### Layer Explorer

The Layer Explorer area of the Main Window shows all layers previously added to the project. To draw one or more layer at the Map Display, check its box and click on
The Spatial Reference System of the Map Display showed at the status bar is the first valid SRID among the layers checked. It is also possible to set a specific Map Display SRID by right-clicking over the Map Display area as explained here. To find out the layer-SRID, right-click over a layer name and choose Properties....
Each layer can be in one of the these status:

- box-checked

- selected

- box-checked and selected

- none

- disconnected () - when the data source containing the layer is disconnected or the location path changed. In this case right-click over the layer name and choose Change Layer Data Source. Then, use the edit option of the Data Source Explorer interface to reopen the connection in case of databases/database or to change the location path when the layer is a vector/raster stored in a directory tree structure.

Some actions at the Layer and at the Map Display depends on the layer status. Keep this in mind from now on and see how to select one or more layers at the Layer Explorer.

#### Layer Explorer - Selecting one or more layers

Clicking over a layer name makes it selected and the actions available from the context menu can be executed.
Right-clicking over a layer name makes it selected and shows a context menu of actions that can be executed over a layer. Those actions are also accessible through the Layer Menu.
Shift+clicking allows to select a consecutive set of layers by clicking over the first and the last layer names in the tree. A highlighted area appear in the tree and r ight-clicking over this area shows a context menu of actions that can be executed over more than one layer, for example Remove Layer(s).
Ctrl+clicking allows to select a non-consecutive set of layers by clicking over layer names in the tree. All layer names will became highlighted and right-clicking over one of them shows a context menu of actions that can be executed over all selected layer.
Note that the box-checked status is not necessary for some actions. For example, to execute Remove Layer, Show Table or Classification it is enough to select a layer.