CHAPTER 4: LESSON SPECIFICATIONS
COURSE TITLE: RED STAR COURSE
CTS NUMBER:
ENABLING OBJECTIVE AND TEACHING POINTS
MAP AND COMPASS:
405.09
1.
PERFORMANCE — Calculate the magnetic declinaison and
orient a map using the compass.
2.
A-CR-CCP-116/PC-001
TRAINING DETAILS
5.
TIME — Three 30 minute periods.
6.
METHOD/APPROACH:
a.
lecture;
b.
demonstration; and
c.
performance.
CONDITIONS:
a.
b.
Given — a map;
— a compass and suitable outdoor area; and
Denied — assistance.
7.
SUBSTANTIATION — This lesson will assist the cadet in
choosing the correct direction to travel.
4-49/4-50
3.
STANDARD — The cadet will correctly orient a map using the
compass.
8.
4.
a.
Cadet Reference Book (pages 5.37 to 5-42);
a. magnetic declinaison;
b.
B-GL-382-005/PF-001 (arts 710-805); and
b. calculate the declinaison;
c.
Master Lesson Plan.
c. setting the declinaison on a compass; and
9.
TRAINING AIDS — Maps and compasses.
d. orient the map with a compass.
10.
TEST DETAILS — As per the Standard Statement.
11.
REMARKS:
TEACHING POINTS — Orient a map using a compass.
REFERENCES —
This lesson is best taught out of doors;
b.
Let the cadets calculate their magnetic declination and practice
orienting their maps to the ground; and
c.
If using a local map, demonstrate the effect of declination on
orienteering a map (with and without). This physical
representation of declination is a useful learning tool.
A-CR-CCP-119/PH-001
a.
A-CR-CCP-121/PT-001
MILS AND DEGREES
The degree system of bearings shares some structure and terminology
with units of time. There are 360 degrees (360°) in a circle. There are
60 minutes (60’) in a degree, and there are 60 seconds (60”) in a
minute. It is common to only divide degrees into minutes, and to use
decimals of minutes instead of seconds (e.g. 1.5’ instead of 1’30”).
Mils is a metric-like system for dividing a circle. A circle is divided
into milli-radian and there are 6318 milli-radians in a circle. But 6318
is not a convenient number for simple math, so map users commonly
use 6400 mils in a circle. At one km each mil is about one metre wide.
In certain calculations, or when using a compass with dial graduations
in degrees, you may need to convert mils to degrees or degrees to mils.
For conversion purposes, there are 18 [17.78] mils in one degree.
EO 405.09: MAGNETIC DECLINAISON AND
ORIENT A MAP USING A COMPASS
Having an oriented map is the key to successful navigation. When poor
visibility, or lack of identifiable landmarks, inhibits orienting by
inspection, a quick and accurate orientation can be accomplished using
your compass. The natural tendency of a magnetic compass to point
north has help travelers for centuries keep their maps orientated.
However, as we know, a magnetic compass points to Magnetic North,
not True North, so orienting a map accurately requires a map user to
compensate for the difference.
MAGNETIC DECLINATION
‘Magnetic declination’ is the difference between true North and
Magnetic North, and it is measured in degrees and minutes.
Declination will change, not only depending on your geographic
position, but also annually due to the shifting magnetic pole. There are
only two lines in the Northern Hemisphere where the Magnetic and
True Norths line up equaling a declination of 0° – one line running
through central Canada and one through Russia. Declination is further
described by stating whether the declination is East or West of True
North.
5-37
A-CR-CCP-121/PT-001
Magnetic Reference Field Models – are created to assist mapmakers
in printing accurate and up to date declination information on their
maps (right margin). Since the magnetic field is constantly moving, it
is not useful to just print the last known declination on a map, as a map
may not be reprinted for years and the declination will change in that
time. By analysing the historical data of declination, a mathematical
routine called a magnetic reference field model is created, from which
declination can be calculated. Global models are produced every five
years. These constitute the series of International Geomagnetic
Reference Field (IGRF) models. The Canadian Geomagnetic
Reference Field (CGRF) is a model of the magnetic field over the
Canadian region. It was produced using denser data over Canada than
were used for the IGRF, and because the analysis was carried out over
a smaller region, the CGRF can reproduce smaller spatial variations in
the magnetic field than can the IGRF. The above declination chart is
based on the CGRF. It is generally agreed that the IGRF achieves an
overall accuracy of better than 1° in declination. The accuracy of the
5-38
A-CR-CCP-121/PT-001
CGRF, in southern Canada, is about 0.5°. The accuracy of all models
decreases in the Arctic near the North Magnetic Pole.
Using this model, mapmakers print the declination as it was
determined for the year closest to the date the map was made, as well
as the information about the annual change that a map user can employ
to calculate reasonably accurate declination for the current year. The
year that the declination information was accurate is printed along with
the annual change information under the declination chart in the map
margin.
The act of calculating current declination is far simpler than
understanding the above theories. Trust me.
CALCULATE DECLINATION
To calculate current declination using the information provided by the
declination diagram (and information printed directly underneath) is
just a matter of simple math.
East declination
West declination
To calculate declination we always use the declination stated between
Magnetic North and Grid North – ignoring True North. This is because
bearings taken from a map use Grid North as their point of reference.
5-39
A-CR-CCP-121/PT-001
The annual change noted under the diagram will be either ‘increasing’
(the declination is getting larger), or ‘decreasing’ (getting smaller). The
total annual change will then be added or subtracted from the original
declination in accordance with increasing or decreasing respectively,
to get the current declination.
In the example with east declination – the declination as of 1991 was
E 19°52’ and the annual change decreasing 7.0’. The math goes like
this:
Current year:
Year of declination information:
Difference of years:
2001
-1991
10
Difference in years:
Annual Change:
Total change:
10
x 7.0’
70’
Convert to
degrees and
minutes when
60’ or more.
or 1°10’
Annual change was decreasing so it is subtracted from the original
declination:
Original declination:
Total change:
E 19°52’
-1°10’
Current declination:
E 18°42’
This tells us that the magnetic needle on a compass will point to the
east of grid north by 18 degrees and 42 minutes, for the area depicted
by this map in 2001.
This declination in mils is about 337 mils, that means that if you were
to follow a compass bearing for 1 km without adjusting for declination,
you would be 337 metres off the grid bearing plotted on your map.
This is how important declination is in some parts of Canada.
5-40
A-CR-CCP-121/PT-001
In the example with west declination – the declination as of 1993
was W 13°18’ and the annual change increasing 1.7’. The math goes
like this:
Current year:
Year of declination information:
Difference of years:
2001
-1993
8
Difference in years:
Annual Change:
Total change:
8
x 1.7’
13.6’ or 14’
Round up or
down as
required.
Annual change was increasing so it is added to the original
declination:
Original declination:
Total change:
W 13°18’
+14’
Current declination:
W 13°32’
This tells us that the magnetic needle on a compass will point to the
west of grid north by 13 degrees and 32 minutes, for the area depicted
by this map in 2001.
It is possible to have a very small original declination and a larger total
annual change, so that when you do the math the current declination
actually changes from what was originally a West declination to East,
or vice versa.
To find a precise declination for an area, you can try calling the local
airport's Flight Control Center to get an accurate declination.
SETTING DECLINATION ON A COMPASS
The cadet compass has the advantage of a mechanical device on the
back of the dial that adjusts the orienting arrow to compensate for
declination. The declination scale is in degrees and graduated up to 90
degrees west and east. Ensure that you adjust this device in the correct
direction. Each time you move to a new map area, you will have to
recalculate declination and adjust your compass accordingly.
5-41
A-CR-CCP-121/PT-001
ORIENT YOUR MAP BY COMPASS
To orient your map with a compass:
a. calculate, then set the current declination on your compass;
b. turn the compass dial to read 00 at the luminous index point
closest to the mirror;
c. lay the compass on the map with the mirror pointing North (top
of the map), holding both stable and horizontal;
d. align one side of the compass base plate with an Easting; and
e. holding the map and compass together at your front, turn
yourself until the magnetic needle is directly over the orienting
arrow inside the dial (“Put the red in bed.”).
EO 405.10: MEASURE A MAGNETIC BEARING
The cadet compass is capable of measuring a bearing within 25mils.
There are factors that can cause it to become less accurate:
a. compass error – each compass may have an inherent error from
manufacturing. You would notice this when comparing
bearings taken with one compass, with bearings taken by
others. Most new and well taken care of compasses have no
measurable error;
b. compass deviation – there may be either local geological
abnormalities (e.g. large amount of iron content in rock), or
other factors like using a compass too close to power lines,
wire fence, or vehicles that will cause the magnetic needle to
deviate from an accurate reading. You can lessen this chance
by moving away from obvious sources of magnetic disturbance
or large iron/steel objects – i.e. you will not get an accurate
bearing from inside a car!
c. damage – air can infiltrate the liquid inside the compass dial (a
result of extreme temperatures or damage) forming bubbles
that will effect the movement of the magnetic needle,
sometimes causing error;
d. not holding the compass horizontally causes the needle to try to
pivot at an angle, which, with the cadet compass, will cause the
needle to move less smoothly and possibly create an error; or,
e. you are too close to the magnetic north pole.
5-42
ROYAL CANADIAN ARMY CADETS
Star Program
Master Lesson Plan
RED STAR COURSE
PO: MAP AND COMPASS
ENABLING OBJECTIVE(S):
REFERENCE(S):
A.
B.
405.09: Magnetic Declination and Orient a Map Using the
Compass
A-CR-CCP-119/PH-001 Red Star Course Training Plan; Chapter 4,
Page 4-49/4-50.
A-CR-CCP-121/PT-001 Cadet Reference Book, Pages 5-37 – 5-42.
SUPPLEMENTARY REFERENCE(S): B-GL-382-005/FP-001 Map, Field Sketching and
Compass; Chapter 7, Section 2, Arts 710 & Chapter 8,
Section 2, Arts 805.
TRG AID(S):
A.
B.
C.
D.
E.
F.
STUDENT AID(S):
METHOD:
OHP
OHP Slides
Topographical maps (1 per 2 cadets)
Protractors (1 per 2 cadets)
Compasses (1 per 2 cadets)
Calculator (optional)
A.
B.
Red Star Handbook
Pencil and notebook
Lecture, Demonstration and Performance
REVIEW
I
EO 405.08:
1.
IDENTIFY THE POINTS ON A COMPASS
What are the four cardinal points of the compass?
Answers: North, South, East and West
2.
What cardinal point is found at 180°?
Answer: South
3.
Name two intermediate points of the compass.
Answers: See Page 5-8, CCP-119 Red Star Handbook.
2006-05-04
1/7
TIME: 3 x 30 Minutes
TIME: 5 Minutes
4.
What intermediate point is found between East and South East? What is its value in
degrees?
Answer: East South East; 112.5°
INTRODUCTION
TIME: 2 Minutes
WHAT:
During this period of instruction the cadet will learn how to calculate magnetic
declination and orient a map using a compass.
WHY:
The magnetic declination changes by a small amount every year. We have to account for
this change when taking bearings by using the information on the map. The cadet must
be as accurate as possible when taking bearings. Knowing how to calculate and properly
set magnetic declination, along with orienting a map using the compass will ensure the
cadet is accurate and allow them to travel in the right direction.
WHERE:
It is essential to set the correct magnetic declination for a given area on the compass
whenever cadets are participating in a navigation exercise. If the compass is set properly,
the cadet should reach their destination with few difficulties.
BODY
I
STAGE 1:
INSTR NOTES
MAGNETIC DECLINATION
1.
General Information: Having an oriented map is the key to
successful navigation. When poor visibility, or lack of
identifiable landmarks, inhibits orienting by inspection, a quick
and accurate orientation can be accomplished using your compass.
The natural tendency of a magnetic compass to point north has
help travelers for centuries keep their maps oriented. However, as
we know, a magnetic compass points to Magnetic North, not True
North, so orienting a map accurately requires a map user to
compensate for the difference.
2.
Magnetic Declination: Magnetic declination is the difference
between True North and Magnetic North, and it is measured in
degrees and minutes. Declination will change, not only depending
on your geographic position, but also annually due to the shifting
magnetic pole. There are only two lines in the Northern
Hemisphere where Magnetic North and True North line up
equaling a declination of 0°, one line running through central
Canada and one through Russia. Declination is further described
as East or West of True North.
3.
Magnetic Reference Field Models: This is a model developed
by analyzing the historical data of declination and then creating a
mathematical routine, from which declination can be calculated.
2/7
TIME: 10 Minutes
NOTE: The actual
difference calculated
on the map is the Grid
Magnetic Angle
(GMA). Since the
difference between
grid north and true
north is so small it is
ignored.
There are global models produced every five years by the
International Geomagnetic Reference Fields (IGRF). Canadian
mapmakers use the Canadian Geomagnetic Reference Field
(CGRF), which is a model of the magnetic field over the Canadian
region. The accuracy of the CGRF, in southern Canada, is about
0.5°. The accuracy of all models decreases in the Arctic near the
North Magnetic Pole. Using this model, mapmakers print the
declination as it was determined for the year closest to the date the
map was made, and gives the information required to calculate
magnetic declination:
II
a.
the annual change;
b.
the year that the declination information was accurate;
and
c.
the declination the year that the information was
accurate.
CONFIRMATION STAGE 1
1.
Why do you need to know how to orient a map using a compass?
2.
What is magnetic declination?
3.
What is the Magnetic Reference Field Models?
TIME: 20 Minutes
III
STAGE 2:
CALCULATING MAGNETIC DECLINATION
1.
Annual Magnetic Change: The amount of declination that will
change slightly each year because the magnetic poles shift
slightly.
2.
Accounting for the Annual Change: You must take this change
into account when preparing to take bearings. If you do not
account for it, your bearings will not be accurate. A simple
procedure allows you to update the magnetic declination for any
area if you have the correct map. The map contains all the
information you need. A diagram in the right-hand margin tells
you:
OHP 1
a.
the year the magnetic declination was last updated;
b.
the annual magnetic change; and
c.
the declination when the map data was accurate.
OHP 2
3.
Calculating Magnetic Declination: To update the magnetic
declination for a given map sheet, follow these steps:
3/7
a.
Subtract the year the declination was last updated from
the present year.
EXAMPLE: Refer to OHP 2: 1997 - 1980 = 17
b.
Multiply the answer from Step A by the annual
magnetic change. (The annual change may be in degrees
or mils depending on the map.)
17 X .75 mils = 12.75 mils
c.
If the annual change is increasing, add the answer from
Step B to the declination when the declination was
accurate. If the annual change is decreasing, subtract.
Annual change decreasing:
170.00 mils
- 12.75 mils
157.25 mils
d.
The answer in Step C is the updated magnetic
declination for your map. You would set this on your
compass using the declination adjusting screwdriver before
taking a compass bearing.
e.
You can only set the declination on your compass in
degrees. If you calculated the declination in mils then you
must convert the mils to degrees:
EXAMPLE: 157.25 mils ÷ 17.78 = 8.8°
Note: This declination of 157 mils, means that if you were
to follow a compass bearing for 1 km without adjusting for
declination, you would be 157 metres off the grid bearing
plotted on your map. This is how important declination is
in some parts of Canada.
f.
4.
All locations east of Thunder Bay, Ontario have a
westerly declination. All locations west of Thunder Bay
have an easterly declination.
Adding and subtracting degrees and mils: There are a few
things to keep in mind when calculating magnetic declination:
a.
Mils: When working with mils, it is simply straight
addition and subtraction. Mils can be divided down into
decimal points.
4/7
126.00 mils
+ 35.50 mils
161.50 mils
b.
276.00 mils
- 46.25 mils
229.75 mils
Degrees: A degree is broken down into 60 minutes. The
symbol for a minute is similar to an apostrophe:
25° 14′
+ 6° 49′
32° 03′
14 + 49 = 63 minutes; you must
carry over 60 minutes as 1°; this
means only 3′ left over.
132° 28′ Æ 131° 88′
- 50° 52′ Æ - 50° 52′
81° 36′
28 -52 = -36 minutes; you must carry over a full 60′ so you
do not get a negative result (28 becomes 88; 132 becomes
131).
IV
CONFIRMATION STAGE 2
1.
What is the annual magnetic change?
2.
What 3 pieces of information do you need from the map in order
to calculate the magnetic declination?
3.
OHP 3
OHP 3 gives two examples to go over with the class step by step.
The answers are as follows:
(1) Step A: 1997 - 1988 = 9
Step B: 2.5 mils X 9 = 22.5 mils
Step C: 180 mils + 22.5 mils = 202.5 mils
(2) Step A: 1997 -1982 = 15
Step B: 1.5 mils X 15 = 22.5 mils
Step C: 65 mils - 22.5 mils = 42.5 mils
V
STAGE 3
1.
SETTING THE DECLINATION ON A COMPASS
How to set the declination an a compass: Many compasses,
including the model used by army cadets, have the advantage of a
mechanical device on the back of the dial that adjusts the orienting
arrow to compensate for declination. The declination scale is in
degrees and graduated up to 90 degrees west and east. Ensure that
5/7
TIME: 10 Minutes
you adjust this device in the correct direction by following these
steps when using the SUUNTO MC-1 compass:
VI
a.
Move the end of the orienting arrow to the desired setting
on the declination scale by means of turning the adjusting
screw located on the back of the compass dial;
b.
If the declination in your area is 10° East, turn the
adjusting screw clockwise so the line at the end of the
orienting arrow points to 10° on the west side of the scale;
c.
If the declination in your area is 10° West, turn the
adjusting screw counter-clockwise so the line on the end of
the orienting arrow points to 10° on the east side of the
scale;
d.
Each graduation on the declination scale is equal to two
degrees. If the declination is an odd number i.e. 21°W,
then the line on the end of the orienting arrow must be
centered between 20 and the first graduation after 20 on
the west side of the scale; and
e.
Each time you move to a new map area, you will have to
recalculate declination and adjust your compass
accordingly.
Demonstrate and
have the class set
the declination on
their compasses.
CONFIRMATION STAGE 3
1.
How is the declination scaled and graduated of a compass?
2.
Have the cadets set the declination on a compass for an easterly
declination and a westerly declination.
TIME: 15 Minutes
VII
STAGE 4
ORIENT THE MAP WITH A COMPASS
1.
Orienting by Compass: To set your map by compass, follow
these steps:
a.
Set the magnetic declination for your area on the compass.
b.
Lay the map on a flat surface. Lay the compass on the map in line
with an easting line. (The cover of the compass should point
towards the top of the map).
c.
Set north on the compass dial to the luminous index point.
d.
Rotate the map and compass until the red end of the magnetic
needle is centered inside the orienting arrow.
e.
Your map is now oriented.
6/7
Demonstrate to the
class.
VIII
CONFIRMATION STAGE 4
1.
Note to Instructors: If you have the local maps, take the cadets
outside to practice setting the map by compass. If it is
inconvenient to go outdoors, or if you do not have the right maps,
it can be done in the classroom.
PERFORMANCE CHECK
I
TIME: 26 Minutes
Cadets will calculate without error the magnetic declination for a given map sheet and orient the
map using a compass.
1.
Have the cadets calculate the declination for any available maps, set the declination on
the compass and then orient the map using the compass. Instructors should calculate the
declinations prior to class.
2.
Annex A to this lesson provides some examples for the cadets to practice on. Make
enough photocopies to go around, or copy them on the board.
CONCLUSION
SUMMARY:
RE-MOTIVATE:
TIME: 2 Minutes
A.
During this period of instruction the cadets learned how to calculate
magnetic declination, and how to orient a map using a compass.
B.
Magnetic declination is the difference between a magnetic north and true
north. If the cadets know how to calculate it, they can properly orient a
map using a compass.
A.
Comment on student progress.
B.
Now that the cadets know how to accurately calculate magnetic
declination, they can set their compass for an area with a given map and
use the map and compass together accurately.
C.
This information will be used again for the next lesson in Map and
Compass, which will be Measure a Magnetic Bearing.
7/7
ANNUAL MAGNETIC CHANGE
The amount of declination for any area will change slightly
every year. This difference is called the annual magnetic
change. The older the map, the less accurate the information.
We can account for this
change by using information
found on the map:
1. Year when map data was last
updated
GRID NORTH
MAGNETIC
NORTH
170 mils
2. Annual magnetic change
3. Declination when map data was
accurate
Year of Map Data 1980
Ann. Change Decreasing .75 mils
405.09 Red Star
OHP-1
STEPS IN CALCULATING
MAGNETIC DECLINATION
STEP A: Subtract the year of the map data
from the present year.
STEP B: Multiply the answer from Step A by
the annual magnetic change.
STEP C: If the annual change is increasing,
add the answer from Step B to the declination
when the map data was accurate.
If the annual change is decreasing, subtract.
405.09 Red Star
1997
- 1980
17
17
X .75 mils
12.75 mils
170.00 mils
- 12.75 mils
157.25 mils
OHP-2
CALCULATING DECLINATION
Problem #1:
180 mils
Year of Map Data 1988
Ann. Change Increasing 2.5 mils
405.09 Red Star
Problem #2:
65 mils
Year of Map Data 1982
Ann. Change Decreasing 1.5 mils
OHP-3
ROYAL CANADIAN ARMY CADETS
Star Program
Master Lesson Plan
ANNEX A to EO 405.09 - MAGNETIC DECLINATION
Instructions to Directing Staff
1.
This worksheet will take approximately 10 minutes to complete and correct. The
answers to the questions are listed below.
2.
This activity will give the cadets more practice calculating magnetic declination.
Emphasize these points:
a.
The declination on the map is the angle between magnetic and grid north.
b.
If the annual change is increasing, add. If the annual change is decreasing,
subtract.
c.
One degree (1°) = 60 minutes (60′)
ANSWERS TO DECLINATION PROBLEMS
1.
Year of map data: 1965
Annual change decreasing: .2 mils
Magnetic declination: 165 mils
1997 - 1965 = 32
32 X .2 mils = 6.4 mils
165 mils - 6.4 mils = 158.6 mils
2.
Year of map data: 1991
Annual change increasing: 3.5′
Magnetic declination: 94° 15′
1997 - 1991 = 6
6 X 3.5′ = 21′
94° 15′ + 21′ = 94° 36′
3.
Year of map data: 1982
Annual change decreasing: 3 mils
Magnetic declination: 325 mils
1997 - 1982 = 15
15 X 3 mils = 45 mils
325 mils - 45 mils = 280 mils
4.
Year of map data: 1965
Annual change decreasing: 2.5′
Magnetic declination: 23° 06′
1997 - 1965 = 32
32 X 2.5′ = 80′
23° 06′ - 80′ = 21° 46′
5.
Year of map data: 1991
Annual change increasing: 7′
Magnetic declination: 114° 12′
1997 - 1991 = 6
6 X 7′ = 42′
114° 12′ + 42′ = 114° 54′
ROYAL CANADIAN ARMY CADETS
Star Program
Master Lesson Plan
EO 405.09 - MAGNETIC DECLINATION
Name:______________
Calculate the magnetic declination for the following.
Use a current year of 1997 for all examples:
1.
Year of map data: 1965
Annual change decreasing: .2 mils
Magnetic declination: 165 mils
Step A:
Step B:
Step C:
2.
Year of map data: 1991
Annual change increasing: 3.5′
Magnetic declination: 94° 15′
Step A:
Step B:
Step C:
3.
Year of map data: 1982
Annual change decreasing: 3 mils
Magnetic declination: 325 mils
Step A:
Step B:
Step C:
4.
Year of map data: 1965
Annual change decreasing: 2.5′
Magnetic declination: 23° 06′
Step A:
Step B:
Step C:
5.
Year of map data: 1991
Annual change increasing: 7′
Magnetic declination: 114° 12′
Step A:
Step B:
Step C: