MSL101L04 Basic Map Reading SR.pdf lesson 4.pdf

Figure 5 8 constructing a time distance scale other

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Figure 5-8. Constructing a time-distance scale OTHER METHODS 5-19. Determining distance is a common source of error encountered while moving, either mounted or dismounted. There may be circumstances when it is not possible to determine distance using a map. It is essential to learn methods to accurately pace, measure, use subtense, or estimate distances on the ground. P ACE C OUNT 5-20. A pace is equal to one natural step, about 30 inches long. To use the pace count method accurately, a Soldier knows how many paces it takes to walk 100 m. To determine this, walk an accurately-measured course and count the number of paces it takes to reach 100 m. (A pace course can be as short as 100 m or as long as 600 m.) The pace course, regardless of length, is on similar terrain as that to be walked over. It does
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15 November 2013 TC 3-25.26 6-1 Chapter 6 Directions Being in the right place at the prescribed time is necessary for successfully accomplishing military missions. Direction plays an important role in a Soldier’s everyday life. It can be expressed as right, left, straight ahead, and so forth; but then the question arises, “To the right of what?” This chapter defines the word azimuth and the three different norths. It explains in detail how to determine the grid and the magnetic azimuths with the use of the protractor and the compass. It explains the use of some field-expedient methods to find directions, the declination diagram, and the conversion of azimuths from grid to magnetic, and vice versa. It also includes some advanced aspects of map reading such as intersection, resection, modified resection, and polar plots. METHODS OF EXPRESSING DIRECTION 6-1. Military personnel need a way of expressing direction that is accurate, adaptable to any part of the world, and has a common unit of measure. Directions are expressed as units of angular measure, such as— Degree. The most common unit of measure is the degree (º) with its subdivisions of minutes (') and seconds ("). (See Chapter 4.) Mil. Another unit of measure, the mil (abbreviated m/ in graphics), is used mainly in artillery, tank, and mortar gunnery. The mil expresses the size of an angle formed when a circle is divided into 6400 angles, with the vertex of the angles at the center of the circle. A relationship can be established between degrees and mils. A circle equals 6400 mils divided by 360 degrees, or 17.78 mils per degree. To convert degrees to mils, multiply degrees by 17.78. Grad. The grad is a metric unit of measure found on some foreign maps. There are 400 grads in a circle (a 90-degree right angle equals 100 grads). The grad is divided into 100 centesimal minutes (centigrads) and the minute into 100 centesimal seconds (milligrads). BASE LINES 6-2. To express direction as a unit of angular measure, there is a starting point or zero measure, and a point of reference. These two points designate the base, or reference line. The three base lines include true north, magnetic north, and grid north. (See Figure 6-1.) The most commonly used base lines are magnetic and grid. To explain further:
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