Topological editing

Topological editing

Besides layer based snapping options the General tab in menu Settings -> mActionOptionsProject Properties... also provides some topological functionalities. In the Digitizing option group you can Enable topological editing and/or activate Avoid intersections of new polygons.

Enable topological editing

<P> The option Enable topological editing is for editing and maintaining common boundaries in polygon mosaics. QGIS "detects" a shared boundary in a polygon mosaic and you only have to move the vertex once and QGIS will take care about updating the other boundary.

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Avoid intersections of new polygons

<P> The second topological option called Avoid intersections of new polygons avoids overlaps in polygon mosaics. It is for quicker digitizing of adjacent polygons. If you already have one polygon, it is possible with this option to digitise the second one such that both intersect and qgis then cuts the second polygon to the common boundary. The advantage is that users don't have to digitize all vertices of the common boundary.

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