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MAP READING �AND �LAND NAVIGATION

FM 21-26

References: STP 21-1-SMCT, TC 3-25.26

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Task: 071-COM-1003 �Determine a Magnetic Azimuth Using a�Lensatic Compass

Conditions: You are a member of a squad or team in a field environment and have been directed to determine a magnetic azimuth. You have a compass and a designated point on the ground. Some iterations of this task should be performed in MOPP 4.

Standards: Inspect the compass. Determine the correct magnetic azimuth to the designated point within three degrees using the compass-to-cheek method, and within 10 degrees using the center-hold method.

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Compass-to-Cheek Method

Open the cover to a 90-degree angle to the base.
Position the eyepiece at a 45-degree angle to the base.
Place your thumb through the thumb loop.
Establish a steady base with your third and fourth fingers.
Extend your index finger along the side of the compass base.
Align the sighting slot of the eyepiece with the sighting wire (in the cover) on the designated point.
Read the azimuth under the index line

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Center Hold Method

a. Open the compass so that the cover forms a straight edge with the

base.

b. Position the eyepiece lens to the full upright position.

c. Place your thumb through the loop.

d. Establish a steady base with your third and fourth fingers.

e. Extend your index finger along the side of the compass.

f. Place the thumb of your other hand between the eyepiece and lens.

g. Extend the index finger along the remaining side of the compass.

h. Secure the remaining fingers around the fingers of the other hand.

i. Place your elbows firmly into your side.

j. Turn your entire body toward the designated point.

k. Align the compass to point directly at the designated point.

l. Read the azimuth from beneath the fixed black index line.

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Performance Measures

Inspect the compass.
Ensure there are no metal objects or electrical sources nearby.
Determine an azimuth using the compass-to-cheek method.
Determine an azimuth using the center-hold method.

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Task: 071-COM-0017 �Compute Back Azimuths

Conditions: You are a member of a squad or team that is preparing for a mission and you have been directed to determine back azimuth(s) for given azimuth(s). The azimuths may be in either degrees or mils. Some iterations of this task should be performed in MOPP 4.

Standards: Determine the back azimuth for each given azimuth to the exact degree or mil.

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Determine Back Azimuth in Degrees

Add 180 degrees if the azimuth is 180 degrees or less.

OR

Subtract 180 degrees if the azimuth is 180 degrees or more

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Determine Back Azimuth in Mils

If the azimuth is less than 3200 mils, add 3200 mils

OR

If the azimuth is more than 3200 mils, subtract 3200 mils.

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Performance Measures

Determine back azimuth using degrees.

Determine back azimuth using mils.

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Task: 071-COM-1012 �Orient a Map to the Ground by�Map-Terrain Association

Conditions: You are a member of a squad or team that is conducting movement in a field environment and you have been directed to orient a standard 1:50,000 scale military map to the ground. You do not have an operational compass. Some iterations of this task should be performed in MOPP 4.

Standards: Hold the map horizontally and match terrain features appearing on the map with physical features on the ground. Orient the map to within 30 degrees of magnetic north.

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Performance Measures

Hold the map in a horizontal position.
Match terrain features appearing on map with physical features on the ground.
Align the map with the terrain features on the ground to within 30 degrees of magnetic north.

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Task: 071-COM-1011 �Orient a Map Using a Lensatic Compass

Conditions: You are a member of a squad or team in a field environment and have been directed to orient a map in preparation for movement. You have a1:50,000-scale topographic map of the area and a compass. Some iterations of this task should be performed in MOPP 4.

Standards: Lay the map in a horizontal position, determine the direction and value of declination, and orient the map to the ground using a compass.

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A MAP IS ORIENTED WHEN IT IS IN A HORIZONTAL POSITION WITH ITS NORTH/SOUTH CORESPONDING TO

THE NORTH/ SOUTH

ON THE GROUND

Orienting the Map

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Steps to Orient a Map

Take the straightedge on the left side of the compass and place it alongside the north-south grid line with the cover of the compass pointing toward the top of the map.
Keep the compass aligned as directed above while rotating the map and compass together until the magnetic arrow is below the fixed black index line on the compass. Note: At this time, the map is close to being oriented.

3. Rotate the map and compass in the direction indicated by the declination diagram.

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Verify GM-Angles Are Correct

If the magnetic north arrow on the map is to the left of the grid north, check the compass reading to see if it equals the G-M angle given in the declination diagram

If the magnetic north is to the right of grid north, check the compass reading to see if it equals 360 degrees minus the G-M angle

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Performance Measures

Lay the map in a horizontal position.
Determine the direction of the declination and its value from the declination diagram.
Orient the map.

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Task: 071-COM-1000

Identify the Marginal information and Symbols on a Military Map

Conditions: You are a member of a squad or team in a field environment and have been given; a 1:50,000 scale military map and a requirement to identify the marginal information and symbols on the map. Some iterations of this task should be performed in MOPP 4.

Standard: Identify the basic colors, topographic symbols, and marginal information on a military map.

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Marginal Information

Sheet Name (1).

Sheet Number (2).

Series Name (3).

Scale (4).

Series Number (5).

Edition Number (6).

Index to Boundaries (7).

Adjoining Sheets Diagram (8).

Elevation Guide (9).

Declination Diagram (10).

Bar Scales (11).

Contour Interval Note (12).

Spheroid Note (13).

Grid Note (14).

Projection Note (15).

Vertical Datum Note (16).

Horizontal Datum Note (17).

Control Note (18).

Preparation Note (19).

Grid Reference Box (21).

Unit imprint and Symbol (22).

Legend (23).

Special Notes (24)

User’s Note (25)

Stock Number (26)

Conversion Graph (27)

https://550cord.com/land-navigation-training-fm-3-25-26/map-reading-land-navigation-ch3/#fig3-1

https://www.armywriter.com/board/references/TC3-25x26-Part1.pdf

a. Sheet Name (1). The sheet name is found in bold print at the center of the top and in the lower left area of the map margin. A map is generally named for the settlement contained within the area covered by the sheet, or for the largest natural feature located within the area at the time the map was drawn.

b. Sheet Number (2). The sheet number is found in bold print in both the upper right and lower left areas of the margin, and in the center box of the adjoining sheets diagram, which is found in the lower right margin. It is used as a reference number to link specific maps to overlays, operations orders, and plans. For maps at 1:100,000 scale and larger, sheet numbers are based on an arbitrary system that makes possible the ready orientation of maps at scales of 1:100,000, 1:50,000, and 1:25,000.

c. Series Name (3). The map series name is found in the same bold print as the sheet number in the upper left corner of the margin. The name given to the series is generally that of a major political subdivision, such as a state within the United States or a European nation. A map series usually includes a group of similar maps at the same scale and on the same sheet lines or format designed to cover a particular geographic area. It may also be a group of maps that serve a common purpose, such as the military city maps.

d. Scale (4). The scale is found both in the upper left margin after the series name, and in the center of the lower margin. The scale note is a representative fraction that gives the ratio of a map distance to the corresponding distance on the earth’s surface. For example, the scale note 1:50,000 indicates that one unit of measure on the map equals 50,000 units of the same measure on the ground.

e. Series Number (5). The series number is found in both the upper right margin and the lower left margin. It is a sequence reference expressed either as a four-digit numeral (1125) or as a letter, followed by a three- or four-digit numeral (M661; T7110).

f. Edition Number (6). The edition number is found in bold print in the upper right area of the top margin and the lower left area of the bottom margin. Editions are numbered consecutively; therefore, if you have more than one edition, the highest numbered sheet is the most recent. Most military maps are now published by the DMA, but older editions of maps may have been produced by the US Army Map Service. Still others may have been drawn, at least in part, by the US Army Corps of Engineers, the US Geological Survey, or other agencies affiliated or not with the United States or allied governments. The credit line, telling who produced the map, is just above the legend. The map information date is found immediately below the word “LEGEND” in the lower left margin of the map. This date is important when determining how accurately the map data might be expected to match what you will encounter on the ground.

g. Index to Boundaries (7). The index to boundaries diagram appears in the lower or right margin of all sheets. This diagram, which is a miniature of the map, shows the boundaries that occur within the map area, such as county lines and state boundaries.

h. Adjoining Sheets Diagram (8). Maps at all standard scales contain a diagram that illustrates the adjoining sheets. On maps at 1:100,000 and larger scales and at 1:1,000,000 scale, the diagram is called the index to adjoining sheets. It consists of as many rectangles representing adjoining sheets as are necessary to surround the rectangle that represents the sheet under consideration. The diagram usually contains nine rectangles, but the number may vary depending on the locations of the adjoining sheets. All represented sheets are identified by their sheet numbers. Sheets of an adjoining series, whether published or planned, that are at the same scale are represented by dashed lines. The series number of the adjoining series is indicated along the appropriate side of the division line between the series.

i. Elevation Guide (9). This is normally found in the lower right margin. It is a miniature characterization of the terrain shown. The terrain is represented by bands of elevation, spot elevations, and major drainage features. The elevation guide provides the map reader with a means of rapid recognition of major landforms.

j. Declination Diagram (10). This is located in the lower margin of large-scale maps and indicates the angular relationships of true north, grid north, and magnetic north. On maps at 1:250,000 scale, this information is expressed as a note in the lower margin. In recent edition maps, there is a note indicating the conversion of azimuths from grid to magnetic and from magnetic to grid next to the declination diagram.

k. Bar Scales (11). These are located in the center of the lower margin. They are rulers used to convert map distance to ground distance. Maps have three or more bar scales, each in a different unit of measure. Care should be exercised when using the scales, especially in the selection of the unit of measure that is needed.

l. Contour Interval Note (12). This note is found in the center of the lower margin normally below the bar scales. It states the vertical distance between adjacent contour lines of the map. When supplementary contours are used, the interval is indicated. In recent edition maps, the contour interval is given in meters instead of feet.

m. Spheroid Note (13). This note is located in the center of the lower margin. Spheriods (ellipsoids) have specific parameters that define the X Y Z axis of the earth. The spheriod is an integral part of the datum.

n. Grid Note (14). This note is located in the center of the lower margin. It gives information pertaining to the grid system used and the interval between grid lines, and it identifies the UTM grid zone number.

o. Projection Note (15). The projection system is the framework of the map. For military maps, this framework is of the conformal type; that is, small areas of the surface of the earth retain their true shapes on the projection; measured angles closely approximate true values; and the scale factor is the same in all directions from a point. The projection note is located in the center of the lower margin. Refer to DMA for the development characteristics of the conformal-type projection systems.

(1) Between 80° south and 84° north, maps at scales larger than 1:500,000 are based on the transverse Mercator projection. The note reads TRANSVERSE MERCATOR PROJECTION.

(2) Between 80° south and 84° north, maps at 1:1,000,000 scale and smaller are based on standard parallels of the lambert conformal conic projection. The note reads, for example, LAMBERT CONFORMAL CONIC PROJECTIONS 36° 40’ N AND 39° 20’ N.

(3) Maps of the polar regions (south of 80° south and north of 84° north) at 1:1,000,000 and larger scales are based on the polar stereographic projection. The note reads POLAR STEREOGRAPHIC PROJECTION.

p. Vertical Datum Note (16). This note is located in the center of the lower margin. The vertical datum or vertical-control datum is defined as any level surface (for example, mean sea level) taken as a surface of reference from which to determine elevations. In the United States, Canada, and Europe, the vertical datum refers to the mean sea level surface. However, in parts of Asia and Africa, the vertical-control datum may vary locally and is based on an assumed elevation that has no connection to any sea level surface. Map readers should habitually check the vertical datum note on maps, particularly if the map is used for low-level aircraft navigation, naval gunfire support, or missile target acquisition.

q. Horizontal Datum Note (17). This note is located in the center of the lower margin. The horizontal datum or horizontal-control datum is defined as a geodetic reference point (of which five quantities are known: latitude, longitude, azimuth of a line from this point, and two constants, which are the parameters of reference ellipsoid). These are the basis for horizontal-control surveys. The horizontal-control datum may extend over a continent or be limited to a small local area. Maps and charts produced by DMA are produced on 32 different horizontal-control data. Map readers should habitually check the horizontal datum note on every map or chart, especially adjacent map sheets. This is to ensure the products are based on the same horizontal datum. If products are based on different horizontal-control data, coordinate transformations to a common datum must be performed. UTM coordinates from the same point computed on different data may differ as much as 900 meters.

r. Control Note (18). This note is located in the center of the lower margin. It indicates the special agencies involved in the control of the technical aspects of all the information that is disseminated on the map.

s. Preparation Note (19). This note is located in the center of the lower margin. It indicates the agency responsible for preparing the map.

t. Printing Note (20). This note is also located in the center of the lower margin. It indicates the agency responsible for printing the map and the date the map was printed. The printing data should not be used to determine when the map information was obtained.

u. Grid Reference Box (21). This box is normally located in the center of the lower margin. It contains instructions for composing a grid reference.

v. Unit imprint and Symbol (22). The unit imprint and symbol is on the left side of the lower margin. It identifies the agency that prepared and printed the map with its respective symbol. This information is important to the map user in evaluating the reliability of the map.

w. Legend (23). The legend is located in the lower left margin. It illustrates and identifies the topographic symbols used to depict some of the more prominent features on the map. The symbols are not always the same on every map. Always refer to the legend to avoid errors when reading a map.

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MAP SCALES

LARGE: 1:50,000

MEDIUM: 1: 100,000

SMALL: 1: 250,000

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RED: POPULATED AREAS, MAIN ROADS AND BOUNDARIES

ON OLDER MAPS.

COLORS OF THE MAP

BLACK: MAN-MADE FEATURES, SUCH AS

BUILDINGS AND ROADS.

BROWN: RELIEF FEATURES & ELEVATION

(CONTOUR LINES ON OLDER MAPS).

GREEN: VEGETATION (WOODS, ORCHARDS, VEGITATION).

BLUE: WATER (PONDS, LAKES, RIVERS)

RED-BROWN: RELIEF FEATURES AND ELEVATION

(CONTOUR LINES ON RED-LIGHT READABLE MAPS).

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TOPOGRAPHIC SYMBOLS Man Made (BLACK)

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TOPOGRAPHIC SYMBOLS

Main Roads, Populated Areas, Boundaries (RED)

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TOPOGRAPHIC SYMBOLS Contour Lines (BROWN)

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TOPOGRAPHIC SYMBOLS

Drainage (BLUE)

�

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Performance Measures

Identify the six basic colors on a military map.
Identify symbols on a military map.
Identify the marginal information on a military map.

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TASK: 071-COM-1001 �Identify Terrain Features on a Map.

Conditions: You are a member of a squad or team in a field environment and have been directed to identify the terrain features on a map. You have been given a 1:50,000 scale military map.

Standards: Identify the five major, three minor, and two supplementary terrain features on a military map.

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CONTOUR LINES

Intermediate: Are contour lines located between two index lines.

ELEVATION IN METERS

Three types of contour lines

Supplementary: Are contour lines placed to specify half of

the contour interval.

Index: Are major elevation points and have the

elevation number written withing the contour.

(ex.100m,200m,300m)

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Five Major

Three Minor

Two Supplementary

Hidden Valley Ranch Salad Dressing

Hilltop, Valley, Ridge, Saddle, Depression

Draw, Spur, Cliff

Cut, Fill

TERRAIN FEATURES

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HILL: AN AREA OF HIGH GROUND. FROM

A HILLTOP, THE GROUND SLOPE DOWN IN

ALL DIRECTIONS.

FM 21-26: PAGE 10-9 (FIGURE 10-17)

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VALLEY: A STRETCHED-OUT GROOVE IN

THE LAND, USUALLY FORMED BY

STREAMS OR RIVERS.

FM 21-26: PAGE 10-10 (FIGURE 10-19)

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RIDGE: A SLOPING LINE OF HIGH GROUND.

FM 21-26: PAGE 10-11 (FIGURE 10-20)

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SADDLE: A DIP OR LOW POINT BETWEEN

TWO AREAS OF HIGHER GROUND.

FM 21-26 PAGE 10-11 (FIGURE 10-18)

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DEPRESSION: A LOW POINT IN THE GROUND

OR SINKHOLE. THEY ARE REPRESENTED BY CLOSE

CONTOUR LINES THAT HAVE TICK MARKS POINTING

TOWARD LOW GROUND.

FM 21-26: PAGE 10-11 (FIGURE 10-21)

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DRAW: A LESS DEVELOPED STREAM COURSE THAN A VALLEY.

THERE IS ESSENTIALLY NO LEVEL GROUND AND, THEREFORE,

LITTLE OR NO MANEUVER ROOM WITHIN ITS CONFINES.

FM 21-26: PAGE 10-12 (FIGURE 10-22)

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SPUR: A SHORT, CONTINUOUS SLOPING LINE OF

HIGHER GROUND, NORMALLY JUTTING OUT FROM

THE SIDE OF A RIDGE.

FM 21-26: PAGE 10-12 (FIGURE 10-23)

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CLIFF: A VERTICAL OR NEAR VERTICAL FEATURE; IT IS AN ABRUPT

CHANGE OF THE LAND. THE SLOPE IS SO STEEP THAT THE

CONTOUR LINES CONVERGE INTO ONE CONTOUR LINE OR THE LAST

CONTOUR LINE HAS TICK MARKS POINTING TO LOW GROUND.

FM 21-26: PAGE 10-13 (FIGURE 10-24A & B)

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CUT: A MAN-MADE FEATURE RESULTIING FROM CUTTING

THROUGH RAISED GROUND, USUALLY TO FORM A LEVEL BED

FOR A ROAD OR RAILROAD TRACK.

FILL: A MAN-MADE FEATURE RESULTING FROM FILLING A LOW

AREA, USUALLY TO FORM A LEVEL BED FOR A ROAD OR RAIL-

ROAD TRACK.

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STP21-1-SMCT PAGE 30 -31 (FIGURE4-5)

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Performance Measures

Identify the five major terrain features.
Identify the three minor terrain features.
Identify the two supplementary terrain features.

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TASK: 071-COM-1002 �Determine the Grid Coordinates of a Point on a Military Map

Conditions: You are a member of a squad or team in a field environment and have been directed to identify the grid coordinates of a point on a map. You have a 1:50,000 scale military map, a coordinate scale and protractor or plotting scale, a pencil, and paper. You have been shown the point on the map. Some iterations of this task should be performed in MOPP 4.

Standards: Determine the six-digit grid coordinates of the point identified on the map by: finding the coordinates of the grid square where the point is located and the four-digit grid coordinates of the point, with or without a coordinate scale and protractor or plotting scale. Include the 100,000 meter square identifier with the grid coordinate.

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GRID COORDINATES

Location Within 1000m

Four Digit Coordinate

To locate any coordinate:

Must go RIGHT then UP

(RP5904)

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GRID PRECISION

Six Digit Coordinates

Locate a point within

100 meters

Eight Digit Coordinates

Locate a point within

10 meters

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MILITARY PROTRACTOR

DEGREES

MILS

BASE LINE

INDEX

THE GTA 5-2-12 IS THE MOST

COMMONLY USED PROTRACTOR

FOR MAP READING.

FM 21-26: PAGE 6-4 & 6-5

(FIGURE 6-6 & 6-7)

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RP59850432

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Performance Measures

Determine the coordinates of the grid square.
Determine point grid coordinates.
Added the two letter 100,000 meter square identifier to the determined grid coordinate.

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TASK: 071-COM-1018 �Determine Azimuth Using a Protractor

Conditions: You are a member of a squad or team that has received an order requiring movement. You have been directed to determine the grid azimuth from the starting point and ending point designated in the order. You have a 1:50,000-scale military map, a military protractor (GTA 05-02-012), a pencil, and paper. Some iterations of this task should be performed in MOPP 4.

Standards: Identify the starting point and ending point on the map, draw a straight line on the map connecting the points, align the protractor to the map, and determine the value of the angle.

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Performance Measures

Identify the starting point on the map.
Identify the ending point on the map.
Draw a straight line on the map connecting the two points.
Align the protractor to the map
Determine the value of the angle.

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Task: 071-COM-1016 �Convert an Azimuth

Conditions: You are a member of a squad preparing to conduct tactical movement and you have been directed to convert azimuths in preparation for the movement. You have been given a 1:50,000 military map with a declination diagram, pencil, paper, a magnetic azimuth, and a grid azimuth. Some iterations of this task should be performed in MOPP 4.

Standards: Convert an azimuth into a back azimuth, a magnetic azimuth to a grid azimuth and a grid azimuth to a magnetic azimuth, without error

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Back Azimuth Recap

Add 180 degrees if the azimuth is 180 degrees or less.

Subtract 180 degrees if the azimuth is 180 degrees or more.

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Convert a Magnetic Azimuth to a Grid Azimuth

To convert a magnetic azimuth to grid azimuth, add or subtract the G-M angle.

Add if easterly G-M Angle

Subtract if westerly G-M Angle

As an example, given a magnetic azimuth of 190 degrees, using the diagram, you would add 9.5 degrees to 190 degrees to obtain a grid azimuth of 199.5 degrees.

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Convert a Grid Azimuth to a Magnetic Azimuth

To convert a grid azimuth to magnetic azimuth, add or subtract the G-M angle.

SUBTRACT if EASTERLY G-M Angle

ADD if WESTERLY G-M Angle

As an example, given a grid azimuth of 199.5 degrees, using the diagram, you would subtract 9.5 degrees from 199.5 degrees to obtain a magnetic azimuth of 190 degrees.

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Performance Measures

Convert an azimuth into a back azimuth
Convert a magnetic azimuth to a grid azimuth.
Convert a grid azimuth to magnetic azimuth.

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Task: 071-COM-1008 �Measure Distance on a Map

Conditions: Given a standard 1:50,000-scale military map, a strip of paper with a straight edge, and a pencil.

�Standards: Determine the straight-line distance between two points in meters with no more than 5 percent error. Determine the road (curved line) distance between two points in meters with no more than 10 percent error.�

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Measuring Distance

For map distances less than or equal to 1 inch—

(1) Line up the straight edge of a strip of paper with the beginning

and ending points on the map.

(2) Mark on the straight edge of the paper the beginning and ending

Points

(3) Match the marks on the paper with the appropriate bar scale

(4) Determine the distance on the scale that compares to the distance

on the paper.

For map distances greater than 1 inch—

(1) Line up the straight edge of a strip of paper with the beginning

and ending points on the map.

(2) Mark the beginning and ending points on the straight edge of the

paper.

(3) Place the starting point on the paper under the zero on the bar

scale.

(4) Measure off 4,000 meters and place a new tick mark on the paper.

(5) Place the new tick mark under the zero on the bar scale.

(6) Determine if the end point falls within the bar scale.

(a) Record the value on the scale of the end point, if the end

point fits on the scale.

(b) Add 4,000 meters to this value (a) to get the total difference.

(7) Determine if the end point falls outside the bar.

(a) Repeat steps 2b(4) and (5) until the end point falls within the

bar.

(b) Add 4,000 meters to the value you derived in step 2b(6)(a)

for each time you performed step 2b(4). This is the total difference.

�

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Measuring Distance

Convert a road map distance to miles, meters, or yards using the map's bar

scale. This is the actual distance you have to travel to reach the point form the

straight-line distance you identified in step 2.

a. Line up the straight edge of a strip of paper with the beginning point

and the point where the road makes the first curve on the map.

b. Mark on the straight edge of the paper the beginning and curve points.

c. Repeat steps 3a and b, each time using the point of the curve as the

next beginning point, until you reach the end point.

d. Use this step (3) to determine the road distance in miles, meters, or

yards as appropriate.

(1) If the total distance measured on the paper is less than or equal to

1 inch, use steps 2a(3) and (4).

(2) If the total distance measured on the paper is more than 1 inch, use

steps 2b(3) through (7).

�

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Performance Measures

Identify the graphic bar scale of the map.
Determine the straight-line distance between two points on a map.
Measure the distance along a road, stream, or other curved line.

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Any Questions?