Devil Dogs

a. Map Scale. A map is a graphic representation of a portion of the earth’s surface in a uniform and proportional relationship. This relationship is known as the map scale. The scale of the map permits the determination of ground distance from the map.

b. Representative Fraction (RE). The numerical scale of a map expresses the ratio of horizontal distance on the map to the corresponding horizontal distance on the ground. It is usually written as a fraction; for instance, a map scale of 1:25,000 or 1:50.000. to 50,000 inches on the ground)

c. Graphic Bar Scale. This scale is the quickest method of determining distance from a map or aerial photo. The graphic bar scales are located in the center of the lower margin. They are the rulers used to convert map distance to ground distance. Maps usually have three or more bar scales, each in a different unit of measure. Each bar scale has a primary scale marked in units of measure and an extension scale divided into tenths of the unit of measure.

d. Straight Line Distance. To determine a straight line, ground distance, between two points on a map, the sniper xviii:

1) Lay a straight edged piece of paper on the map so that the edge of the paper touches both points.

2) Make a tick mark on the edge of the paper at each point. The pencil point must be as sharp as possible.

3) Move the paper down to the graphic bar scale and read the distance in the desired unit of measure between the two points.

e. Curved Line Distance. To measure distance along a winding road, stream, or any curved line between two points on a map, the sniper will:

I) Lay a straight edged piece of paper on the map so that the edge of the paper touches one of the points at or near the end of the paper. All measurements are made in the middle of the road, stream, etc.

2) Make a tick mark on the map and the paper at the point.

3) Keeping the marks together, align the edge of the paper along a straight portion and make a tick mark on both the map and the paper at the end of the aligned portion.

4) Keeping the tick marks together, place the point of the pencil on the paper’s tick mark to hold it in place.

5) Pivot the paper until another straight portion is aligned and make a tick mark on both paper and map.

6) Continue this technique until the other point is reached.

7) Move the paper down to the graphic bar scale and read the distance between the two points just as with the straight line measurement.

f. Marginal Notes. Marginal notes may give the road distance from the edge of the map to a town, highway, or junction off the map. If the distance is needed from a point on the map to a point off the map, the distance is measured to the edge of the map and the distance specified in the margin is added.

a. Grid and Magnetic Azimuths.

1) Azimuths measured with a protractor are referred to as grid azimuths and cannot be used with a compass until converted to magnetic azimuths.

2) An azimuth obtained with a compass cannot be plotted on a map until it is converted to a grid azimuth.

3) To convert azimuths and orient the map properly, large scale maps have a declination diagram placed in the lower margin of the map.

b. Declination.
Declination is the angular difference between true north and either magnetic or grid north. There are two declinations: a magnetic and a grid. True north has no application in navigating with a map and compass, it is used when navigating by the stars. Declinations can be either east or west since grid and magnetic north can be to the left or right of true north.

1) The declination diagram in the lower margin of the map contains three prongs representing magnetic north, grid north, and true north. The angles shown in the declination diagram are not to scale, and if the angles are measured with the protractor, their values would not be the values shown.

2) Declination diagrams may appear in several forms, depending on the age of the map in use. Regardless of the form of the diagram. the sniper’s first concern in using it to convert an azimuth is to determine how much deviation there is between grid north and magnetic north. The diagram shows the interrelationship of magnetic north, grid north, and true north.

3) The deviation between grid north and magnetic north is known as the GM angle.

a) It is always measured from grid to magnetic.

b) Depending upon the locality and the declination, the GM angle can be either east or west depending on the location of magnetic north in relation to grid north.

c) Since the GM angle is measured from grid to magnetic, if magnetic is east or right of grid, GM angle is easterly.

4) Generally, all military maps show the GM angle in the declination diagram. Conversion notes explain the use of the GM angle when converting magnetic azimuths to grid azimuths and vice versa.

5) To convert azimuths, the sniper performs the following steps:

a) Place a finger on the symbol for the base direction converting from.

b) Move the finger to the symbol for the base direction converting to.

c) Apply the LARS (left add, right subtract) rule:

I If the finger is moved to the left, add the GM angle.

2 If the finger is moved to the right, subtract the GM angle.

d) The azimuth is now converted to the desired base direction.

C. Annual Declination Change.

1) In some areas, magnetic north changes constantly, requiring the map user to update the map.

a) An annual magnetic change note will appear under the declination diagram.

b) It will give the magnetic declination for a certain year, the amount this angle changes each year, and in what direction it changes.

c) The change in magnetic declination changes the GM angle.

2) Whenever plotting something very important (like a route to a mission area) the sniper must be sure to check this.

a) The Indian Head map drafted in 1960 has a GM angle of 5 degrees 30 minutes west with an annual declination change of 2 minutes west.

b) Using this map in 1990, a difference of thirty years, an adjustment is necessary. If the annual declination of 2 minutes west is multiplied by thirty years, the GM angle change is 60 minutes or 1 degree west.

Basic Requirements:
Male or female age 17-30.
If 17, have parental consent or be legally emancipated.
Possess a high school diploma or equivalent.
Be physically and mentally qualified by a MEPS doctor.
Pass the ASVAB with a minimum score of 33 AFQT.
Pass an Initial Strength Test (IST)
Have no felony convictions and not be on probation.
Have no outstanding warrants or parking tickets.
Have no illegal drug use other than marijuana and no drug use in the last 6 months.

I am a Staff Non-Commissioned Officer in the United States Marine Corps. As such, I am a member of the most unique group of professional military practitioners in the world. I am bound by duty to God, Country, and my fellow Marines to execute the demands of my position to and beyond what I believe to be the limits of my capabilities. I realize I am the mainstay of Marine Corps discipline, and I carry myself with military grace, unbowed by the weight of command, unflinching in the execution of lawful orders, and unswerving in my dedication to the most complete success of my assigned mission. Both my professional and personal demeanor shall be such that I may take pride if my juniors emulate me, and knowing perfection to lie beyond the grasp of any mortal hand, I shall yet strive to attain perfection that I may ever be aware of my needs and capabilities to improve myself. I shall be fair in my personal relations, just in the enforcement of discipline, true to myself and my fellow Marines and equitable in my dealings with every man.