ED 5661 Mathematics & Navigation Teacher Institute
Kevin Murphy
12 August 2011
Grade 11/12
Correcting for Magnetic Variation – Teacher’s Resource Page
Lesson Overview: In this lab activity, students will determine the magnetic variation both from a
rose wheel on a map and for their exact location (using an Internet source). Also, given a
particular displacement (relative to True North), students will convert to a displacement
(relative to Magnetic North).
Sources:



Brogan, Bill. Boat Navigation for the Rest of Us, 2nd Ed New York: International Press,
2001. Print.
Roblee, Stephen . ED 5661 Mathematics & Navigation Teacher Institute. Michigan
Technological University. Houghton, MI, June 2011. Activity 10.
National Geophysical Data Center, Geomagnetism
<http://www.ngdc.noaa.gov/geomag/declination.shtml>
Materials: Navigational Map (provided by instructor) with Rose Wheel, Computer Access or
National Geophysical Datasheet on magnetic (declination) variation.
Vocabulary: (These terms will have been covered in previous classes, but are presented here for
review). Before beginning this activity, please review these terms:




North Magnetic Pole
North Geographic Pole
Magnetic (declination) Variation
Compass Rose
Focus [Pre-Activity] Questions:
1) What angle represents the direction North on a compass rose? South?
2) Where is the North Magnetic Pole currently located?
3) What can be said of the location of North Magnetic Pole (as a function of time)?
Learning Objectives:



Students will be able to add/subtract angles on a compass rose.
Students will be able interpret a map (or table) on a website in order to determine the
local magnetic variation.
Students will be able to move between True North and Magnetic North headings.
Benchmarks:


Illinois Math Performance Descriptor: 9.C.5b Apply physical models, graphs, coordinate
systems, networks and vectors to develop solutions in applied contexts (e.g., bus
routing, areas of irregular shapes, describing forces and other physical quantities).
Common Core State Standards for Mathematics: Geometry, 4G Graph points on the
coordinate plane to solve real-world and mathematical problems.
Activity Description: Students will use a map (attached), which includes a compass rose, in
order to determine magnetic variation. Students will then turn to an Internet source to answer
questions about their local magnetic variation. Finally, students will convert True North
headings to Magnetic North and vice versa.
Assessment: The following questions conclude the activity and serve as an assessment of
students understanding of the concepts.
1. Which city, of those listed below, has the least magnetic variation?
a. New York City
b. Anchorage
c. Honolulu
d. Phoenix
e. Miami
2. You need to pilot a boat on a course of 188° in a channel located in Seattle, Washington.
What course should you take if you are using a magnetic compass?
3. The magnetic compass on your boat reads 72°. What is your actual heading (True
North) if you are traveling in the waters off Chicago, IL?
Correcting for Magnetic Variation
Lesson Overview: In this lab activity, you will determine the magnetic variation both from a rose
wheel on a map and for their exact location (using an Internet source). Also, given a particular
displacement (relative to True North) you will be asked to convert to a displacement (relative to
Magnetic North).
Materials: Navigational Map (provided by instructor) with Rose Wheel, Computer Access or
National Geophysical Datasheet on magnetic (declination) variation.
Vocabulary: (These terms will have been covered in previous classes, but are presented here for
review). Before beginning this activity, please review these terms:




North Magnetic Pole
North Geographic Pole
Magnetic (declination) Variation
Compass Rose
Focus [Pre-Activity] Questions:
1) What angle represents the direction North on a compass rose? South?
2) Where is the North Magnetic Pole currently located?
3) What can be said of the location of North Magnetic Pole (as a function of time)?
Learning Objectives:



You should be able to add/subtract angles on a compass rose.
You should be able interpret a map (or table) on a website in order to determine the
local magnetic variation.
You should be able to move between True North and Magnetic North headings.
Activity Description:
1. Use the compass rose on the attached map to determine the magnetic variation at the
map’s position. Record this value in Table 1.
2. Use an Internet source (such as the National Geophysical Data Center) to determine the
magnetic variation for your location. Record this value in Table 1.
3. Use the values of variation you found in Steps 1 and 2 to complete Table 2.
Table 1
Location
Magnetic Variation
Map
Your Position
Table 2
Location
Map
Magnetic Variation
Compass Heading
270°
Map
Your Position
Heading Relative to
“True North”
90°
60°
Your Position
120°
Assessment Questions:
1. Which city, of those listed below, has the least magnetic variation?
a. New York City
b. Anchorage
c. Honolulu
d. Phoenix
e. Miami
2. You need to pilot a boat on a course of 188° in a channel located in Seattle, Washington.
What course should you take if you are using a magnetic compass?
3. The magnetic compass on your boat reads 72°. What is your actual heading (True
North) if you are traveling in the waters off Chicago, IL?