Operational Medicine 2001
Field Medical Service School
Student Handbook

LAND NAVIGATION
FMST 0205
03 Nov 99

TERMINAL LEARNING OBJECTIVES

1.  Given a combat environment (day and night), and individual combat equipment, navigate terrain using a map and compass per the reference.  (FMST.02.05)

ENABLING LEARNING OBJECTIVES

1.      Without the aid of reference materials, identify the nomenclature on the compass, per the student handout.  (FMST.02.05a)

2.      Without the aid of reference materials and given a map and compass, select the two methods of orienting the map, per the student handout.  (FMST.02.05b)

3.      Without the aid of reference materials, identify the five basic colors found on map, per the student handout.  (FMST.02.05c)

4.      With the aid of a military map, locate a point on the map from a six digit grid coordinate, per the reference.  (FMST.02.05d)

5.      Without the aid of reference materials, select the two methods to hold the compass, per the student handout.  (FMST.02.05e)

6.      Given a compass and map, while on the land navigation course, locate a point using the six digit grid coordinate, and determine a route on the course, per the student handout.  (FMST.02.05f)

OUTLINE

A.     Lensatic Compass DESCRIPTION.  The primary instrument used to determine and maintain direction during land navigation is the lensatic compass.  This compass provides the most reliable means of accurately maintaining direction while navigating from one point to another.  The name “lensatic compass” derives from the magnifying lens which is mounted in the eyepiece.  There are three major parts to the compass:  Cover, Base, and Lens

1.      Nomenclature 

a.       Graduated Straight Edge.  Formed by the case and cover when the compass is fully opened.  When used on a 1:50,000 map, each line of the scale represents 200 meters of ground distance.

b.      Thumb Loop.  Aids in keeping the compass level while shooting an azimuth.

c.       Lens.  Used to read the numbers on the floating dial.

d.      Sighting Slot.  Functions the same as the rear sight of a rifle.

e.       Sighting Wire.  Used in a similar fashion as the front sight of a rifle when shooting an azimuth.

f.        Luminous Sighting Dots.  Used in place of the sighting wire at night.

g.       North Seeking Arrow.  Points towards magnetic north.  This is a luminous arrow.

h.       Bezel Ring.  Enables you to follow an azimuth at night.  As the bezel ring is turned, the tip of a detent spring moves from notch to notch along the ring.  Each click is equal to a three degree change in direction.

i.         Index Line.  The azimuth you read will be directly under the index line.

j.        Short Luminous Line.  Used in conjunction with the index line and luminous arrow to follow an azimuth.

k.      Floating Dial.  Contains the degrees and mils.  Used for the direction in which you are pointing your compass.

  Figure 1.

B.     Compass Precautions.  Certain precautions regarding the care and use of a magnetic compass are important because they ensure, within reason, that a compass will work when needed.

1.      The dial has a delicate balance and a rough shock could damage it.

2.      WHEN NOT IN USE, CLOSE AND PUT THE COMPASS AWAY TO PROTECT IT

3.      Metal and electrical wires have an adverse effect on the operation of the lensatic compass.  Recommended safe distances from certain objects are:

a.       High-tension power lines.....…. 55 meters

b.      Field gun, truck, or tank....…... 10 meters

c.       Barbed wire, telephone wires... 10 meters

d.      Machinegun...................……...  2 meters

e.       Rifle........................…………… 0.5 meters

4.      Nonmagnetic metals and alloys do not effect compass readings.

C.     Methods to hold Compass.  There are two methods to hold a compass; Compass to cheek technique and the center hold method.

1.      Compass-to-Cheek Technique.  Fold the cover of the compass containing the sighting wire to a vertical position, and then fold the rear sight slightly forward.  Look through the rear-sight slot and align the front-sight hairline with the desired object in the distance.  Then glance down at the dial through the eye lens to read the azimuth.  Note:  The compass-to-cheek technique is used almost exclusively for sighting, and it is the best technique for this purpose.

NOTE:  Compass-to-cheek method will be utilized during the daytime.

2.      Center Hold Technique.  First, open the compass fully so that the cover forms a straight edge with the base.  Move the lens (rear sight) to the rearmost position, allowing the dial to float freely.  Next, place your thumb through the thumb loop, form a steady base with your third and fourth fingers, and extend your index finger along the side of the compass.  Place the thumb of the other hand between the lens (rear sight) and the bezel ring; extend the index finger along the remaining side of the compass, and the remaining fingers around the fingers of the other hand.  Pull your elbows firmly into your sides; this will place the compass between your chin and your belt.  To shoot an azimuth, simply turn your entire body toward the object, pointing the compass cover directly at the object.  Once you are pointing at the object, look down and read the azimuth from beneath the fixed black index line.

D.     Presetting A Compass And Following An Azimuth

1.      Daylight Hours or With a Light Source.

a.    Hold compass in the palm of the hand.

b.    Rotate yourself until the desired azimuth falls under the fixed black index line.

c.    Turn the bezel ring until the luminous line is aligned with the north-seeking arrow.  Once the alignment is obtained, the compass is preset.

2        To follow an azimuth, assume the center hold technique and turn your body until the north-seeking arrow is aligned with the luminous line.  Then proceed forward in the direction of the front covers sighting wire, which is aligned with the fixed black index line that contains the desired azimuth.

E.      Using the compass during limited visibility

1.      Rotate the bezel ring until the luminous line is over the fixed black line.

2.      Find the desired azimuth and divide it by 3.  The result is the number of clicks to rotate the bezel ring.

3.      Count the desired number of clicks.  If the desired azimuth is smaller than a 180 degrees, the number of clicks on the bezel ring should be counted in a counterclockwise direction.  For example, if the desired azimuth is 51 degrees, divide by 3, which equals 17 clicks counterclockwise.  If the desired azimuth is larger than 180 degrees, subtract the number of degrees from 360 and divide by 3 to obtain the number of clicks.  Count them in a clockwise direction.  For example, the desired azimuth is 330 degrees: 360 - 330 = 30¸ 30/3 = 10 clicks clockwise.

4.      With the compass preset as described, assume a center hold technique and rotate your body until the north seeking arrow is aligned with the luminous line on the bezel.  Then proceed forward in the direction you are facing or follow the direction the luminous dots which are aligned with the fixed black index line containing the azimuth.

F.      ORIENT THE MAP USING A COMPASS.  The first step for a navigator in the field is orienting the map.  A map is oriented when it is in a horizontal position with the north and south grid lines corresponding to the north and south on the ground.

1.      First Technique.

a.     Determine the direction of the declination and its value from the declination diagram. 

Figure 2.  Declination Diagram

2.      Second Technique.

a.     Determine the direction of the declination and its value from the declination diagram.

b.     Using any north south grid line on the map as a base, draw a magnetic azimuth equal to the GM angle given in the declination diagram with the protractor.

c.     If the declination is easterly (right), the drawn line is equal to the value of the GM angle.  Align the straight edge, which is on the left side of the compass, alongside the drawn line on the map.  Rotate the map and compass until the magnetic arrow of the compass is below the fixed black index line.  The map is now oriented.

d.     If the declination is westerly (left), the drawn line is equal to 360 degrees minus the value of the GM angle.  Align the straight edge, which is on the left side of the compass, alongside the drawn line on the map.  Rotate the map and compass until the magnetic arrow of the compass is below the fixed black index line.  The map is now oriented.

G.     DETERMINING AN AZIMUTH.  An azimuth is defined as a horizontal angle measured clockwise from a north base line.  This north base line could be true north, magnetic north, or grid north.  The azimuth is the most common military method of expressing direction.  When using an azimuth, the point from which the azimuth originates is the center of an imaginary circle.  This circle is divided into 360 degrees.

1.      Magnetic Azimuth.  Determined by using magnetic instruments, such as lensatic compass.  A magnetic azimuth comes from the compass.

2.      Grid Azimuth.  When an azimuth is plotted on a map between point A and point B, the points are joined together by a straight line.  A protractor is used to measure the angle between grid north and the drawn line.  This measured azimuth is the grid azimuth.  The grid azimuth comes from the map.

H.     Converting Azimuths.  As stated earlier, azimuths measured with a protractor are grid azimuths (measured from grid north) and azimuths determined with a compass are magnetic azimuths (measured from magnetic north).  Magnetic azimuths cannot be plotted on a map with a protractor unless they are converted to grid azimuths and vice versa.

1.      Convert Azimuths Using the LARS Rule.  This can be used to convert from magnetic to grid or from grid to magnetic.

A)  To determine the G-M angle for the map you are using, perform the following steps:

1)      Go to the declination diagram in the margin of your map.

2)      Place your finger on the north line that corresponds to the azimuth you have (grid or magnetic).

3)      Move your finger on the north line you are converting to (magnetic or grid).

4)      Apply the LARS (Left Add, Right Subtract) rule.  If your finger moved left, you would add the G-M angle to the beginning azimuth.  If your finger moved right, you would subtract the G-M angle from the beginning azimuth.

I.        LOCATE AN UNKNOWN POINT ON THE GROUND

1.      Resection.  Locating one’s position on the map by determining the grid azimuth to at least two well-defined locations that can be pinpointed on the map.  For greater accuracy, the desired method of resection will be to use three well-defined locations. Ensure they are at least 30 degrees apart.

a.       Orient the map with compass.

b.    Identify two or three known distant locations on the ground and mark them on the map.

c.     Measure the magnetic azimuth to the known position from your location using a compass.

Figure 4.

d.     Convert the magnetic azimuth to grid azimuth.

e.     Convert the grid azimuth to a back azimuth.  Using a protractor, scale the back azimuth on the map from known position back to your known position.

f.      Repeat 3, 4, and 5 for a second position and a third position if desired.

g.    Your location is the point where the lines cross.

Figure 5.

2.      Intersection.  Locating an unknown point by successively occupying at least two known points on the ground and then map sighting on the unknown location.  It is used to locate distant or inaccessible points or objects such as enemy targets, danger areas and so forth.

a.       Orient the map with compass.

b.     Locate and mark your position on the map.

c.     Determine the magnetic azimuth to the unknown position using the compass.

d.     Convert the magnetic azimuth to grid azimuth.

e.     Draw a line on the map from your position on this grid azimuth.

f.       Move to a second known point and repeat steps 1, 2, 3, 4, 5, and 6.  The location of the unknown position is where the lines cross on the map.  Again, the two positions must be at least 30 degrees apart.

J.       PACE COUNT.  Another way to measure ground distance is the pace count.  A pace is equal to one natural step, about 30 inches long.  To accurately use the pace count method, you must know how many paces it takes to walk 100 meters.  To determine this, you must walk an accurately measured course and count your number of paces.  A pace course can be as short as 100 meters or as long as 600 meters.  The pace course, regardless of length, must be on similar terrain to what you will be walking.  It does no good to walk a course on flat terrain and then try to use that pace count on hilly terrain.  To determine your pace count on a 600-meter course, count the paces it takes to walk the 600 meters, then divide the total paces by six.  The answer will give you the average paces it takes you to walk a 100 meters.  It is important that each person who navigates while dismounted knows his pace count.

1.      Keeping Track of Your Pace Count.

a.       Tie knots on a string.

b.     Place pebble in your pocket for every 100 meters.

c.     Place tick mark on a piece of paper or in a note book.

K.    Factors effectING pace count 

1.      Slopes.  Your Pace will lengthen on down slopes and shorten on upgrades.

2.      Winds.  A head wind shortens the pace and a tail wind increases it.

3.      Surfaces.  Sand, gravel, mud, snow, will shorten the pace.

4.      Elements.  Snow, rain, or ice will cause pace to shorten.

5.      Clothing.  Excess clothing and boots with poor traction affect the pace length.

6.      Visibility.  Poor visibility, such as fog, rain, or darkness will shorten the pace.

L.      STEERING MARKS 

1.      Steering marks should never be determined from a map study.  They are selected as the march progresses and are commonly on or near the highest points along the azimuth line you are following.  They may be uniquely shaped trees, rocks, hilltops, posts, towers, buildings, or anything that can be easily identified.  If you do not see a good steering mark to the front, you might use a back azimuth to some feature behind you until a good steering mark appears out in front.

2.      Dead reckoning without natural steering marks is used when the area through which you are traveling is devoid of features, or when visibility is poor.  At night, it may be necessary to send a member of the unit out in front of your position to create your own steering mark in order to proceed.  His position should be as far out as possible to reduce the number of chances for error as you move.  Hand and arm signals or a radio may be used in placing him on the correct azimuth.  After he has been properly located, move forward to his position and repeat the process until some steering marks can be identified or until you reach your objective.

M.   THE MAP. 

1.      Purpose.  Permit a person to visualize an area of the earth's surface with outstanding features properly positioned.

2.      Definition.  Reduced, or scale drawing of the ground and important things          on the ground as seen from the air:

a.       Shows us what an area looks like without actually being there. 

b.      A clear and handy reference tool

3.      Characteristics of a Map:

a.       Designed to show us common information.

b.      Location of ground objects.

c.       Populated areas.

d.      Routes of travel.

e.       Communication lines.

f.        Extent of vegetation cover.

g.       Elevation and relief of the earth's surface.

4.      Care and Importance.

a.       Maps are printed on paper and require protection from water, mud and tearing.  When you mark on your map, use lighter lines which are easily erased without smearing.  If trimming the map, be careful not to cut any of the marginal information:

1)      Grid data.

2)      Magnetic Declination Data.

3)      Overlapping Grid Values.

4)      Tick Marks.

b.      Maps must be protected because they can hold tactical information such as:

1)      Friendly positions.

2)      Friendly supply points.

3)      Patrol routes with call signs and frequencies.

4)      Control measures (phase lines).

N.    MAP ILLUSTRATION.        

1. Symbols:

a.       The mapmaker uses standard symbols.

b.      They represent natural and manmade features.

c.       Resemble as closely as possible, the actual features but as viewed from above.

2. Military Symbols.  Type of symbols are used as a method of showing identity, size and movement  of troops.  They are not represented on maps because units they represent are constantly moving and changing.  Security is also a consideration.

3. Map Colors.  To ease the identification of features on the map, the topographic symbols are usually printed in different colors, with each color identifying a class of features.  The colors vary with different types of maps, but on a standard, large scale, topographic map, there are five different colors.

a.       Black.  Used to identify the majority of cultural or man made features, such as buildings, bridges, and roads not shown in red.

b.      Red.  Main roads, built up areas, and special features such as dangerous or restricted areas.

c.       Blue.  Is for water features; lakes, rivers, swamps, and streams.

d.      Green.  Identifies vegetation such as woods and orchards.

e.       Red Brown.  All landforms: contours, fills, and cuts.

NOTE:  Occasionally other colors may be used to show special information.  These, as a rule, will be indicated in the margin of information.  Currently there are changes being made to the color system which may vary in the margin of information.

O.    MARGIN & LEGEND INFORMATION.

1. Margin of Information.  When using a map, the instructions are placed around the outer edges of the map and are known as margin of information.  All maps are not the same, so every time a different map is used one must examine the margin of information carefully.

2. Sheet Name.  Found in two places: The center of the upper margin and the lower right margin.

3. Sheet Number.  Found in the upper right hand margin.  Used as a reference number for the map sheet.

4. Series Name.  Found in the upper left margin.  A map series usually comprises a group of similar maps on the same scale.

5. The Scale Notation.  The scale note represents a fraction which gives the ration of the maps distance to the corresponding distance on the earth's surface.  Example:  Scale note 1:50,000 indicates that one unit of measurement on the map equals 50,000 inches on the ground.

6. Series Number.  Appears in the upper right margin and the lower left margin.  A comprehensive reference expressed either as a four-digit number or as a letter followed by three or four numbers.

7. Index Adjoining Sheets.  In the lower right hand corner is the index to adjoining sheets.  The diagram shows the sheet number of the adjacent areas.  The map sheet you are using is pictured in the center of the diagram.  The sheet number in the highlight square should be the same as the map sheet number you are using.

8. Bar Scales:

a.       Located at the center bottom of the margin, below the map face.

b.      Special "rulers", ground distance may be measured directly without having to convert the map scale ratio.

c.       Normally, the scale for meters, yards, statute miles (land) and nautical miles (sea)

d.      Easy to use, but notice that "zero" is not at the end of the scale.

Figure 6. 

9. Straight Line Distance.  To measure line distance between two points:

a.       Lay a straight strip of paper on the map so that the edge touches the center on both points.

b.      Make a tick mark on the edge of the paper at each point.

c.       Lay the paper strip along the scale that corresponds to the unit of measure you are working with.

d.      Place the right tick mark of the paper strip on the largest full unit on the primary scale (to the right of zero), allowing the remainder to fall on the extension of the scale (to the left of zero).

10. Curved or Irregular Distance.  To measure distance along a winding road, stream, or any other curved line:

a.       Make a tick mark near one end of the irregular line to be measured.

b.      Align the paper strip along the center of the first straight portion of the line.

c.       Make a tick mark at the other end of that portion on both the paper strip and the map.

d.      Keeping both tick marks together, pivot the strip about the second tick mark until another straight portion of that line is aligned.

e.       Continue this process until the measurement is completed, then place the paper strip on the appropriate bar scale and determine the round distance measured.

11. Contour Interval.  Contour interval appears in the center lower margin. States the vertical distance between adjacent contour lines on the map.

12. Grid Box.  Gives basic instruction on reading grids in determination of specific points on the map.

13. Declination Diagram.  It is located in the lower left margin of the large scale and map indicates the angular relationship of true north, grid north and magnetic north.  Shown in Figure 2.

14. Legend:

a.       Located in the lower left margin.

b.      Illustrates and identifies some of the symbols on the map.

c.       eVERY TIME a map is used, refer to the Legend to prevent errors in symbol identification.

15. Grid System:

a.       A system of letting us tell someone where specific locations or points are.

b.      A network of lines, in the form of squares placed on the face of the map.

c.       These squares are somewhat like the blocks formed by the street system of a city.

d.      The "streets" in a grid all have very simple names.  The names are all numbers.

e.       Every tenth line is made heavier in weight.  This will help you find the line you are looking for.

f.        Each grid line on the map has its own number.  These numbers appear within the map on the line itself.  Four digit numbers identify a 1000 square meter grid square.  Six digits identify a 100-meter grid square and eight digits identify a 10-meter grid square.

g.       To locate a point by grid reference is a simple matter.  We follow a simple rule of map reading: READ RIGHT AND UP.  Locate grid coordinate  303507 on the map in the next figure.