You will need
• A matchbox, a pencil, a ruler
Instruction
1
The most simple way to determine distance on the ground is associated with the use of eye. The main thing here – trained visual memory and the ability to mentally postpone into the visible area constant measure of length, e.g. 50 or 100 m. Fix memory benchmarks and compare them the distancethat you should measure on the ground. One of the simplest standards, the distance between the electricity poles, which is usually about 50 m.
2
Measuring distance by mental snooze permanently, keep in mind that the local objects will appear to be reduced according to remove them. In other words, if you delete two times the object seems to be twice smaller.
3
When using the eye keep in mind that in conditions of poor visibility (fog, dusk, cloudy weather, rain, etc.) objects seem to be located farther than the really are. The accuracy of this method primarily depends on the training of the observer. A common mistake in distance in kilometer is about 15%.
4
Use the method of determining distances on the linear dimensions. To do this, take a ruler and hold it at arm's length. Measure with a ruler in millimeters viewable width (height) of the objectto which the measuring distance. The actual width and height of the object, known to you, turn to centimeters, then divide by the apparent size in millimeters, and multiply the result by 6 (a constant value). The result is the required distancem from the object.
5
The third way to determine distance on the ground – the angular size. This requires to know the linear size of the object (length, height or width) and the angle in mils, at which the observed object is visible. With this background, determine a distance to the object according to the formula:D = L x 1000 / A;where D is distance to object; L — linear size of object; A — the angle at which the visible linear size of the object; 1000 is a constant.
6
For determining the angular magnitude should know that the segment length of 1 mm, located at a distance of 50 cm from the eye will correspond to the angle of 2 mils. Accordingly, for a length of 1 cm the angular size is equal to 20 thousandths and so on. Remember the angular size (in thousandths) of some available tools:the thumb (thickness) – 40;
Pinky (thickness) – 25;
Pencil 10-11;
Matchbox (width) – 50;
Matchbox (height) - 30
Match (thickness) – 2.