Uses for Plotting Board M17

two plotted points, the operator must remember

that all parallel lines have the same azimuth.

Therefore, when a particular azimuth is rotated

over the index mark, every vertical line on the

grid pattern (fig. 13) is pointing along that same

azimuth. This means also that the azimuth of

any of the vertical lines of the grid pattern is

read at the index mark. To find the azimuth of

the target with respect to the firing position, ro-

tate the azimuth disk (fig. 12) until the two

pencil dots lie along one of the vertical lines on

the base grid, or, until they are the same distance

from the same vertical line with the target dot

toward the top of the plotting board. The WT

azimuth in this example may be read on the

azimuth scale at the index mark on the base.

(4) Determine the range between the firing

position and the target in meters by counting

the number of small grid pattern graduations

separating them when in the above position and

multiplying this number by 50 or 100, depending

on which scale on the grid pattern is used. The

WT range can also be determined by measuring

the distance, using one of the range scales on the

base.

e. In many cases, the index mark does not

fall exactly on one of the 10-mil graduation lines

of the azimuth scale. When this occurs, the opera-

tor computing the range must use the vernier

scale to read the azimuth to an accuracy of one

mil (fig. 21). As an example, the use of the

vernier scale for setting azimuth 5454 is shown in

the figure 21.

Note. Figure 2-1 shows vernier setting method and does

not reflect the appearance of the vernier on plotting board

M17.

Figure 21. Use of vernier scale.

2-8. Uses for Plotting Board M17

Azimuth 5454 mils

OP to target:

a. To determine initial direction and range

Distance 1500 meters

(para 2-9a).

(2) Procedure. To determine the azimuth

b. To determine WT mil values from the azi-

and range from the weapon to the target using

muth scale on the azimuth disk (para 2-9b).

the range scale along the index line (fig. 13),

where the smallest grid graduation represents

c. To solve problems involving mil relations

50 meters, proceed as indicated in (a) through

(para 2-9c).

(d) below.

d. To solve survey notes (para 2-9d).

(a) Rotate the disk until 4150 mils is read

over the index mark on the base. Mark the disk

2-9. Sample Problems

with a pencil dot over the index line at the 550-

a. Determination of the Initial Azimuth and

meter graduation. This dot represents the loca-

R a n g e From the Weapon Firing Position to the

tion of the weapon (W).

Target.

(b) Rotate the disk until 5454 mils is

(1) Given. Observation post at the center

read over the index mark on the base. Mark the

(pivot point) of the disk.

disk with a pencil dot over the index line at the

Azimuth 4150 mils

1500-meter graduation. This dot represents the

OP to weapon:

location of the target (T).

Distance 550 meters

2-4