Tactical Tools (Corporal's Course)

Most man-made interference comes from electrical sources such as:

-Power generators -Power lines -M998/1038, M1043/44/45/46 HUMVEE -Faulty electrical relay contacts The key to combating this form of interference is to isolate communications equipment from man-made interference. The interference from known sources such as generators can be greatly reduced if an antenna is positioned so that an obstacle (e.g., a hill) is between it and the source. This must be done so that the same obstacle will not block the intended radio path.

Selection and Use of Steering Marks

A steering mark is a well-defined guiding object on an azimuth. These can be natural or man-made (e.g., hill, tree, building, etc.), a celestial body (sun, stars, moon), or another person. Whether you are navigating during daylight or periods of reduced visibility, through densely wooded areas or open terrain, or over short or great distances, every step you take should be toward a selected steering mark.

Military Protractor

Although we have a 6-digit coordinate to help us pinpoint a location, military maps do not have 100-meter squares that help you to do this. To help us determine a 6-digit coordinate, we use a protractor. Identify the correct triangle on the protractor based on the map scale. The correct triangle will have a horizontal and vertical axis that matches the grid squares on your map.

Minor Terrain Features (Elevation and Relief)

6. DRAW A draw is a less developed stream course than a valley. Standing in a draw, the ground slopes upward in three directions and downward in the other direction. The contour lines depicting a draw are U-shaped or V-shaped, pointing toward high ground. In a draw, there is essentially no level ground and little or no maneuver room within its confines. 7. SPUR A spur is a short, continuous sloping line of higher ground, normally jutting out from the side of a ridge. The ground is sloped down in three directions and up in one direction. Contour lines on a map depict a spur with the U- or V-shaped lines pointing away from high ground. A spur is often formed by two rough parallel streams, which cut draws down the side of a ridge. 8. CLIFF A cliff is a vertical or near vertical feature; it is an abrupt change of the land. When a slope is so steep that the contour lines converge into one "carrying" contour of contours, this last contour line has tick marks pointing toward low ground. Cliffs are also shown by contour lines close together and, in some instances, touching each other.

Declination Diagram

Declination diagram is the angular difference between true north and either magnetic or grid north. There are two declinations: A magnetic declination A grid declination The declination diagram shows the angular relationship, represented by prongs, among these three types of north.

A ___________ is a planned magnetic deviation to the right or left of an azimuth to an objective.

Deliberate offset

A __________ is a low point in the ground or a sinkhole.

Depression

FREQUENCY BANDS AND CHARACTERISTICS

Each frequency band has certain characteristics. The ranges and power requirements are for normal operating conditions (proper siting, antenna orientation, and correct operating procedures). The ranges will change according to the condition of the propagation medium and the transmitter output power. Using the correct frequency is extremely important. Never leave your frequency unless a higher authorizes you to do so. Always ensure that you are using the correct frequency. There are three tactical single channel frequency bands: -High Frequency (HF) long-distance -Very High Frequency (VHF) short-distance -Ultrahigh Frequency (UHF) short-distance

G-M Angle

G-M angle (grid-magnetic angle) value is the angular size that exists between grid north and magnetic north and the year it was prepared. This value is expressed to the nearest 1/2 degree, with mil equivalents shown to the nearest 10 mils. The G-M angle is important to the map reader/land navigator, because it will affect the accuracy of navigation skills in the field.

G-M Conversion

G-M conversion is applying the angular difference between the grid north and the magnetic north to convert compass readings to grid version for use in navigation. Since the location of this magnetic field does not correspond exactly with the grid-north lines on the maps, a conversion from magnetic to grid or vice versa is needed. Simply refer to the conversion notes that appear in conjunction with the diagram explaining the use of the G-M angle. One note provides instructions for converting a magnetic azimuth to a grid azimuth, and the other, for converting a grid azimuth to a magnetic azimuth. The conversion (add or subtract) is governed by the direction of the magnetic-north prong relative to that of the north-grid prong.

14 Grid Reference Box (Bottom Margin)

Grid Reference Box

Four-Digit Grid

Grid lines are a series of straight lines intersected to form a series of squares. Two digits are printed in large type at each end of the grid lines. These numbers will be the main reference for finding your grid or location. Vertical grid lines run from top to bottom of the map sheet: grid north/south. Horizontal grid lines run left to right of the map sheet: grid west/east.

Very High Frequency (VHF) short-distance numbers:

Ground Wave Range = 0-30 miles Sky Wave Range = 50-150 miles Power Required = .5 or less kW

High Frequency (HF) long-distance numbers:

Ground Wave Range = 0-50 miles Sky Wave Range = 100-8000 miles Power Required = .5-5 kW

Ultrahigh Frequency (UHF) short-distance numbers:

Ground Wave Range = 0-50 miles Sky Wave Range = N/A Power Required = .5 or less kW

Which of the following are limitations that can impair the performance of a lensatic compass? Select all that apply.

High-tension power lines. YES Field gun, truck, or tank. YES Telegraph or telephone wires and barbed wire. YES Machinegun. YES

Blue (Colors on a Map)

Identifies hydrography or water features such as lakes, swamps, rivers, and drainage.

Advantages the center-hold technique:

It is fast and easy to use. It can be used under all conditions of visibility. It can be used when navigating over any type of terrain. It can be used without putting down the rifle; however, the rifle must be slung back over either shoulder.

Setting a Course

It is impractical for you to keep your compass out at all times when following a desired course. These steps will allow you to preset your compass to your course. 1. Set the azimuth directly under the black line index. 2. Rotate the bezel to north arrow.

Which of the following are advantages of the center-hold technique? Select all that apply.

It is the most accurate to use. NO It is faster and easier to use. YES It can be used under all conditions of visibility. YES It can be used when navigating over any type of terrain. YES

EFFECTS OF METAL AND ELECTRICITY

Metal objects and electrical sources can affect the performance of a compass. However, nonmagnetic metals and alloys do not affect compass readings. The separation distances are: High-tension power lines 55 meters Field gun, truck, or tank 18 meters Telegraph or telephone wires and barbed wire 10 meters Machine gun 2 meters Rifle 1/2 meters

Advantages of the compass-to-cheek technique:

More accurate when getting an azimuth or steering marker Ideal when employing intersection and resection techniques

Radio frequency interference is

always present in a military environment. It may come from a single source or a combination of many sources including natural or man-made interference. Frequency interference can derive from: -Poor equipment condition -Improper equipment usage -The use of unauthorized frequencies -Frequency reuse

Elevation and Relief

Terrain features do not normally stand alone.

STRAIGHTEDGE METHOD

The straightedge method is used when a compass is not available, use the straightedge method of intersection. With the position in view, use the following steps: 1. Orient the map 2. Locate your position 3. Rotate using a straightedge 4. Draw a line 5. Repeat to next position 6. Determine Coordinates

5 Series Number (Top Margin)

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).

1 Sheet Name (Top Margin)

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.

2 Sheet Number (Top Margin)

The sheet number is bolded in 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.

Sighting Wire

The sighting wire provides an exact azimuth for objects. It can be used for compass calibration. It is also used with steering marks.

Green (Colors on a Map)

This color identifies vegetation with military significance, such as woods, orchards, and vineyards.

Black (Colors on a Map)

This color indicates cultural (man-made) features such as buildings and roads, surveyed spot elevations, and all labels.

10 Declination Diagram (Bottom Margin)

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 new maps, there is a note indicating the conversion of azimuths from grid to magnetic and from magnetic to grid next to the declination diagram.

9 Elevation Guide (Bottom Margin)

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.

12 Contour Interval Note (Bottom Margin)

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 new maps, the contour interval is given in meters instead of feet.

Marginal Information (Bottom Margin 7-14)

This portion of the map includes information that helps to interpret the map. It provides correlation between actual terrain and man-made features and the map's topographic symbols. Some information found in the bottom margin is repeated from the top margin.

UHF radios are used for

forward air control (FAC) ground-to-air communication. Line of sight between radios is critical for reliable communications. Significant range differences are encountered between UHF radios employed for ground-to-air and ground-to-ground communications. Greater range is achieved when employed from ground-to-air communications because of the increased line of sight. When UHF radios are employed in the frequency hopping mode, the following operating factors must be understood for proper operation: -Hopset -Time of day -Antenna placement -Power setting

A line checkpoint is a

natural or manmade linear feature that crosses your line of march. The advantages of line checkpoints are: -They are usually easy to identify upon arrival. -Because they stretch across your route, you are certain to hit it, even if you stray. The disadvantages of line checkpoints are: -You may not know your exact location on that feature unless you perform a resection or inspection. -They can be confused with features that are similar to them.

The center-hold technique is effective because

it is quick and adaptable.

The primary advantage of using HF radio is

its capability to provide long-range, over the horizon (OTH) communication. Successful data communications over the HF range depends on several factors: -Equipment siting -Proper equipment grounding -Types of antennas used -Tactical employment of radio equipment -Path assessment and analysis -Frequency planning and assignment

Resection is the method of

locating one's position on a map by determining the grid azimuth to a well-defined location that can be pinpointed on the map. The two methods are: 1. ONE POINT RESECTION A one-point resection is the method of locating one's position on a map when a person is located on a linear feature on the ground such as a road, canal, or stream. The steps to conduct a one-point resection are: Step 1: Orient the map. Step 2: Find a distant point. Step 3: Determine the magnetic azimuth. Step 4: Convert the magnetic azimuth to a grid azimuth. Step 5: Convert the grid azimuth to a back azimuth. Step 6: Your location is where the line crosses the linear feature. 2. TWO-POINT RESECTION A two-point resection is the method of locating one's position on the map when the person is not located around a linear feature on the ground. The steps to conduct a two-point resection are: Step 1: Orient the map. Step 2: Identify two or three known distant locations. Step 3: Measure the magnetic azimuth. Step 4: Convert the magnetic azimuth to a grid azimuth. Step 5: Convert the grid azimuth to a back azimuth. Step 6: Repeat the steps for a second position and a third position, if desired. Step 7: The intersection of the lines is your location.

Determine an Azimuth

Use your compass to determine or follow an azimuth. The arrow on the compass points toward magnetic north. 1. Raise the compass to eye level. 2. Align the center of the sighting slot. 3. Align the front hairline. The azimuth, in degrees, is the red number on the dial lying directly under the black index line of the compass crystal. The azimuth, in mils, is the black number on the outer perimeter of the dial.

A checkpoint is a

predetermined point on the ground used as a means of controlling movement or reference for location. The types of checkpoints selected should assist the leader's navigation.

The compass-to-cheek technique is more accurtae than

the center-hold technique, and it is ideal when employing intersection and resection, or when an accurate azimuth is required.

A back azimuth is

the opposite direction of an azimuth. It is comparable to doing an "about face." To obtain a back azimuth from an azimuth, add 180 degrees if the azimuth is 180 degrees or less; subtract 180 degrees if the azimuth is more than 180 degrees. The back azimuth of 180 degrees may be stated as 0 degrees or 360 degrees. When an azimuth is plotted on a map between point A (starting point) and point B (ending point), the points are joined together by a straight line. A protractor is used to measure the angle between grid north and the drawn line, and this measured azimuth is the grid azimuth. Be careful when converting azimuths into back azimuths, as a mistake could be disastrous.

Compasses are

the primary navigation tools to use when moving in an outdoor world where there is no other way to find directions. The lensatic compass is the most common and simple instrument for measuring direction. A reliable tool that will never lose signal or run out of batteries.

Tactical radio is

the principal means of communications support for MAGTF maneuver units. Principle characteristics of tactical radios: -Easy to operate -Networks are easily established -Rapidly reconfigured -Easily maintained on the move -Secure voice communications -Limited data information exchange

Major Terrain Features (Elevation and Relief)

1. Hill A hill is an area of high ground. From a hilltop, the ground slopes down in all directions. A hill is shown on a map by contour lines forming concentric circles. The inside of the smallest closed circle is the hilltop. 2. VALLEY A valley is reasonably level ground bordered on the sides by higher ground. A valley may or may not contain a stream course. Contour lines indicating a valley are U- or V-shaped and tend to parallel a stream before crossing it. The closed end of the contour line (U or V) always points upstream or toward high ground. A valley generally has maneuver room within its confines. 3. RIDGE A ridge is a sloping line of high ground. Standing on the centerline of a ridge, you will normally have low ground in three directions and high ground in one direction with varying degrees of slope. Contour lines forming a ridge tend to be U-shaped or V-shaped. The closed end of the contour lines points away from high ground. Crossing a ridge at right angles, you will climb steeply to the crest and then descend steeply to the base. When moving along the path of the ridge, depending on the geographic location, there may be an almost unnoticeable slope or a very obvious incline. 4. SADDLE A saddle is a dip or low point between two areas of higher ground. If you are in a saddle, there is high ground in two opposite directions and lower ground in the other two directions. Contour lines for a saddle typically resemble an hourglass. A saddle is not necessarily the lower ground between two hilltops; it may be simply a dip or break along a level ridge crest. 5. DEPRESSION A depression is a low point in the ground or a sinkhole. It could be described as an area of low ground surrounded by higher ground in all directions, or simply a hole in the ground. Depressions are represented by closed contour lines that have tick marks pointing toward low ground. Usually, only depressions that are equal to or greater than the contour interval will be shown.

Three types of contour lines used on a standard topographic map:

1. Index Starting at zero elevation or mean sea level, every fifth contour line is a heavier line. These are known as index contour lines. Each index contour line is typically numbered at some point. This number is the elevation of that line. 2. Intermediate The contour lines falling between the index contour lines are called intermediate contour lines. These lines are finer and do not have their elevations given. There are normally four intermediate contour lines between index contour lines. 3. Supplementary These contour lines resemble dashes. They show changes in elevation of at least one-half the contour interval. These lines are normally found where there is little change in elevation, such as on fairly level terrain.

There are two methods of using intersections:

1. Map and Compass Method 2. Straightedge Method

How to do the center-hold technique:

1. Open the compass. 2. Set the lense (rear site). 3. Position your thumb. 4. Position your finger. 5. Position your elbow.

How to do the compass-to-cheek technique:

1. Position the cover. 2. Fold the rear site. 3. Align the front site hairline. 4.. Read the azimuth.

Man-made Terrain Features (Elevation and Relief)

9. CUT A cut is a man-made feature resulting from cutting through raised ground, usually to form a level bed for a road or railroad track. Cuts are shown on a map when they are at least 10 feet high, and they are drawn with a contour line along the cut line. This contour line extends the length of the cut and has tick marks that extend from the cut line to the roadbed, if the map scale permits this level of detail. 10. FILL A fill is a man-made feature resulting from filling a low area, usually to form a level bed for a road or railroad track. Fills are shown on a map when they are at least 10 feet high, and they are drawn with a contour line along the fill line. This contour line extends the length of the filled area and has tick marks that point toward lower ground.

A map is defined as __________.

A graphic representation of a portion of the Earth's surface drawn to scale, as seen from above.

TERRAIN ASSOCIATION

A map can be oriented by terrain association when a compass is not available or when the user has to make many quick references as he moves across country. Using this method requires careful examination of the map and the ground, and the user must know his approximate location. The technique of moving by terrain association is more forgiving of mistakes and far less time-consuming than dead reckoning. Here are some features of terrain association: -It best suits those situations that call for movement from one area to another. Errors made using terrain association are easily corrected because you are comparing what you expected to see from the map to what you do see on the ground. -Errors are anticipated and will not go unchecked. -Periodic position-fixing through either plotted or estimated resection will also make it possible to correct your movements, call for fire, or call in the locations of enemy targets or any other information of tactical or logistical importance.

Marginal Information

A map is considered equipment. To use it properly, you should read the instructions. These instructions on the outer edges of the map are called marginal information. All maps are different so examine the marginal information on each map carefully.

Contour Interval

Before the elevation of any point on the map can be determined, you must know the contour interval for the map you are using. The contour interval measurement given in the marginal information is the vertical distance between adjacent contour lines. To determine the elevation of a point on the map, find the numbered index contour line closest to the point you are trying to determine. Determine if the point is a higher or lower elevation than the index contour line. Once that is established, you can count the number of contours higher or lower and, by referencing the marginal data, determine your actual elevation.

Orienting the Map

Before you can use a map, you must ensure that the map is oriented. When you orient a map, you are adjusting it so that north on the map points to north on the ground. When done correctly, the information on the map will match the features on the ground. To ensure that your map and compass are oriented, perform the following steps: 1. Determine the direction of the madnetic north and the G-M angle on the declination diagram. 2. Align the straightedge on the compass with a north-south grid line. 3. rotate the map and compass together, aligning the magnetic arrow and the fixed black index line. 4. rotate the map and compass together until the compass arrow is aligned with the magnetic north. 5. check the compass reading.

Colors on a Map

By the fifteenth century, most European maps were carefully colored. Profile drawings of mountains and hills were shown in brown. Rivers and lakes were shown in blue. Vegetation was shown in green. Roads were shown in yellow. Special information was shown in red. A look at the legend of a modern map confirms that the use of colors has not changed much over the past several hundred years. To facilitate the identification of features on a map, the topographical and cultural information is usually printed in different colors.

Which of the following are the proper techniques for holding a compass and getting an azimuth? Select all that apply.

Center-hold technique,Compass-to-cheek technique.

INSPECTIONS

Compasses are delicate instruments and should be cared for accordingly. A detailed inspection is required when first obtaining and using a compass. Your inspection should ensure: -The floating dial's glass and crystal parts are not broken. -The numbers on the dial are legible. -The floating dial does not stick. -The sighting wire is straight. -The bezel ring produces distinct clicks when turned. You should also periodically check the compass's accuracy at a declination station. If your compass varies more than three degrees, you should not use it.

Contour Lines

Contour lines are the most common method of showing relief and elevation on a standard topographic map. A contour line represents an imaginary line on the ground, above or below sea level. All points on the contour line are at the same elevation. The elevation represented by contour lines is the vertical distance above or below sea level. The three types of contour lines used on a standard topographic map are: Index lines Intermediate lines Supplementary lines

__________ are used to find the location of an unknown point by simultaneously occupying at least two known positions on the ground and then map sighting on the unknown location.

Intersections

Six-Digit Grid

Like the 4-digit grid, the 6-digit grid uses the right-and-up rule. Break the grid square down into 10 sections. The 3rd digit, the number three, will be read right and the 6th digit, the number seven, will be read up. Navigating within 1,000 meters using a grid coordinate is generally too broad an area to find a location. To improve navigation, we break down the 1,000-meter square into 100 smaller squares that are 100-meters by 100-meters on the ground. This will allow you to get 10 times closer to the objective. -To navigate within a range of 100 meters, we add numbers to our 4-digit coordinate 3050. -The additional numbers are added to both the horizontal and vertical measurements, creating the 6-digit coordinate 303507.

MAP AND COMPASS METHOD

Map and compass method is used to locate distant or inaccessible points or objects, such as enemy targets and danger areas. You can locate positions by intersecting azimuths using your map and compass. With the position in view, use the following steps: 1. Orient the Map 2.Mark your Position of the Map 3. Determine the Magnetic Azimuth 4. Convert the Magnetic Azimuth 5. Draw a Line on the Map 6. Move to a second known Point 7. Determine the Grid Coordinates

8 Adjoining Sheets (Bottom Margin)

Maps at all standard scales contain a diagram that illustrates the adjoining sheets. 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 of the same scale, whether published or planned, 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.

Natural Interference

Natural radio noise has two principal sources, thunderstorms (atmospheric noise) and stars (galactic noise). It is especially noticeable at night when the lower frequencies propagate farther than in the daytime. The only way to reduce this type of interference is to use a directional antenna to prevent receiving the interference from all directions. However, this will not eliminate the noise coming from the direction of the received signal. Use of a higher frequency will also help, although if a sky wave circuit is used, care must be exercised not to pick the highest frequency at which the signal will be refracted to Earth by the ionosphere (i.e., the critical frequency).

RADIO OPERATIONS UNDER UNUSUAL CONDITIONS

Tactical radio equipment has certain capabilities and limitations that must be carefully considered when operating in extreme areas. However, in spite of significant limitations, radio is the normal means of communications in such areas. One of the most important capabilities of radio in these areas is its versatility. -Vehicular-mounted radios can be moved relatively easily to almost any point where it is possible to install a command headquarters. -Smaller, man-packed radios can be carried to any point accessible by foot or aircraft.

Desert Areas

Tactical radio is usually the primary means of communications in the desert. It can be employed effectively in desert climate and terrain to provide the highly mobile means of communications demanded by widely dispersed forces. However, desert terrain provides poor electrical ground, and counterpoises are needed to improve operation. For the best operation in the desert, radio antennas should be located on the highest terrain available. Transmitters using whip antennas in the desert will lose one-fifth to one-third of their normal range because of the poor electrical grounding characteristics of desert terrain. For this reason, it is important to use complete antenna systems such as horizontal dipoles and vertical antennas with adequate counterpoises.

EIGHT-DIGIT GRID

The 8-digit grid begins the same as both 4- and 6-digit grids. Using the grid square divided in ten parts, you then divide it even further. The fourth digit will be read right and estimated. The eighth digit will be read up and estimated. To navigate within a range of 10 meters, we add numbers to our 6-digit coordinate 303507. The additional numbers are added to both the horizontal and vertical measurements creating an 8-digit coordinate 3034 5074. -Remember, slide the protractor to the right until vertical grid line 30 intersects the horizontal scale at the 100-meter reading "3" and the 10-meter reading "4." -This point, 3034, is your "right" reading. -Next, slide the protractor up, stopping at the horizontal grid line 50. -Use the vertical scale to measure to the 100-meter reading "7," and then the 10-meter reading "4." -This point is not only your "up" reading, 5074, but also the location of your 8-digit coordinate 30345074.

Military Grid Reference System

The Military Grid Reference System (MGRS) is the geographic standard used by the United States armed forces and NATO for locating any point on the Earth. The number of digits represents the degree of precision to which a point has been located and measured on a map—the more digits the more precise the measurement. A 4-digit grid is accurate to within 1000-meters. A 6-digit grid is accurate to within 100-meters. An 8-digit grid is accurate to within 10-meters.

Bezel Ring

The bezel ring holds the upper glass crystal in place. It helps preset a direction for night compass navigation. It contains 120 clicks when rotated fully. Each click equals 3 degrees.

Black Index Line

The black index line is a stationary line used as a reference line for determining direction. It identifies the direction the compass is pointing when held properly.

Base

The body of the compass contains the following movable parts: The floating dial The fixed black index line The bezel ring The thumb loop

Reddish-Brown (Colors on a Map)

The colors red and brown are combined to identify cultural features such as boundaries and major roads, all relief features, non-surveyed spot elevations, and elevations or contour lines.

Compass Dial

The compass dial floats free when in use. It is locked in place by closing the eyepiece. It contains two complete circular scales, one in degrees (red scale) and one in mils (black scale). The magnetic arrow is found on the compass dial.

Cover

The cover contains a sighting wire. When closed, it protects the face of the crystal. When at a 90 degree angle to the other half of the compass, it can be used to sight on objects. The cover includes a graduated straightedge that is referenced when orienting the map.

6 Edition Number (Top Margin)

The edition number is found bolded 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. This date is important when determining how accurately the map data might be expected to match what you will encounter on the ground.

Combination Checkpoints

The ideal type of checkpoint is one that is either a combination of two line checkpoints or a line checkpoint and a point checkpoint. The advantages of combination checkpoints are: -Since the linear feature stretches across your route, you cannot miss it. Once at the linear feature, you need only follow it until you come to the point feature. You are then at your checkpoint. -Since you can accurately determine an exact point on the ground from this type of checkpoint, it offers you information about distance and direction.

7 Boundaries (Bottom Margin)

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.

13 Legend (Bottom Margin)

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 the same on every map. Always refer to the legend to avoid errors when reading a map.

Lens

The lens is used to read the dial. It is housed in the rear-sight. The rear-sight slot is used in conjunction with the sighting wire to sight objects. The rear-sight serves as a lock. It clamps the dial when it is closed for its protection. The rear-sight must be opened more than 45° to allow the dial to float freely.

Compass Nomenclature

The lensatic compass consists of three major parts: Cover Base Lens

CARE AND MAINTENANCE

The lensatic compass was built to increase its serviceable life. Adherence to a very simple maintenance regimen will significantly increase the life of the lensatic compass. Maintenance requirements are as follows: -Rinse in fresh water, especially after exposure to salt water. -Brush off dirt and grime. -Ensure the ridges on the bezel ring are free of dirt. -Check movement of the rear sight to ensure it is free moving.

3 Series Name (Top Margin)

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.

Very High Frequency (VHF)

The primary MAGTF VHF radio is the single-channel ground and airborne radio system (SINCGARS). SINCGARS is a family of lightweight combat radios that serves as the primary means of communications for command and control and fire support on the battlefield. SINCGARS is the standard VHF-FM tactical radio for the Marine Corps. It replaced the AN/PRC-77 and the AN/VRC-12 family. -The system provides high security against the threat of electronic warfare (EW) by using frequency hopping with integrated COMSEC. -It is capable of voice and data transmission (up to 16 kbps under optimum conditions and over limited distances) over the VHF-FM frequency.

BASIC COMPONENTS OF RADIO EQUIPMENT

The radio equipment for communication between two stations and the path the signal follows through the air is called a radio link. A radio link consists of seven components: the transmitter, power supply, transmission lines, transmitting antenna, propagation path, receiving antenna, and receiver. The transmitter generates a radio signal. The power supply (i.e., battery or generator) supplies power for the operating voltage of the radio. When transmitting, the radio operator aims to provide the strongest possible signal at the site of the receiving station. The best possible signal is the signal that provides the greatest signal-to-noise ratio at the receiving antenna. To transmit the best possible signal, select or determine the: -Optimum frequency -Best antenna for that frequency based on the available space of the transmitting site -Proper propagation path

4 Scale (Top Margin)

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.

Thumb Loop

The thumb loop serves as a retaining device to secure the compass in a closed position. It is used when holding the compass in position for sighting on objects.

Marginal Information (Top Margin 1-6)

The top margin of the map helps you to identify the specific area covered as well as the age and scale of the map.

11 Bar Scale (Bottom Margin)

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.

BYPASSING OBSTACLES

To bypass enemy positions or obstacles and still stay oriented, detour around the obstacle by moving at right angles for a specified distance. Here is an example of the steps involved in bypassing an obstacle: -While moving on an azimuth of 0 degrees, change the azimuth to 90 degrees and travel for 100 meters (add 90 degrees to your original azimuth). -Change the azimuth to 0 degrees and travel for 200 meters (move along your original azimuth). -Change the azimuth to 270 degrees and travel for 100 meters (subtract 90 degrees from your original azimuth). -Finally, change the azimuth to 0 degrees and the azimuth is back on your original azimuth line.

Types of North

True North is a line from any point on the Earth's surface to the North Pole. All lines of longitude converge at the North Pole and are true north lines. A star is used to depict true north. Magnetic North is the direction to the north magnetic pole, as indicated by the north-seeking needle of a magnetic compass. Magnetic readings are used to navigate in the field. A half arrowhead is used to depict magnetic north. Grid North is the north that is established by using the vertical grid lines on the map. Grid north lines are parallel lines on the map; they do not converge at the North Pole. The letters GN are used to depict grid north.

What are the three types of north shown in the declination diagram? Select all that apply.

True north,Magnetic north,Grid north

Nomenclature and Functions

When the compass is opened, the left side is a graduated coordinate scale. In new compasses, this scale is 1:50,000 and in old compasses it is 1:25,000. Be sure to check the scale before using it. Compasses are delicate instruments and should be cared for accordingly. A detailed inspection is required when first obtaining and using a compass.

A map is defined as

a graphic representation of a portion of the Earth's surface drawn to scale, as seen from above. It uses colors, symbols, and labels to represent features found on the ground. -The ideal representation would be realized if every feature of the area being mapped could be shown in true shape. -The purpose of a map is to provide information on the existence, location, and distance between ground features, such as populated places and routes of travel and communication. It also indicates variations in terrain, heights of natural features, and the extent of vegetation cover. -All operations conducted require maps; however, the finest maps available are worthless unless the map user knows how to read them.

A deliberate offset is

a planned magnetic deviation to the right or left of an azimuth to an objective. Use it when the objective is located along or in the vicinity of a linear feature such as a road, or a stream. -Because of errors in the compass or in map reading, the linear feature may be reached without knowing whether the objective lies to the right or left. -A deliberate offset informs the navigator of the direction to travel upon reaching the linear feature.

The three types of radio modes are

simplex, half duplex, and full duplex. -Simplex mode has one station that may send information over a single frequency. An example of simplex mode would be AM/FM radio stations. -Half duplex mode has information that can be transmitted and received in either direction, but not in both directions simultaneously. An example of this is a single-channel two-way radio such as a Motorola. -Full duplex mode allows for an uninterrupted exchange of information between two stations. A telephone would be an example of full duplex mode.

Point checkpoints are

specific objects or terrain features that, if located and properly identified, positively indicate your exact location. The advantage of a point checkpoint is that it indicates precisely where you are, allowing you to correct any mistakes in both distance and direction. The disadvantages of point checkpoints are: -Because point checkpoints cover just a small area on the ground, you may miss them. -There may be many terrain features in the area that look like the feature you select as a checkpoint.

Dead reckoning means following

the desired azimuth on the compass while keeping a pace count until the unit has traveled the distance to the destination. During times of reduced visibility, terrain association can be difficult. During these times it is necessary to rely on your compass and pace count. Dead reckoning consists of two fundamental steps. -The first is the use of a protractor and graphic scales to determine the direction and distance from one point to another on a map. -The second step is the use of a compass and some means of measuring distance to apply this information on the ground. In other words, dead reckoning begins with the determination of a polar coordinate on a map and ends with the act of finding it on the ground.

Intersections are used to find

the location of an unknown point by simultaneously occupying at least two known positions on the ground and then map sighting on the unknown location.