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How to enlarge a polygon with centroid in QGIS?
Run Centroid, using input polygon_layer. Here’s an example, with the centroid labelled using the expression x ($geometry)||’ ‘||y ($geometry). Scale Factor X/Y = the coefficient you want to enlarge by. In this example, I’ve specified a scale factor of 2 for both, meaning my output will be double the size of the input.
How to construct a polygon from a point?
A better way to construct a polygon from points is to use PostGIS’ geometry constructors. This way, you avoid the need to convert binary → text → binary ( WKB → WKT → WKB ), which is slower, lossy, and is prone to text formatting distractions as evidenced by the missing ||. For example, try: Good!
How to prevent a polygon from drifting in QGIS?
In order to prevent your shape from “drifting”, you’ll need to derive the centroid first. Run Centroid, using input polygon_layer. Here’s an example, with the centroid labelled using the expression x ($geometry)||’ ‘||y ($geometry).
How to enlarge a polygon without changing its shape?
Both GRASS (as Erik Lohmann points out) and SAGA have tools that can accomplish this. I’ve accomplished this in the past using the tool SAGA > Vector General > Transform vector layer. In order to prevent your shape from “drifting”, you’ll need to derive the centroid first.
How to have different layer styles at different scales in QGIS?
It looks like this when you zoom in and out : keep in mind, that when you zoom out of the defined zoom levels, the layer won’t be shown. To have different styles within a category you can refine the rules by right-clicking on a rule -> Add scale and set different scales.
Is there tool in QGIS where I can do this task?
I tried to use the vector affine transformation plugin, but whenever I try to change the size of the polygon, the whole layer changes its position and shape. Is there a tool in QGIS where I can do this task or is it possible with the affine transformation plugin and I just cannot find the right values?
Which is the best algorithm for smoothing polygons in QGIS?
Beside this you can use the Douglas-Peucker algorithm in PostGIS too, so you can use it PostGIS then adding the PostGIS layer to QGIS. you can find some info here about Simplify: Reduce the weight of a geometry. Aragon’s answer is good for generalization.