* Martino <[email protected]> [2017-09-28 13:52:25 +0100]:
Ciao Martino,
I have a vector layer containing polygons that represent vegetation patches. There are 15 vegetation types (and most have more than one polygon; i.e. the polygons are multipart). Some of the polygons overlap as the areas have more than one classification (e.g. a polygon representing one plant species and a polygon representing another plant species).
Can you derive as many independent layers as the number of vegetation types? Manually or better with a small script.
I would like to produce a new layer in which all of the overlapping areas become new polygons. For example, an area of overlap of a patch of Species A and a patch of Species B would become a new polygon representing areas containing both species (and the non-overlapping areas would become separate polygons).
I think having independent layers would be the basis to work on and produce the kind of combinatory polygons you are aiming at.
So I start with Polygon with Species A Polygon with Species B and the result would be Polygon with only Species A Polygon with only Species B Polygon with Species A & B I am unable to figure out how to do this! If anybody has any suggestions, I would welcome them. With thanks.
If you have Polygon "A" and Polygon "B", then look after geoprocessing operations. For example, 'Intersection', Union', and the likes should give what you are looking for. Alternatively, if you could work with raster maps, you can think of having raster maps for each individual vegetation type, then combine the maps based on some classification scheme that does include combinations of vegetation types. Say vegetation type A is going to be assigned a pixel value of 1, vegetation type B is going to get a pixel value of 2 and then a pixel occupied by A and B is goint to get a pixel value of 3. This is an idea to approach the question. Regards, Nikos
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