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Selecting Layer control will add a Layer control to the map with a Legend. You can decide how much information you wish to add to this control and whether or not you want it to be displayed by default. Also if you select images only for the Legend this will mean that users cannot turn the Layers on and off.
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If you leave the Open by default unticked but you have selected to display the Layer control then you will see the following Legend button (top right of map) which, when clicked, will display the Layer control.
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