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I was part of a project recently where handheld GPSs were used to collect vertices of parcels. After plotting the points using 'P2One' plugin in QGIS I found out that some of the polygons were twisted due to the fact that the vertex points were not collected in a clock-wise or counter-clockwise manner. The 'P2One' plugin uses the time stamps for each point on the GPS data collected to determine the sequence with which to plot points collected for a parcel.

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Is there a tool or script in QGIS that can help correct the twisted polygons to regular shapes automatically?

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Do all your parcels have four sides? In which case you can take the convex hull of the points and that will sort out the geometry for you.

Example:

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Then use the Convex Polygon processing tool, and make sure you create "convex hulls based on field" by some unique ID for each of your parcels, or you end up with the convex hull of your whole layer:

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Result:

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  • Many thanks Spacedman, it worked. Though all the parcels for the area are not 4 sided, this technique will save me time for the twisted ones.Thanks again – Kay May 27 '16 at 4:56

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