Map Reading III
Reading a Grid &
Determining Direction
GRC JROTC
COL. ALEXANDER
Map Reading II
Outline
Purpose
 North (3 types)
 Types of Azimuths
 Measuring
Azimuths

Map Reading III
Plotting
Azimuths
 Practical
Exercise
 Summary
 Conclusion

Purpose
To lay the groundwork for
successful map reading and
land navigation by exposing the
cadet to determining grid and
magnetic azimuths using a
protractor and compass.
Map Reading III
North (x3 types)
True
North
Map Reading III
Magnetic
North
Grid
North

True North- line
through North Pole.

Magnetic Northdirection to northern
magnetic pole
(compass).

Grid North-North as
established by map
maker.
Types of Azimuth
An azimuth is an angle measured
clockwise from a base line
direction (north).
Grid- angle between grid north and a
straight line plotted between two points on a
map.
 Magnetic- angle determined by using a
compass.
 Back- opposite direction of an azimuth.

Map Reading III
Measuring an Azimuth
N

Protractors
E
W

Compasses
Map Reading III
S
360 degrees in a CIRCLE
Measuring an Azimuth
Protractors
Map Reading III
Measuring an Azimuth
Compasses
Magnetic Lensatic Compass
(Military Type)
Silva Polaris Compass
(Civilian Orienteering)
Map Reading III
3 Ways to Plot Azimuths
1.
Plotting Azimuths between 2 points
on a map.
2.
Converting Magnetic Azimuths to Grid
Azimuths.
3.
Converting Grid Azimuths to Magnetic
Azimuths.
Map Reading III
Reading a GRID
10-DIGIT GRID:
EG 1 2 3 4 5 6 7 8 9 10
1000M 100M 10M
EG 1
1000M 100M 10M
8-DIGIT GRID:
2 3 4 5 6
1000M 100M
Map Reading III
1M
10M
7
1M
8
1000M 100M 10M
Reading a GRID
08 74 (4 digit)
084 742 (6 digit)
COLUMBUS: 16S
TENINO:
Map Reading III
10T
FL (or GL)
08 45 74 25
Square
Identification
8-Digit
Grid
(w/in 10 M)
EH (or EG)
15 85 82 20
Reading a GRID
76
75
1000 METERS
28
1
0
0
0
2. Then UP
28
M
E
T
E
R
S
1. Read RIGHT
27
27
Map Reading III
75
76
Using a Protractor
MAKE SURE
THAT YOU
USE THE
CORRECT
SCALE for
the MAP you
have
1:50,000
Map Reading III
Using & Reading a Protractor
1 “GRID
SQUARE” =
1000 M x 1000 M
Each # (1, 2, 3, etc)
= 100 METERS
Map Reading III
Each | in between =
50 METERS
25 or
250 M
Slide
protractor
over to the
RIGHT - 45
Line-Up
Vertical Scale
of protractor
with 08 Grid
08
Reading a Protractor
09
75
Move UP 25
& place a dot
or mark
75
UP
RIGHT
74
74
08 45 74 25
Map Reading III
08
09
Use Protractor
MUST BE
PRECISE
MUST slide
protractor to
the RIGHT to
place mark
CAUTION: You can’t put
your pen/marker thru the
plastic edge/overhang !
Map Reading III
.09
2. Then UP
STEP 1. Locate 2 points:
• POS 1- EG1350 8009 and
• POS 2- EG1610 8055 on the map.
TENINO Map Sheet
Point #1
.50
EG 1350 8009
POS 1
1. Read RIGHT
13
80
TENINO Map Sheet; Point #2
.55
EG 1610 8055
80
POS 1
POS 2
.10
1. Read RIGHT
2. Then UP
STEP 1. Locate two points:
• POS 1- EG13508009 and
• POS 2- EG1610 8055 on the map.
STEP 2.
• Connect the points with a straight edge.
• Draw a line extending beyond the
points.
POS 2
POS 1
STEP 3. Place index of protractor on line at a
vertical (North/South) or horizontal (East/West)
grid line. Keep the 0-180 degree line on the
vertical grid line.
POS 2
POS 1
STEP 4. Read the angle value on the grid scale.
POS 2
POS 1
80 degrees
1420 mils
BACK AZIMUTH
RULE #1: IF THE AZIMUTH IS MORE THAN 180 DEGREES,
THEN SUBTRACT 180 DEGREES.
EXAMPLE: AZIMUTH
215 DEGREES
-180 DEGREES
BACK AZIMUTH
35 DEGREES
RULE #2: IF THE AZIMUTH IS 180 DEGREES OR LESS,
THEN ADD 180 DEGREES.
EXAMPLE: AZIMUTH
180 DEGREES
+180 DEGREES
BACK AZIMUTH
360 DEGREES
Map Reading III
3 Ways to Plot Azimuths
1.
Plotting Azimuths between 2 points
on a map.
2.
Converting Magnetic Azimuths to Grid
Azimuths.
3.
Converting Grid Azimuths to Magnetic
Azimuths.
Map Reading III
Plotting Azimuths

Azimuths must be converted to the
environment they will be used in.


Grid to Magnetic (map-to-compass)
Magnetic to Grid (compass-to-map).

Use the Declination Diagram to find the
conversion angle (GM Angle).

For Grid to Magnetic Conversion Remember:
Right-Add-Left-Subtract (RALS):


GM to the Right Add GM.
GM to the Left Subtract the GM.
Map Reading III
Plotting Azimuths;
What is the GM Angle for Tenino?
Map Reading III
Declination Diagrams
What is the GM Angle for Columbus?
Practical Exercise
Question #1:

Given a Tenino Map (hint: find Declination Diagram).

From your location you see a radio tower on magnetic azimuth
of 275 degrees.

What azimuth will you use to locate the radio tower on your
map?

Bonus: What would be the GRID azimuth from the tower to
your position?
Map Reading III
Answer: # 1
MAGNETIC AZIMUTH:
275 DEGREES
WESTERLY G-M ANGLE: + 21 DEGREES
GRID AZIMUTH:
BONUS:
GRID AZIMUTH:
296 DEGREES
296 DEGREES
OPPOSITE DIRECTION: - 180 DEGREES
BACK AZIMUTH:
116 DEGREES
Map Reading III
Practical Exercise
Question #2

Given a Tenino Map (hint: find Declination Diagram).

After determining the map location for your rendezvous with the B
Company platoon leader, you plotted the grid azimuth at 179 degrees.
There are mine fields on both sides of your route so you want to make
sure you travel in the right direction.

What azimuth will you tell your compass man to follow?

Bonus: You got half way to the rendezvous and were directed to
dispatch a squad back to your original location.

What azimuth should your squad leader follow?
Map Reading III
Answer: # 2
GRID AZIMUTH:
179 DEGREES
EASTERLY G-M ANGLE: -21 DEGREES
MAGNETIC AZIMUTH:
BONUS:
MAGNETIC AZIMUTH:
158 DEGREES
158 DEGREES
OPPOSITE DIRECTION: +180 DEGREES
BACK AZIMUTH:
338 DEGREES
Map Reading III
Practical Exercise
Question #3 (TENINO Map)

What TERRAIN FEATURE is located at EG 06159015?

What TERRAIN FEATURE is located at EG 12859835?

What TERRAIN FEATURE is located at EG 10309650?

What TERRAIN FEATURE is located at EG14508545?

What TERRAIN FEATURE is located at EG 02407981?

What TERRAIN FEATURE is located at EG 15329335?

What TERRAIN FEATURE is located at EH 18700030?
Map Reading III
Answer: PE # 3
 What TERRAIN FEATURE is located at EG 06159015? - DEPRESSION
 What TERRAIN FEATURE is located at EG 12859835? - SADDLE
 What TERRAIN FEATURE is located at EG 10309650? – RIDGE
 What TERRAIN FEATURE is located at EG14508545? – CLIFF
 What TERRAIN FEATURE is located at EG 02407981? - DRAW
 What TERRAIN FEATURE is located at EG 15329335? - SPUR
 What TERRAIN FEATURE is located at EH 18700030? - HILL
Map Reading III
Summary




Map Reading III
Purpose
North
Types of
Azimuths
Measuring
Azimuths


Plotting
Azimuths
Practical
Exercise
Conclusion
Successful land navigations starts with
map reading skills. Your ability to
swap information between grid a
magnetic environments is essential
to helping you fight, survive, and win
on the battlefield.
Map Reading III
Map Reading III
Reading a Grid &
Determining Direction
GRC JROTC
COL. ALEXANDER
Map Reading II