A map is a scaled image of the area on which the objects located on it are plotted in topographic symbols: buildings, roads, paths, vegetation, hydrography, etc. on the ground, provided that they are mapped.
Determine the scale of the map. It is always indicated in its legend - the textual accompaniment of the map. This is the correspondence of the unit of measurement on the map to the distance on the ground. So, a scale of 1: 5000 means that 1 cm of the map is equal to 5000 cm or 50 m on the ground.
To determine the distance on the map, you need that those objects, the distance between which you are going to determine, were plotted on the map. The larger the scale of the map, that is, the smaller the number behind the one in the scale, the more detail the map has. So, if you need to determine the distance between buildings in the city, then you need maps of scales from 1: 2000 to 1: 10000, buildings are no longer displayed on maps of smaller scales. If the distances are between settlements, then you need maps with a scale of 1: 10000 and higher.
Find the objects on the map, the distance between which you will determine. If they are not indicated on the map, draw them yourself, taking into account their location on the ground. So, if you know that the object is located near a crossroads, find this crossroads on the map and mark it with a dot. If one of the objects is a mountain top, then find on the map the highest relief point in the area where this mountain is located.
Draw a straight line between two points and measure it with a ruler. Convert the centimeters measured on the map to the distance on the ground in accordance with the scale indicated on the map.