Scale: Scale is the ratio of the length of a line segment on the map to the actual length of the corresponding line segment on the ground. The formula is: scale = the ratio of the distance on the map to the actual distance.
Legends and notes: Legends represent symbols of geographical things, and notes represent numbers and words of geographical things.
The two main features of maps are: 1 and testability caused by special mathematical rules. Special mathematical rules include map projection, map scale and map direction. 2. Use map language to express the intuition generated by things. All kinds of complex natural and human things represented on the map are realized by map language. Map language includes map symbols and map annotations.
Map language is very intuitive.