The method of the thumb. Definition of distance
In order to develop a good eye, one should constantly exercise in determining the distances, often measure by eye and with the help of calculations, determine the steepness of the slopes, the width and speed of the flow of rivers, etc., for example, in hunting or walking, any surrounding objects and check it with steps. And the more such tasks the hunter decides, the better. Good, experienced hunters, as is known, determine the corresponding distances with very high accuracy.
Let's say that you need to measure the distance to the pedestrian. In this case, it is necessary to pull forward the hand with the raised thumb and close one eye (the right eye closes when the pedestrian moves from right to left). At the moment when the pedestrian will cover with a finger, you need to close your left eye and open the right one. The pedestrian will seem to be pushed back.
Now you need to count how many steps the pedestrian will have time to make until the moment when he again covers his finger. The distance to the pedestrian will be equal to the number of steps multiplied by 10. Suppose that he managed to make 16 steps: 16x10 = 160 steps. If, at the same time, it is assumed that the human step is equal to an average of 0.75 m, then to a pedestrian 120 m.