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I'm looking to manually skew the shapes of areal polygons, but need to ensure their areas are not altered. Is anyone aware of any GIS tools or programming workflows that exist for manually reshaping spatial polygons while preserving areas? I wonder if there is an approach that utilises anything like the force-directed algorithms used in graph drawing. Grateful for any advice.

  • Do you use a specific software? – julien Aug 12 '13 at 13:16
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    The most general way is to warp the feature any way you like and afterwards rescale it to match its original area. That is too much freedom for most applications, which is why I am encouraging you to share with us any constraints you would like to impose on the warping process or the resulting shapes. – whuber Aug 14 '13 at 15:54
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    @Nikos Sure, plenty. Rescaling is one form of affine transformation, making it a key tool for registering geographic data. It can be used to enforce area constraints, as suggested in my previous comment, without changing the actual shape of a figure: rescaling merely changes the size. – whuber Nov 20 '13 at 13:00
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    @whuber, Fortunately for GFOSSers, QGIS has a plugin for that (coded by Mauricio de Paulo) called... well Affine Transformations :-) – Nikos Alexandris Nov 26 '13 at 22:21
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    I'd like to test these suggestions and demo the workflow, but no time right now. Happy to close off now if people would prefer. – geotheory Nov 26 '13 at 23:33

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