How to calculate distance
1) Take the map you are going to use to find the distance between two objects that interest you
2) Look at the scale (for example, 1:10 000, which means that 1 cm on map represents 10 000 cm in real life, or 100 m in real life)
3) Measure the distance between the points with a ruler in cm
4) Multiply this result (in cm) by 100
5) What you get is the distance in meters on surface of the earth.