.

Procedure

1. Prior to distributing compasses, explain and diagram the geomagnetic lines of the Earth and the photo of the position of Geographic and magnetic South Pole.
2. Explain how to hold and operate the compass using the worksheet.
3. Have students practice several times how to orient the compass and themselves to a given direction. This could be any degree that is stamped on the compass.
4. Have students walk around and find various objects that cause to the magnetic needle to deviate.

Extension

Breakdown the earth into 360 degrees. Explain that each degree is then divided into 60 seconds. You can then tell them that 1 second of distance on the earth’s surface is equal to a nautical mile. This explains the difference between a regular mile and a nautical mile.

Resources

There are various excellent videos that show simple steps explaining how to orient and use a compass. How to use a compass worksheet (included). In addition I suggest accessing the PolarTREC website and review some of my journal entries.

Assessment

Once the lessons are completed, students should be able to demonstrate how to use a compass and what factors such as the Magnetic poles influencing its accuracy. In addition they should be able to list 2 other devices used to accurately.

Author / Credits

Silva Compass Incorporated.
Adapted by PolarTREC Teacher Glenn Clark <zooclark [at] yahoo.com>