2. Select a point which you think is the middle point of the distance, estimate the distance to this middle point, and double your estimate to get your range. Do the same thing with half the distance, if the object is very far away.
3. Estimate the distance along a parallel line, such as a telephone line or a railroad having on it a well-defined length with which you are familiar.
4. Take the mean of several estimates made by several well-instructed men. This method is used in battle, but is not applicable to instruction or during tests.
1. Preliminary Instruction
To estimate distances by the eye with accuracy, it is first necessary that you become familiar with the appearance of the most convenient unit of length, namely 100 yards. Stake off a distance of 100 yards. Subdivide this 100 yards into four 25-yard divisions. Pace off the entire distance several times, and you will soon become familiar with the appearance of 100 yards. Next, take a distance more than 100 yards and compare it mentally with your unit of measure (100 yards) and make your estimate. Verify this estimate by pacing the distance. Do this once a day for several months, and you may become highly skilled in the art of estimating distances.
2. Preliminary Instruction
If you know how a soldier, or group of soldiers, looks at the different ranges, it will often assist you in quickly making an accurate estimate of the distance. In order to acquire skill in estimating distances by this method one must have special exercises designated to demonstrate the clearness with which details of clothing, movement of the limbs, etc., can be observed at the different ranges. Have a squad march away from you to a distance of 1,200 yards. Then have it approach you and halt every 100 yards. Each time the squad halts make a mental note of the distance, and then observe carefully its appearance, the clearness with which you can see the clothing, movements of the limbs, etc.
APPEARANCE OF OBJECTS
Become familiar with the effect which the varying conditions of light, background, etc., have upon the apparent distance of the object. Don't be content to memorize the following data, but go after the underlying reason in each case.
Objects seem nearer than they actually are: