The ability to correctly and quickly measure angles on the ground may be necessary if it is necessary to determine the distances to inaccessible objects, measure their length, width or height. For example, when determining the width of a river or other obstacle, the height of a tree, in calculating the remaining path to the final goal. As a rule, the thousandth formula is used..
Measurement of angles on the ground using a compass, the dial of a watch, binoculars with a scale, using a ruler and eye measurement of angles.
The compass sighting device is preliminarily combined with the initial stroke of the limb, and then it is sighted in the direction of the left side of the measured angle and, without changing the position of the compass, the countdown is taken against the direction of the right side of the angle. This will be the value of the measured angle or its complement up to 360 degrees (60-00), if the signatures on the dial go counterclockwise.
The angle of the compass can be determined more accurately by measuring the azimuths of the directions of the sides of the angle. The difference in azimuths of the right and left sides of the angle will correspond to the value of the angle. If the difference turns out to be negative, then it is necessary to add 360 degrees (60-00). The average error in determining the angle in this way is 3-4 degrees.
Measuring angles on the ground by the watch dial.
The dial is held horizontally in front of you and rotated so that the stroke corresponding to 12 hours on the dial is aligned with the direction of the left side of the corner. Without changing the position of the clock, they notice the intersection of the direction of the right side of the corner with the dial and count the number of minutes. This will be the angle in large divisions of the goniometer. For example, a countdown of 25 minutes corresponds to 25-00.
Measurement of angles on the ground with binoculars with a scale.
The extreme stroke of the scale in the field of view of the binoculars is combined with an object located in the direction of one of the sides of the angle, and without changing the position of the binoculars, the number of divisions to the object located in the direction of the other side of the angle is calculated. The resulting number is multiplied by the price of the scale divisions (usually 0-05). If the binocular scale does not completely capture the angle, then it is measured in parts. The average error in measuring the angle with binoculars is 0-10.
Measure angles on the ground using a ruler.
If the ruler is kept at a distance of 50 cm from the eyes, then a division of 1 mm will correspond to 0-02. When the ruler is removed from the eyes by 60 cm, 1 mm corresponds to 6 minutes, and 1 cm to 1 degree. To measure the angle in thousandths, a ruler is kept in front of you at a distance of 50 cm from the eyes and the number of millimeters between objects indicating the directions of the sides of the angle is counted. The resulting number is multiplied by 0-02 and get the value of the angle in thousandths.
To measure the angle in degrees, the procedure is the same, only the ruler must be kept at a distance of 60 cm from the eyes. The accuracy of measuring angles with a ruler depends on the ability to make the ruler exactly 50 or 60 cm from the eyes.
Glazomerny determination of angles on the ground.
The glomerular determination of the angles on the ground consists in comparing the measured angle with the known one. Angles of a certain size can be obtained in the following ways. A right angle is obtained between the direction of the arms, one of which is stretched along the shoulders, and the other is directly in front of you. Some part of it can be postponed from the angle compiled by such a technique, bearing in mind that 1/2 part corresponds to an angle of 7-50 (45 degrees), 1/3 corresponds to an angle of 5-00 (30 degrees), etc..
An angle of 2-50 (15 degrees) is obtained by sighting through the thumb and forefinger, placed at an angle of 90 degrees and 60 cm from the eye, and an angle of 1-00 (6 degrees) corresponds to the angle of sight for three closed fingers: index, middle and nameless.
Based on materials from the Handbook of Military Topography.
A. M. Govorukhin, A. M. Kuprin, A. N. Kovalenko, M. V. Gamezo.