Omission

The difference between "selection" and "omission" is sometimes confusing.
As seen previously, selection is the choice of which information will be necessary to carry out the purpose of the map successfully, so the choice of which types of information to include on a map. Whereas, leaving out the excess information from a given class is selective omission.

Omission Example

What happens to the houses if we go from a large scale to a small scale? Can we keep all of them or should we omit some? Roll over the different scales to get a view of the representation of houses varying with scale.

Source: IKA, according to (Schweizerische Gesellschaft für Kartographie 1975)

Omission and Map Character

When omitting objects, the original character should not be changed in its essence.
The original form, size and spaces should be maintained despite the decreasing number. The following animation gives you some graphical advice to keep the original character, when representing houses at different scales

Source: IKA, according to (Schweizerische Gesellschaft für Kartographie 1975)

Self Evaluation about Omission

Test your knowledge of the omission process. In the following built-up area map, the red squares represent houses. You have to generalise it (double scale). Find the ideal house placement for the new map by dragging and dropping (left continuous click) the left black square (houses at the new scale) next to the map.

Source: IKA, according to (Schweizerische Gesellschaft für Kartographie 1975)