If you want to know the distance between two points in a straight line, measure the corresponding segment on the map with a ruler. Preferably, it was made from thinner sheet material. In the case that the surface on which the spread out map is not flat, to help tailor the meter. In the absence of a thin line, and if the card is not a pity to puncture, is convenient to use for measuring the compass, preferably with two needles. Then you can transfer it to graph paper and measure the length of line on it.
The road between the two points on the map are rarely straightforward. Measure the length of curved line will help the device - odometer. To use it, first roller rotation to align the arrow with zero. If the odometer is electronic, set it to zero manually is not necessary - just press the reset button. Holding the roller, press it to the starting point of the segment so that risk on the housing (located above the roller) was pointed right at this point. Then keep the roller on the line while the risk will be combined with the endpoint. Read the testimony. Be aware that some of the curvimeter there are two scales, one of which has a graduation in centimeters and another in inches.
Locate on the map pointer of the scale - it is usually located in the lower right corner. Sometimes this pointer consists of a segment of calibrated length, next to which shows to what distance it corresponds to. Measure the length of this cut line. If you find, for example, that it has a length of 4 centimeters, and next to it is specified that corresponds to 200 meters, divide the second number by the first, and you'll learn that each centimeter on the map equals 50 meters on the ground. On some maps instead of a cut there is a ready-made phrase, which may be, for example, as follows: "an inch is 150 meters." Also the scale can be specified as a ratio of the following type: 1:100000. In this case, it can be estimated that one centimeter on the map corresponds to 1000 meters on the ground, as 100000/100(inches per meter)=1000 m.
Measured with a ruler or odometer distance, expressed in centimeters, multiply by the specified on the map or the calculated number of meters or kilometers in one centimeter. The result is the actual distance, expressed respectively in meters or kilometers.