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    By David Crowther

    QGIS___How_to_Re-Order_Objects_in_the_Map_-_1.PNG

    Question:

    I have multiple objects at the same location. Is there a way to re-order the map objects based on an attribute?

     Answer:

    Yes – by using Thematic Styling we can then apply Symbol Levels to each Category to effectively change the order that objects are drawn in the map.

    For example, here we have a Planning Applications layer:

    QGIS___How_to_Re-Order_Objects_in_the_Map_-_2.PNG

    At certain locations if we use the Identify Tool we can see that there are multiple features/records on top of each other. Here we have two planning apps, one has its Progress set to ‘Passed’ and the other ‘Declined’.

    QGIS___How_to_Re-Order_Objects_in_the_Map_-_3.PNG

    If we now apply a Thematic Style to this layer using the Progress value, we can show the features with these colours:

    • Passed = Green
    • Submitted = Blue
    • Declined = Red

    QGIS___How_to_Re-Order_Objects_in_the_Map_-_4.PNG

    However, at the Derby Hall location where we have two planning apps on top of each other, you may wish to show the record with the Progress equal to ‘Passed’ on the top. Currently it is displaying the Declined Planning App.

    To do this in the Layer Properties > Symbology > choose Advanced > Symbol Levels:

    QGIS___How_to_Re-Order_Objects_in_the_Map_-_5.PNG

    Tick to Enable Symbol Levels and then define the order that you wish features to be drawn within the map window by giving them a numeric draw order.

    QGIS___How_to_Re-Order_Objects_in_the_Map_-_6.PNG

    Note – The order will determine the order in which they are drawn first. So if you want the ‘Passed’ features to be on top they should be drawn last e.g. the value 4.

    Once you have applied the changes to the map, notice how the map objects are now re-drawn using a symbol level determined by a value in your data:

    QGIS___How_to_Re-Order_Objects_in_the_Map_-_7.PNG