# Measurement of distances and ranges by the sound and flash of a shot or explosion, by the linear size and angular value of the object, determining the width of the river.

The determination of distances and distances from the sound and flash of a shot or explosion is as follows. The time from the moment of flash to the moment of perception of sound is determined and the range is calculated by the formula D = 330t, where D is the distance to the place of the flash, meters, and t is the time from the moment of the flash to the moment of perception of sound, seconds. In this case, the average speed of sound propagation is taken equal to 330 m / s.

## An example of determining distances and ranges from the sound and flash of a shot or explosion.

The sound was heard 10 seconds after the flash. The distance to the place of the explosion is 3300 meters.

## Measurement of distances and distances by the linear size and angular value of the observed object.

If the linear value (height, width or length) of an object is known, then by the angle under which this object is visible, you can determine the distance to it using the thousandth formula:

## D = 1000V / U

where D is the distance to the subject in meters.
B – linear size of the item in meters.
Y – the angular value of the item in thousandths.

The angular value of an object is measured with binoculars, a ruler with millimeter divisions, or some improvised object, the angular dimensions of which are known. The linear dimensions of some items are shown in the table below.. ## An example of measuring distances and distances according to the linear size and angular value of the observed object.

The angular value of the length of the tank (7 meters), determined on a binocular scale, is 0-10. Distance to the tank:

## Speedometer and distance measurement.

According to the speedometer, the distance (length of the route) is determined as the difference between the readings at the final and initial points. The accuracy of determining the distances by the speedometer depends on the conditions of adhesion of the wheels (tracks) to the ground, wear of the treads, and tire pressure. When driving on a highway and solid ground, the error does not exceed 3-5% of the distance traveled.

If the speedometer readings deviate from the actual distance traveled by the machine, more than 5%, it is recommended to introduce the appropriate correction into the measurement results, which is determined by the car’s driving along the road typical of this route. The length of the road section selected for speedometer control is determined by kilometer posts or a map. In the latter case, the road should be straight and not shorter than 10 km.

## Measuring distances and ranges by measuring steps.

When measuring distances, steps are considered pairs. A couple of steps can be taken on average for 1.5 meters. For more accurate calculations, the length of a pair of steps is determined from measuring by steps of a line of at least 200 meters, the length of which is known from more accurate measurements. With an equal, well-calibrated step, the measurement error does not exceed 5% of the distance traveled.

## Determination of the width of the river, ravine and other obstacles by building an isosceles right triangle.

Point A is chosen near the river (obstacle) so that on its opposite side any landmark B is visible and, in addition, along the river it would be possible to measure the line. At point A, restore the perpendicular AC to the line AB and in this direction measure the distance (with a cord, steps, etc.) to point C, at which the angle of the ACB will be 45 degrees. In this case, the distance of the speaker will correspond to the width of the obstacle AB. Point C is found by approximation, measuring the angle of the ASV several times using any available method. For example a compass, using a watch or eye.

Based on the materials of the book “Handbook of Military Topography”.
A. M. Govorukhin, A. M. Kuprin, A. N. Kovalenko, M. V. Gamezo.