For approximate determination and measurement of distances on the ground, the following simple methods are used: eye, according to the measured angular values of local objects, measured in steps, by time of movement, by sound and flash from a shot, by ear.
Simple methods for determining and measuring distances on the ground, the eye method, according to the measured angular values of local objects, measuring steps, by ear.
The eye-measuring method is the basic, simplest and fastest, most accessible to everyone in any conditions. However, an accurate eye is not acquired immediately. It is developed through systematic training conducted in a variety of terrain conditions at different times of the year and day..
In order to develop your eye, you need to exercise as much as possible in determining the distance to the eye with the mandatory verification of their steps, on a map or in another way. Training should begin with short distances of 10, 50, 100 meters. Having mastered these distances well, you can go sequentially to large 200, 400, 800, 1000 meters. Then you can easily determine long distances..
The accuracy of the eye method is indicated and affected by such side effects as:
– Large-sized objects always seem closer than small ones located at the same distance.
– The less intermediate objects are between the eye and the observed object, the closer this object appears.
– When viewed from the bottom up, from the bottom of the mountain to the top, objects appear closer, and when viewed from top to bottom – further.
The glomerular distance estimation can be controlled when several people measure the same distance independently of each other. Taking the average of all these definitions, get the most accurate measurement. For a rough estimate of distances, sometimes use the approximate data shown in the table below.
Everyone can refine and supplement this table in relation to their observations. The accuracy of the eye method depends on the observer’s training, on the magnitude of the determined distances and on the observation conditions. For distances of up to 1000 meters, it is necessary to achieve training in determining the values with an error of not more than 10-15%.
The method of determining and measuring distances on the ground by the measured angular values of local objects.
If the linear value of the observed object (height, width or length) is known, then to determine the distance to it, it is necessary to measure the angle (in thousandths) under which this object is visible. And by the ratio of the linear (known in advance) and angular (measured) quantities of this object, using the thousandth formula, you can determine the distance to it.
The method of determining and measuring distances on the ground in pairs of steps.
When measuring distances in steps, you need to be trained in walking in even steps, especially in adverse conditions. On the ups and downs, when moving through a humid meadow, in a bush, etc. In addition, you need to know the length of your stride in meters. It is determined from measurement by the steps of the line, the length of which is known in advance and should be at least 200-300 meters.
When measuring distances, steps are considered pairs, usually under the left foot. After every hundred pairs of steps, the count starts again. In order not to lose count, it’s useful to mark each hundred pairs of steps taken on paper or bend your fingers in succession, or in any other way. Errors in determining distances in steps, with an even well-calibrated step, reach an average of 2–4% of the measured distance.
The method of determining and measuring distances on the ground in time and speed.
You can determine the distance by the time of movement, if you approximately know your average speed. So, for example, if the average walking speed is 5 km / h, when the ascents and descents are no more than 5 degrees, then after 45 minutes you can roughly say that you have traveled 3.75 km.
The method of determining and measuring distances to firing guns.
The determination of the distance to the firing guns is based on the detection, at the time of the shot, a flash and the formation of smoke. Then, knowing that the speed of sound propagation in air is 330 m / s, that is, rounded off 1 km in 3 seconds, we count the time in seconds from the moment of the flash to the moment of auditory perception of the sound of the shot (or explosion) and, dividing it by three, we determine the distance to guns in kilometers.
In the absence of hours, seconds can be counted by sequentially counting “to oneself” two-digit numbers (21, 22, 23, 24), starting from the moment of the flash from the shot until the sound comes from it. Counting each of these numbers takes about one second. Skills of such an account, commensurate with the move of the second hand, are acquired quite quickly after 2-3 trainings in counting two-digit numbers.
The method of determining and measuring distances by ear.
At night, in conditions of poor visibility, distances often have to be evaluated by ear. To do this, you need to be able to determine their sources by the nature of the sounds and know from what approximately distances you can hear these sounds at night. Under normal hearing and favorable acoustic conditions, the audibility range can be approximately considered as it is given in the table below..
These data vary depending on the specific conditions in which the observation is made, and therefore should be taken into account by each observer based on his personal experience..
Based on the book “Map and Compass My Friends”.