i am trying to merge multiple polygons of a feature. i select them via select features by polygon and use the advanced digitalizing toolbar " merge selected features" option. it worked for some but mostly i get: error occurred during merging operation.
[GIS] merging shapefiles . an error occured during the merge operation
polygonqgis
Related Solutions
There's a couple of ways of going about this but you probably want to dissolve the features (Vector->Geoprocessing Tools->Dissolve). With dissolve you don't need to select anything first as it is all done from the attributes. So, let's say you have a field called 'Type' (for example). Then in your example your polygons would all be type 'A' (and you could have some other polygons of type 'B' which you don't want to join with ones of type 'A'). If you select the 'Type' field (or other appropriate attribute in your case) as the attribute to dissolve on then all features of the same type will join together (internal boundaries will be dropped). This may well result in a multipolygon (a single feature which has more than one part, like an archepelago), which might or might not be acceptable. If it is undesirable then simply split the feature up into its constituent polygons by using Vector->Geometry Tools->Multipart to Singlepart.
The alternative is to buffer your polygons by zero, but this probably will join polygons of different types together where you don't want it to happen, so dissolve (optionally follwed by multipart to single part) is safer.
You didn't specify it in your question but it looks like you are using QGIS.
The "Split selected feature with select line from another layer" tool is from the Digitizing Tools plugin. You may need to download/install from the toolbar menu:
Plugins > Manage and Install Plugins
Once installed and enabled, it should show up in the toolbar. If not then right-click anywhere on the toolbar and you should see the option to enable it:
The icon for the "Split selected feature with select line from another layer" tool is this one:
Best Answer
I find that it sometimes gets confused if there are too many nodes on shared lines between features. Chack the geometry validity of the features too because geometry errors can cause problems. Also you could try adding features one by one and not trying to merge all of them together at the same time, if it isnt too time consuming