Map Reading II

Map Reading IIIReading a Grid &

Determining Direction

GRC JROTCCOL. ALEXANDER

Map Reading III

Outline

Purpose North (3 types) Types of Azimuths Measuring

Azimuths

Plotting Azimuths

Practical Exercise

Summary Conclusion

Map Reading III

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- line through North Pole.

Magnetic North- direction to northern magnetic pole (compass).

Grid North-North as established by map maker.

TrueNorth

MagneticNorth

GridNorth

Map Reading III

Types of Azimuth

An azimuth is an angle measuredclockwise 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

Protractors

Compasses

EW

S

N

360 degrees in a CIRCLE

Map Reading III

Measuring an AzimuthProtractors

Map Reading III

Measuring an AzimuthCompasses

302010

W

E

E. decl.

W.decl.

mm

BASE PLATE

DIRECTION OFTRAVEL ARROW

BASE LINE

INDEX LINE

ORIENTEERINGARROW

ROTATINGDIAL

FLOATINGMAGNETIC

NEEDLE

ORIENTEERINGLINE

N

S

11

/ 21

/ 2

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

8-DIGIT GRID:EG 1 2 3 4 5 6 7 8

1000M 100M 10M 1M 1000M 100M 10M 1M

1000M 100M 10M 1000M 100M 10M

Map Reading III

Reading a GRID

COLUMBUS: 16S FL (or GL) 08 45 74 25

TENINO: 10T EH (or EG) 15 85 82 20

Square Identification

8-DigitGrid

(w/in 10 M)

08 74 (4 digit)084 742 (6 digit)

Map Reading III

Reading a GRID

75

75

27 27

1. Read RIGHT2.

T

hen

UP

76

76

28 281000

METERS

1000 METERS

Map Reading III

Using a Protractor

MAKE SURETHAT YOUUSE THE

CORRECTSCALE 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

Each | in between =50 METERS

25 or250 M

Map Reading III

Reading a Protractor08

08

08 45 74 25

74 74

09

09

7575

Line-UpVertical Scale of

protractor with 08 Grid

RIGHTU

P

Slide protractor over to the RIGHT - 45

Move UP 25 & place a dot

or mark

Use Protractor

Map Reading III

CAUTION: You can’t put your pen/marker thru the plastic edge/overhang !

MUST slide protractor to the RIGHT to place mark

MUST BE PRECISE

STEP 1. Locate 2 points:• POS 1- EG1350 8009 and • POS 2- EG1610 8055 on the map.

EG 1350 8009

POS 1.50

TENINO Map SheetPoint #1

80.0

9

13

1. Read RIGHT

POS 1

STEP 1. Locate two points:• POS 1- EG13508009 and • POS 2- EG1610 8055 on the map.

POS 2

EG 1610 8055

TENINO Map Sheet; Point #2

80.10

.55

1. Read RIGHT

STEP 2. • Connect the points with a straight edge. • Draw a line extending beyond the points.

POS 2

POS 1

Use a STRAIGHT EDGE

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.

STEP 4. Read the angle value on the grid scale.

POS 2

POS 1 80 degrees1420 mils

Map Reading III

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

BACK AZIMUTH

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; Declination Diagrams

What is the GM Angle for Tenino? What is the GM Angle for Columbus?

Map Reading III

Practical ExerciseQuestion #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

MAGNETIC AZIMUTH: 275 DEGREES

WESTERLY G-M ANGLE: + 21 DEGREES

GRID AZIMUTH: 296 DEGREES

Answer: # 1

BONUS:

GRID AZIMUTH: 296 DEGREES

OPPOSITE DIRECTION: - 180 DEGREES

BACK AZIMUTH: 116 DEGREES

Map Reading III

Practical ExerciseQuestion #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

GRID AZIMUTH: 179 DEGREES

EASTERLY G-M ANGLE: -21 DEGREES

MAGNETIC AZIMUTH: 158 DEGREES

Answer: # 2

BONUS:

MAGNETIC AZIMUTH: 158 DEGREES

OPPOSITE DIRECTION: +180 DEGREES

BACK AZIMUTH: 338 DEGREES

Map Reading III

Practical ExerciseQuestion #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

Purpose North Types of

Azimuths Measuring

Azimuths

Plotting Azimuths

Practical Exercise

Map Reading III

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 II

Map Reading III Reading a Grid &

Determining Direction

GRC JROTCCOL. ALEXANDER