Map Reading IV
Determining Direction
GRC JROTC
COL(R) Alexander
Outline
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Purpose
Polar Coordinates & Practical Exercise
Intersection & Practical Exercise
Resection & Practical Exercise
Summary
Conclusion
Polar Coordinates
1. Plot an azimuth from a known point.
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EG 1290 8018
2. Plot the distance from the known point
along the azimuth line.
•
56 degrees
3. The Polar Coordinate is at the end of the
azimuth/distance line.
•
3400 M
Tenino Map
STEP 1: PLACE THE INDEX MARK OF THE PROTRACTOR AT THE
CENTER OF MASS ON THE POINT FROM WHICH YOU ARE
MEASURING.
ENSURE your
protractor is straight
UP & DOWN !
POINT 1
EG 1290 8018
Tenino Map
STEP 2: LOCATE THE DESIRED AZIMUTH ON THE PROTRACTOR
SCALE AND PLACE A DOT ON THE MAP AT THIS AZIMUTH.
56
PNT 1
EXAMPLE: 56 DEGREES
STEP 3: REMOVE THE PROTRACTOR AND CONNECT THE POINT
AND DOT WITH A STRAIGHT LINE.
PNT 1
STEP 3:
3. REMOVE
REMOVETHE
THEPROTRACTOR
PROTRACTORAND
ANDCONNECT
CONNECTTHE
THEPOINT
POINT
AND DOT WITH A STRAIGHT LINE.
56o
PNT 1
STEP 4: SELECT THE APPROPRIATE SCALE MEASUREMENT AND
PLACE A PAPER STRAIGHT EDGE ON THE SCALE.
EXAMPLE: DISTANCE IN METERS
Piece of white paper
STEP 5: DETERMINE THE DESIRED DISTANCE TO MEASURE FROM
THE SCALE AND MARK THE PAPER AT THIS DISTANCE USING TICK
MARKS.
EXAMPLE: 3400 METERS (3000 + 400)
3400 M
100
100
100
100
100
100
Each alternating block is 100 Meters
STEP 6: ALIGN THE STRAIGHT EDGE WITH THE AZIMUTH LINE.
ENSURE THE FIRST TICK MARK IS CENTER MAST
ON THE KNOWN POINT.
PNT 1
STEP 4: PLACE A DOT ON THE MAP AT THE SECOND TICK MARK
FROM THE STRAIGHT EDGE ON THE MAP.
THE POSITION OF THE SECOND TICK MARK
IS THE POSITON OF THE UNKNOWN POINT.
PNT 1
USE Protractor !
1 _____
3 _____
5 _____
5
_____
8
_____
GRID SQUARE
8 _____
5 _____
5
_____
REMOVE THE STRAIGHT EDGE AND DETERMINE THE GRID
COORDINATE TO THE SECOND POINT.
56o
Read the
Grid:
EG 1575 8205
PNT 1
Practical Exercise (ANSWERS)
1. QUESTION: What are the polar coordinates plotted from the center of the
Reservoir at EG 04609945 at a grid azimuth of 158 degrees and a distance of
1700 meters? Describe this location?
• EG 0525 9790 (road intersection next to a Pit)
2. QUESTION: What are the polar coordinates plotted from the water
tower in grid square EG1185 at a grid azimuth of 30 degrees and a
distance of 3500 meters? Describe the terrain feature located here?
• EG 1325 8860 (spur)
3. QUESTION: What are the polar coordinates plotted from the
Deschutes fire tower in grid square EG 1795 at a grid azimuth of 303
degrees and a distance of 2600 meters? Describe the terrain feature
located here?
• EG 1550 9660 (saddle)
Intersection
(determining the location of an object/point)
1. Determine the position (GRID LOCATION) of an
unknown point (or object) by occupying at least two
(2), but preferably three (3) known locations.
2. Determine the azimuth (magnetic-compass) to the
unknown point from these locations
3. Plot the azimuths (grid-map) from the positions to
locate the to the unknown point by their intersections
on the map.
STEP 1: SIGHT THE UNKNOWN POINT (or OBJECT) ON
THE GROUND.
STEP 2: LOCATE YOUR POSITION ON THE GROUND
AND MARK IT ON THE MAP.
?
You must be able to
accurately locate (a GRID)
your POSITION !
POS 1
STEP 2. LOCATE YOUR POSITION ON THE GROUND
AND MARK IT ON THE MAP.
EXAMPLE: ROAD JUCTION AT EG13508009
POS 1
You must be able to
accurately locate your
POSITION !
STEP 3. DETERMINE THE MAGNETIC AZIMUTH FROM THE
ROAD JUNCTION TO THE ENEMY POSITION (with a
COMPASS).
POS 1
BUT WAIT ! WHAT DO YOU
HAVE TO DO WITH THAT
COMPASS AZIMUTH BEFORE
YOU CAN USE IT ON A MAP?
POS 1
STEP 4: CONVERT THE MAGNETIC AZIMUTH
TO A GRID (map) AZIMUTH.
MAGNETIC AZIMUTH:
59 DEGREES
EASTERLY G-M ANGLE:
+21 DEGREES
GRID AZIMUTH:
80 DEGREES
Tenino Map
STEP 5: DRAW A LINE FROM THE ROAD JUNCTION
ALONG THE 80 DEGREE GRID AZIMUTH.
80
POS 1
STEP 6: MOVE TO (or contact someone else who can
provide a magnetic azimuth) A SECOND POSITION
WHERE THE UNKNOWN POINT/OBJECT CAN BE SEEN
AND OBTAIN ANOTHER COMPASS AZIMUTH TO THE
OBJECT AND MARK THE AZIMUTH ON THE MAP.
POS 1
POS 2
STEP 6: MOVE TO (or contact someone else who can
provide a magnetic azimuth) A SECOND POSITION
WHERE THE UNKNOWN POINT/OBJECT CAN BE SEEN
AND OBTAIN ANOTHER COMPASS AZIMUTH TO THE
OBJECT AND MARK THE AZIMUTH ON THE MAP..
EXAMPLE: ROAD JUCTION AT EG13318108
POS 2
POS 1
STEP 7: DETERMINE THE MAGNETIC AZIMUTH FROM
THE SECOND ROAD JUNCTION TO THE OBJECT /
POSITION.
POS 1
POS 2
BUT WAIT ! WHAT DO YOU
HAVE TO DO WITH THAT
COMPASS AZIMUTH BEFORE
YOU CAN USE IT ON A MAP?
POS 1
POS 2
STEP 4: CONVERT THE MAGNETIC AZIMUTH
TO A GRID AZIMUTH.
MAGNETIC AZIMUTH:
79 DEGREES
EASTERLY G-M ANGLE:
+21 DEGREES
GRID AZIMUTH:
100 DEGREES
STEP 9. DRAW A LINE FROM THE SECOND ROAD
JUNCTION ALONG THE 100 DEGREE GRID AZIMUTH.
POS 1
100
POS 2
STEP 10: WHERE THE LINES CROSS IS THE LOCATION
OF THE UNKNOWN POINT or OBJECT (enemy tank).
POS 2
POS 1
EG16208055
IT’S DESIRABLE TO REPEAT THE PROCEDURE FROM A
THIRD POINT TO INCREASE THE ACCURACY.
EXAMPLE: ROAD JUNCTION AT EG15478180
POS 3
POS 2
POS 1
MAGNETIC AZIMUTH:
128 DEGREES
EASTERLY G-M ANGLE: +21 DEGREES
GRID AZIMUTH:
149 DEGREES
POS 3
POS 2
POS 1
NOTICE THAT THE LINES FROM THE FIRST AND SECOND
POINT FORM A SHALLOW ANGLE.
THIS DECREASES ACCURACY. WHENEVER POSSIBLE,
CHOOSE LOCATIONS THAT WILL GIVE YOU A LARGER
ANGLE (CLOSER TO 90 DEGREES LIKE POSITION 3.)
NOTE: WHEN TRIANGULATING, THE CENTER OF
THE TRIANGLE IS RECORDED AS THE
LOCATION.
EG16208055
Practical Exercise
1 of 2
YOUR SQUAD OCCUPIES 2 OBSERVATION POSTS. THE
TEAM AT THE WATER TOWER IN GRID SQUARE EG 0985
SEES THE ENEMY AT A MAGNETIC AZIMUTH OF 351
DEGREES. THE SECOND TEAM, LOCATED AT THE WATER
TOWER IN GRID SQUARE EG 1185 SEES THE ENEMY AT A
MAGNETIC AZIMUTH OF 300 DEGREES.
QUESTION: WHAT IS THE GRID LOCATION OF THE ENEMY?
ANSWER: GRID COORDINATE EG 0979 8765
Practical Exercise
2 of 2
YOUR SQUAD IS OPERATING AS AN OBSERVATION TEAM & YOU
SEE SIX (6) ENEMY HELICOPTERS LAND & THEN DISAPPEAR FROM
YOUR SIGHT. PRIOR TO THE HELICOPTERS DISAPPEARING, YOU
SHOT A MAGNETIC AZIMUTH TO THE LOCATION WHERE YOU SAW
THEM LAND. THIS MAGNETIC AZIMUTH IS 316 1/2 DEGREES. YOUR
LOCATION IS THE BRIDGE IN GRID SQUARE EH 1000. YOU CONTACT
YOUR OTHER TEAM LOCATED IN THE ZION CHAPEL TOWER AT GRID
SQUARE EH 1102. THEY HAVE A SIGHTING OF SIX (6) ENEMY
HELICOPTERS AT A MAGNETIC AZIMUTH OF 229 1/2 DEGREES.
BOTH YOUR TEAMS PERFORM AN INTERSECTON.
QUESTION: WHAT IS THE GRID LOCATION AND THE TYPE OF
TERRAIN WHERE THE SIX (6) ENEMY HELICOPTERS LANDED?
ANSWER: GRID LOCATION EH 093022, DEPRESSION.
Resection
(determining YOUR location using known objects/points)
1. Determine the position of an unknown point
(YOU) by locating at least two (2), but preferably
three (3) known locations (points on the ground).
2. Determine the azimuth to the known points from
the unknown point/location.
3. Plot the back azimuths from the known points to
locate the unknown point by their intersections.
STEP 1: LOCATE A FEATURE OR OBJECT THAT IS
IDENTIFIABLE ON BOTH THE GROUND AND THE MAP
AND MARK THE MAP LOCATION.
EXAMPLE: TOWER LOCATED AT EG 1804 8759
“Where in the heck am I???”
EXAMPLE: TOWER LOCATED AT EG 1804 8759
KP 1
STEP 1: LOCATE A FEATURE OR OBJECT THAT IS
IDENTIFIABLE ON BOTH THE GROUND AND
THE MAP AND MARK THE MAP LOCATION.
STEP 2: MEASURE THE MAGNETIC AZIMUTH (w/ your
COMPASS) TO THE KNOWN POSITION (Tower) AND
CONVERT THE MAGNETIC AZIMUTH TO A GRID AZIMUTH.
STEP 2: MEASURE THE MAGNETIC AZIMUTH TO THE
KNOWN POSITION AND CONVERT THE MAGNETIC
AZIMUTH TO A GRID AZIMUTH.
MAGNETIC AZIMUTH:
29 DEGREES
EASTERLY G-M ANGLE:
+21 DEGREES
GRID AZIMUTH:
50 DEGREES
STEP 3. CHANGE THE GRID AZIMUTH TO A BACK
AZIMUTH & DRAW A LINE FROM THE KNOWN POSITION
(Tower) BACKWARD TOWARD YOUR UNKNOWN
POSITION.
GRID AZIMUTH:
50 DEGREES
ADD:
+180 DEGREES
GRID BACK AZIMUTH:
230 DEGREES
230
KP 1
STEP 3: CHANGE THE GRID AZIMUTH TO A BACK
AZIMUTH & DRAW A LINE FROM THE KNOWN POSITION
(Tower) BACKWARD TOWARD YOUR UNKNOWN
POSITION.
STEP 4: LOCATE A SECOND FEATURE OR OBJECT
THAT IS IDENTIFIABLE ON BOTH THE GROUND & THE
MAP AND MARK THE MAP LOCATION.
EXAMPLE: BRIDGE LOCATED AT EG 1500 8389
KP 1
EXAMPLE: BRIDGE LOCATED AT EG 1500 8389
KP 2
STEP 4: LOCATE A SECOND FEATURE OR OBJECT
THAT IS IDENTIFIABLE ON BOTH THE GROUND & THE
MAP AND MARK THE MAP LOCATION.
STEP 5: MEASURE THE MAGNETIC AZIMUTH (w/ your
Compass) TO THE SECOND KNOWN POSITION &
CONVERT THE MAGNETIC AZIMUTH TO A GRID AZIMUTH.
STEP 5: MEASURE THE MAGNETIC AZIMUTH TO THE
SECOND KNOWN POSITION & CONVERT THE MAGNETIC
AZIMUTH TO A GRID AZIMUTH.
MAGNETIC AZIMUTH:
151 DEGREES
EASTERLY G-M ANGLE:
+21 DEGREES
GRID AZIMUTH:
172 DEGREES
STEP 6: CHANGE THE GRID AZIMUTH TO A BACK
AZIMUTH & DRAW A LINE FROM THE SECOND KNOWN
POSITION BACKWARD TOWARD YOUR UNKNOWN
POSITION.
GRID AZIMUTH:
172 DEGREES
ADD:
180 DEGREES
GRID BACK AZIMUTH:
352 DEGREES
STEP 6. CHANGE THE GRID AZIMUTH TO A BACK
AZIMUTH AND DRAW A LINE FROM THE
SECOND KNOWN POSITION BACKWARD
TOWARD YOUR UNKNOWN POSITION. KP 1
352
KP 2
STEP 7: THE POINT WHERE THE 2 LINES INTERSECT IS
YOUR LOCATION.
KP 1
EG 1485 8494
KP 2
STEP 8: FOR A CHECK ON ACCURACY, YOU SHOULD
CONSTRUCT A THIRD LINE FOLLOWING THE
STEPS AS OUTLINED.
KP 1
KP 3
KP 2
WHENEVER POSSIBLE, CHOOSE LOCATIONS THAT WILL
GIVE YOU A LARGER ANGLE WHERE THE LINES
INTERSECT TO INCREASE ACCURACY.
Practical Exercise
1 of 2
WHILE ON A RECONNAISSANCE MISSION, AN ENEMY SCOUT PLATOON
DETECTS YOUR SQUAD. YOU TAKE UP A DEFENSIVE POSITION & DECIDE TO
REQUEST INDIRECT FIRE SUPPORT. YOU ARE NOT SURE OF YOUR
LOCTION. FROM YOUR LOCATION, YOU CAN SEE A LOOKOUT TOWER IN
GRID EG 1887 AT A MAGNETIC AZIMUTH OF 110 DEGREES & A TV RELAY
TOWER IN GRID EG1287 AT A MAGNETIC AZIMUTH OF 215 DEGREES.
QUESTION: WHAT IS YOUR LOCATION?
ANSWER: EG 155 897
YOU DETERMINE A DISTANCE OF 800 METERS TO THE ENEMY
WITH YOUR LASER RANGE FINDER AND A MAGNETIC AZIMUTH OF
290 DEGREES.
QUESTION: WHAT IS THE GRID LOCATION OF THE ENEMY SCOUT
PLATOON?
ANSWER: EG 149 902
Practical Exercise
2 of 2
QUESTION: YOU HAVE DETERMINED THAT THE MAGNETIC AZIMUTH FROM
YOUR POSITION TO THE TV RELAY TOWER IN GRID SQUARE EG1287 IS 3
DEGREES & THE MAGNETIC AZIMUTH TO THE SPOT ELEVATION 199 IN GRID
SQUARE EG 1385 IS 77 DEGREES. WHAT IS THE SIX DIGIT GRID
COORDINATE OF YOUR LOCATION?
ANSWER: EG 116856
QUESTION: THE MAGNETIC AZIMUTH FROM YOUR LOCATION TO THE
WATER TOWER AT EG093853 IS 63 DEGREES AND THE
MAGNETIC AZIMUTH TO THE WATER TOWER AT EG097827
IS 104 DEGREES. WHAT IS THE SIX DIGIT COORDINATE TO
YOUR LOCATION?
ANSWER: EG 063849
Summary
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Purpose
Polar Coordinates & Practical Exercise
Intersection & Practical Exercise
Resection & Practical Exercise
Summary
Conclusion
Conclusion
Advanced land navigations techniques such
as polar coordinates, intersection, and
resection are essential to navigating
successfully and accurately. Having theses
skills will help you fight, survive, and win
on the battlefield.