1. Locate a target by polar plot given a terrain sketch and a reference point.
2. Locate a target within 100 meters expressed as a six-digit grid, given a map and a coordinate scale.
3. Determine the range and lateral shift to a target given a known point and orienting data.
2401. Polar Plot
The polar plot method of target location consists of three elements: direction, distance, and vertical shift. You determine these elements and report them to the FDC. The primary advantage of the polar plot method is that it is fast and can be done without a map. If a laser rangefinder is used, the polar plot method is very accurate. A disadvantage is that your position must be known to the firing unit. This may require you to send a coded message to your location (including altitude) before sending the call-for-fire. To perform a polar plot, follow these steps:
Step 1: Determine direction to the target to the nearest 10 mils.
Step 2: Determine/estimate the distance to the target to the nearest 100 meters.
Step 3: Determine the difference in altitude between your position and the target to the nearest 5 meters. You need not report a vertical shift of less than 30 meters.
2402. Grid Coordinate
Target location by grid coordinate is a natural extension of the polar plot method. The FDC doesn't need to know the observer's location to use the grid method. Normally you locate targets to the nearest 100 meters (six-digit grid). You do the plot on your map and refine with terrain association, then read the grid where the target plots on your map. When additional accuracy is required (for registrations or locating known points) you should locate targets to the nearest 10 meters (eight-digit grid).
b. Supplementary data. With the use of your OF fan, you can determine six-digit grids easily and, with good observations, you can determine eight-digit grids accurately. Follow these steps to determine a grid using your OF fan.
(1) Determine the direction to the target using one of the methods covered in Lesson 2.
(2) Determine distance to it with one of the methods taught in Lesson 3.
(3) Find the direction on or between the rays of the fan.
(4) Follow along the direction until you are at the determined distance by using the tick marks on the rays.
(5) Plot the point and then scale the grid from the map.
2403. Shift from a Known Point
The shift from a known point method of target location is when you locate a target in relation to a known point (fig 2-10). This method offers several advantages. It is accurate, you don't have to use a map, and your location need not be known to the FDC. However the FDC must know the location of the known point. The known point may be a terrain reference point previously recorded or a target that was previously fired and recorded. To perform a shift from a known point, follow these steps:
a. Identify the known point to be used to the FDC by target or known point number.
b. Determine the OT direction to the nearest 10 mils and report as "direction _______."
c. Determine the lateral distance between the known point and the target to the nearest 10 meters, using the mil relation formula you learned in Lesson 3, report this to the FDC as "right ____(or left ____)." If the deviation is greater than 600 mils, the mil relation formula becomes inaccurate, you should use the grid method of target location.
d. Determine the range shift from the known point to the target to the nearest 100 meters. If the target is further from you than the known point, you report "add ____." If the target is closer to you than the known point, you report "drop ____."
e. Determine the vertical difference between the known point and the target to the nearest 5 meters, if the difference is greater than 30 meters, you report this as "up ____ " (or "down____").
Figure 2-10. Shift from a known point.
Figure 2-10 gives an example of a shift from a known point method of target location. The following computations are for figure 2-10.
Mil relation formula: W = R x m R = (known distance/1000) m = (angular deviation 80m) W = 2.1 x 80 = 168.0
168.0 rounded to nearest 10 M = 170 M W = Right 170
Distance = Estimated distance - Known distance 2900 - 2100 = Add 800
Altitude = 450 - 400
Exercise: Complete items 1 through 3 by performing the action required. Check your responses against those listed at the end of this study unit.
Situation: Select the correct answers using the information given and illustrations 1 and 2.
The first illustration is your observation of your target and a stalled tank. The peak on which your reticle pattern is centered is known point 1. The distance from you to the tank is 3800 meters.
The second illustration is your oriented map and OF fan with known point 1 (KP0001) plotted at grid 714461. You have the following data for known point 1:
direction 4790, distance 5900, altitude 2450. The contour interval of the map is 20 meters.
Illustration 1.
Illustration 2.
1. What is the grid to the target?
a. 736473 c. 739467
b. 736464 d. 740471
2. What is the correct polar plot of the target?
a. DIRECTION 4745, DISTANCE 3550, DOWN 80 b. DIRECTION 4835, DISTANCE 3850, UP 80 c. DIRECTION 4840, DISTANCE 3800, DOWN 60 d. DIRECTION 5090, DISTANCE 3000, UP 60
UNIT SUMMARY
In this study unit, you learned the methods and techniques for locating targets within the target area. You learned the basics of map/terrain association and the determination of direction and distance from yourself to objects or from objects to objects. As an observer, you will be required to perform these actions repeatedly. In Study Unit 3, you will learn to call for, adjust rounds onto, and engage targets in fire for effect. In adjusting rounds and reporting their effects, you will again be required to associate your observations to the map and to determine direction and
distances.
Lesson 1 Exercise Solutions Reference
1. d. 2101
2. c. 2102
3. d. 2101c
Lesson 2 Exercise Solutions Reference
1. c. 2202
2. b. 2202b
3. b. 2203
4. c. 2204a
5. d. 2205
Lesson 3 Exercise Solutions Reference
1. b. 2301a
2. c. 2301b
3. d. 2302
4. b. 2303
Lesson 4 Exercise Solutions Reference
1. b. 2402
2. c. 2401
3. c. 2403