The methods of range estimation used during this period are--
• 100-meter unit of measure method.
• Appearance of objects method.
• Front sightpost method.
1. 100-METER UNIT OF MEASURE METHOD - To perform this method, the Soldier must be able to visualize a distance of 100 meters on the ground.
• For ranges up to 500 meters, he determines the number of 100-meter increments between the two points.
• Beyond 500 meters, the Soldier selects a point halfway to the target, determines the number of 100-meter increments to the halfway point, and then doubles it to find the range to the target.
During training exercises, the Soldier must "become familiar with the effect that sloping ground" has on the appearance of a 100-meter increment.
• Ground that slopes upward gives the illusion of greater distance, and observers tend to underestimate a 100-meter increment.
• Ground that slopes downward gives the illusion of shorter distance, and observers tend to overestimate a 100-meter increment.
Proficiency in the 100-meter unit of measure method requires constant practice. While training this technique, comparisons should be made continually between the range as determined by the Soldier and the actual range as determined by pacing or other more accurate means of measurement. NOTE: The best training technique is to require the Soldier to pace the range after he has visually determined it. In this way, he discovers the actual range for himself, which makes a much greater impression than if he is simply told the correct range. The greatest limitation of the 100-meter unit of measure method is that its accuracy is directly related to the amount of terrain visible to the observer. This is particularly true at longer ranges. If a target appears at a range of 500 meters or more and the observer can see only a portion of the ground between himself and the target, it becomes very difficult to use the 100-meter unit of measure method with any degree of accuracy.
2. APPEARANCE OF OBJECTS METHOD - The appearance of objects method is a means of determining range by the size and other details of the object observed. This is a common method of determining distances and is used by most people in their everyday living. For example, a motorist attempting to pass another car must judge the distance of oncoming vehicles based on his knowledge of how vehicles appear at various distances. Suppose the motorist knows that, at a distance of one mile, an oncoming vehicle appears to be 1 inch wide and 2 inches high. Then, any time he sees other oncoming vehicles that fit these dimensions, he knows they are about one mile away. The rifleman can use this technique to determine ranges on the battlefield. If he knows the characteristics, size, and detail of personnel and equipment at known ranges, he can compare these characteristics to similar objects at unknown ranges. When the characteristics match, so do the ranges. To use the appearance of objects method with any degree of accuracy, the Soldier must be thoroughly familiar with the details of objects as they appear at various ranges. For example, the Soldier should "study the appearance of a man standing at a range of 100 meters." He fixes the man’s appearance firmly in his mind, "carefully noting details of size and the characteristics of uniform and equipment." Next, he studies the same man in a kneeling position and in a prone position. By comparing the appearance of Soldiers in these positions at known ranges from 100 to 500 meters, the Soldier can establish a series of mental images that will help him determine range on unfamiliar terrain. NOTE: Training should also be conducted in the appearance of other familiar objects, such as weapons or vehicles. Because the successful use of this method depends upon visibility, anything that limits visibility (for example, weather, smoke, or darkness) will limit the effectiveness of this method.
3. FRONT SIGHTPOST METHOD - Using the front sightpost as a scale is another method of estimating range. This method can be used for a quick on-the-spot estimation and engagement.
• Generally, if a man-sized target is ½ of the width of the front sightpost, the target is approximately 300 meters away. • If the target is ¼ of the width of the front sightpost, the target is approximately 600 meters away.