ATP-3-09-30 Observed Fires Download
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Chapter 3 3-8 ATP 3-09.30 28 September 2017 Estimating 3-39. With a thorough terrain map analysis of the observers’ area of operations, the observer can estimate direction on the ground. As a minimum, the observer should be able to visualize the eight cardinal directions (N, NE, E, SE, S, SW, W, and NW). Because of the inaccuracy of this method, it is the least preferred method of determining direction. DISTANCE 3-40. Once a direction to the target is determined, the observer must determine a distance to the target. Distance is the horizontal space between a reference point or an observer and a target (observer-target distance). The meter is the standard unit of measurement for distance. There are several methods to determine distance. LASER 3-41. Laser range finders are the preferred means of determining the observer-target distance. When a laser range finder is used, distance may be determined to the nearest 10 meters. FLASH TO BANG 3-42. When it is necessary to verify observer-target distance, the flash to bang technique is helpful. Sound travels at a speed of approximately 350 meters per second. Use the following equation: Elapsed time (seconds) between visible impact and sound arrival x 350 meters per second = distance (meters). Count the number of seconds between the time the round impacts (flash) and the time the sound reaches the observer (bang) and multiply by 350 meters per second. The answer is the approximate number of meters between the observer and the round. (The observer can also use this procedure to determine the distance to muzzle flashes from threat weapons.) Example The observer wants to determine the approximate distance from own position to a burst. The observer begins counting when the burst appears and stops when the sound is heard. The observer counts 4 seconds. Therefore, the distance from the burst to the observers’ position is approximately 1,400 meters (350 x 4). ESTIMATION 3-43. In the absence of a more accurate method of determining distance to a target, the observer must estimate distance. The degree of accuracy in this method depends on several factors, such as terrain relief, time available, and the experience of the observer. Generally, the longer the observer remains stationary, the better this technique can be used. Mental Estimation 3-44. Use of a known unit of measurement to make a mental estimate of distance. Estimate distance to the nearest 100 meters by determining the number of known units of measure, such as a football field (100 yards), between the observer's position and a target. For longer distances, the observer may have to estimate distance progressively. To do this, the observer determines the number of units of measure (100 yards) to an intermediate point and doubles the value. The observer should consider the effects in table 3-1 when estimating distance.