I use QGIS. I have two shapefiles with the administrative boundaries in two differnet years. These boundaries have changed: some wards (smallest administrative area) remain the same, some are newly established (carved out), others have been combined.
I now need to keep track of these changes: I need to know which of the wards have remained the same, which have changed and in what way. I also need the attribute tables as they contain all the codes (and they have changed as well so I need to know which old code refers to a new code).
I used the Geoprocessing tools (union, intersect, symetrical difference) but the results are rather useless as there are many sliver polygons.
I looked at Analyzing differences between two shapefiles to put results into new shapefile? that seems to be similar but does not give me an answer I can work with.
Since I am a beginner with QGIS I am not really sure where my problem lies. Maybe the geoprocessing tools would work if I did not have the problem of sliver polygons (I have the suspicion this is the case). So now I tried to get rid of the slivers (Vector-Geoprocessing-Eliminate...) - but I get the message "could not eliminate features with these ids:" following a list of all my ids.
What did I do wrong?