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On QGIS, I have a worldwide basemap on which I selected Australia and I saved this selected layer.

Now, I would like to increase the size of my layer while keeping the continent boundaries and the proportions. It means that my layer Australia will be a little bit bigger than the "original" Australia from the basemap.

Attribute table

Layer tree

Screenshot of the map

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5 Answers 5

10

You can use "Vector Geometry > Geometry by Expression" tool with the following expression. Just specify scale_x and scale_y.

with_variable( 'dx',  x(centroid($geometry)),
  with_variable( 'dy',  y(centroid($geometry)),
    translate(  
      affine_transform(
        translate($geometry, -@dx, -@dy),
        delta_x:=0,
        delta_y:=0,
        rotation_z:=0,
        scale_x:=1.05,
        scale_y:=1.05),
      @dx,
      @dy
    )
  )
)

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6

You can use the SAGA Transform Vector Layer available in your toolbox.

Your size can be changed accurately by the "Scale factor" properties for both dimensions, as per below:

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6

Another possibility (this one has an effect only on symbology level, some of the other answers will either modify the actual feature or create a new layer with an enlarged shape, choose the solution accordingly) is to activate the draw effect and select the transform effect (where you can modify x and y size independently, rotate or translate your shape)

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4

Two options spring to mind:

a) Why not just buffer it? Go to 'Vector' --> 'Geoprocessing tools' and select the 'Buffer' option. Set a distance that seems suitable for you.

b) Changing the outer boundary offset: Right click on your layer and go to 'Properties' --> 'Symbology'. Click on your symbol and change it to "Outline: Simple line" and change the "offset" option according to your wishes. This option does not change the polygon's size but just changes its' appearance.

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  • 1
    Thank you very much for your help. I am new to QGIS. When I click on "Vector", nothing happens. And your other solution is a good idea but I would like to fill my layer with colors.
    – Ambre
    Feb 15 at 8:36
  • 1
    Research buffering on the QGIS help pages. If clicking on 'Vector' in the upper toolbar really does not open a drop-down menu of your tools you can also use the 'Processing toolbox' to call it. Right click on the upper section of the toolbars (above your map) --> a drop down menu should open. Select the 'Processing toolbox' it should now dock on your workspace. Using the 'Search...' field call the 'Buffer' algorithm under 'Vector geometry'. If you don't know how to do this try one of the many youtube videos on buffering etc. That often helps.
    – Niklahrs
    Feb 15 at 8:44
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You can change the size of the polygon by activating the 'advanced shape digitizing' toolbar (1.). Right click anywhere in the panel with all the small symbols. Then activate layer editing (2.) and click on the symbol for scale (3.). You can set the base point for the scale with 'crtl + left click' and either drag it or enter a scale factor. In the same toolbar, you can also find tools to move the polygon around.

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