I have just installed gvSIG because I need to convert a polyline feature (shape) into a polygons.
I used the sexante tool but I didn't get what I expected.
Basically I have an outer boundary (rectangle) and inside I have some ellipses and other polylines connecting on side of the boundary to another. It seems to me that the outer boundary is not recognized as a polyline. Indeed the polylines connecting two edges of the outer boundary are closed automatically after the conversion.
Can anybody help me on that?
This is the original image:
This is what I obtained after converting polylines into polygons with Sextante
> Hi everybody,
> I have just installed gvSIG because I need to convert a polyline feature
> (shape) into a polygons.
> I used the sexante tool but I didn't get what I expected.
> Basically I have an outer boundary (rectangle) and inside I have some
> ellipses and other polylines connecting on side of the boundary to another.
> It seems to me that the outer boundary is not recognized as a polyline.
> Indeed the polylines connecting two edges of the outer boundary are closed
> automatically after the conversion.
> Can anybody help me on that?
have you tried the "Polygonize" tool in SEXTANTE? This algorithm
converts lines to polygons, considering only the edges which describe
closed areas and without returning overlapping polygons. Hope this helps!
I can try but as long as I see from the attribute table of your attachment you just got 5 polygons while they should be 8. Probably you are missing polygons whose edges are both inner lines and part of the outer boundary.
See the image in the earlier messages that I produced with ArcInfo with a polygon highlighted in dark green. Do you have that polygon also in your map?
I have created 10 features with SEXTANTE "Create random vector layer"
tool and then applied both "Polygonize" and "Derivative geometries". It
seems that the results are quite different. The "derivative" polygons
overlap themselves, while the polygonized ones not. :-(
I'm agree with Fran. In this case, it seems that the external rectangle
doesn't intersect the internal lines at all, so it's surely a problem of
precision/snapping. SEXTANTE Polygonize tool nodes lines and merges them
using an enhanced precision in order to avoid topology exceptions,
however it doesn't snap "quite near" vertices. I think that we need more
robust topology checks in SEXTANTE and gvSIG in order to make them more
reliable and powerful in a production environment.
there are some vertices that need to be snapped on the "rectangle". Just
a trick: you could extend all internal lines in order to intersect the
external rectangle and then polygonize them. Sorry for my approximation,
but it's a topological problem that needs further investigation and I
haven't enough time to study it now.