Turning Layers On and Off and Making a Layer Active
Hopefully you've had a chance to take a look at the introduction to GIS Concepts section where we discussed layers.
Because there are often many layers available for a map, map layers are organized into related folders. When you initially open the map, some folders may be open and some may be closed. Likewise, some layers may be turned on while others may be turned off by default.To open a closed folder , click on it to open it . A list of all layers contained within the folder will be shown.
In this example a folder called "Terrestrial" has been opened and three layers are present one of which has been selected.
Similarly, you can click on an open folder to close it. Notice that opening and closing folders doesn't turn layers on or off; it simply helps you stay organized.
To display all available layers in a folder, click the small coloured rectangle . Clicking on the grey and white rectangle turns off all layers in the folder. It doesn't matter if a folder is open or closed when you do these operations.
A layer is 'on' (displayed on the map) when there is a tick in its tickbox .
Some layers are only available at certain scales. Layers that are available at the current scale will be shown with a tickbox that is open and can be selected. Layers that are not available are nevertheless listed but the tickbox has been greyed out .
To illustrate this
this layer is not available at this scale to be switched on for viewing.
Note that layers that are not available will also have a red asterisk next to them Clicking the red asterisk next to the name of an unavailable layer zooms you to the closest scale at which the layer is available. (Note although it will zoom to the scale there is no guarantee that that the object will be seen since it might now fall outside the geographical extends of the map window).
All BGIS maps have a similar file structure for opening different layers of information.
Let's open the "NSBA: layers" folder and the "Terrestrial" folder so it looks like the following
Now click on the "NSBA Terrestrial Ecosystem Status" Layer - if you have the Automatically Refresh Map ticked the layer will load and the Map will refresh itself. If the Automatically Refresh Map is not ticked you will need to tick the "NSBA Terrestrial Ecosystem Status" Layer AND "Refresh Map" buttonA layer is made 'Active' by clicking on the icon adjacent to a layer name . A light grey icon indicates that it is not active whereas a black icon denotes that it has been made active layer, and its name is displayed in the area below the map window. You can only have ONE layer active at a time.
In the above case "NSBA Terrestrial Ecosystem Status" has been made the ACTIVE LAYER.
So what does being an active layer mean? It means that the spotlight is on this layer. In other words, this is our way of telling the computer that this is the layer in which we are.