A layer is a group (g element) of elements identified by an ID

Layers are useful to organize large drawing by grouping elements by theme.

They are used traditionally in cartophic maps to separate roads, buildings, utilities networks.

Layers are defined as children of the document root element.

Layers can also be defined as children of layers as needed.

The document root element is identified as the default layer (named root).

One layer is defined as the input layer to object creation, selection and edition.

The input layer can be selected from the menu bar :

Layers functions are available from their dialog panel identified by it's icon

The layers dialog panel offers full features:

Figure 3.13. Layers dialog panel

See showcases manage layers , style layers and change object layer for a full features demonstration.