Active Layers

Vector and annotation layers in ENVI can be the selected layer, but for editing purposes they also need to be designated as the active layer. Specifying the active layer is necessary when you have multiple layers of the same type open, as it indicates the layer you want to edit. Vector and annotation layers are independent; if you have one or more of each layer type loaded, there will be one active vector layer and one active annotation layer.

ENVI tools are applied differently to vector and annotation layers, depending on the tool. Vector and Annotation tools work on the active layer, but the Transparency and Go To tools work on the selected layer, just as they do with imagery. The selected layer may or may not be the same layer as the active layer at any given time. For example, you may add new vector records to the active layer, then click to select a vector layer in the Layer Manager and apply transparency to that layer.

When working with active layers:

• When you create or load a new vector or annotation layer, it becomes the active layer for that layer type.
• To change the active layer for a layer type, right-click on a layer name in the Layer Manager and select Set as Active Layer or Set As Active Annotation Layer. The icon next to the active layer’s name is highlighted by a red box for vectors or a cyan box for annotations, and the right-click menu option Set as Active Layer or Set As Active Annotation Layer is disabled.
• When you have an active vector layer and an active annotation layer loaded and you are alternating between the two, select the appropriate tool button from the toolbar. For example, select a Vector tool if you want to edit the active vector layer.
• For vector layers, if you modified the active layer, ENVI prompts you to save the changes before you can set a new active layer. Save the changes if you want to keep them; otherwise, they are discarded.
• Reordering layers in the Layer Manager does not change which layer is the active layer. When you remove the active layer from the Layer Manager, another displayed layer automatically becomes the active layer.