I have a set of polygon layers with thousands of polygons some of which are adjacent (Either rings or simply adjacent). I would like to simplify this polygons by merging them.
Is there a way to do this automatically?
[GIS] Merging adjacent polygons in QGIS
adjacencylayersmergepolygonqgis
Related Solutions
A topological vector model will provide what you need. In a non-topological storage (such as a shapefile), a single edge between geometries is stored twice. In a topological vector, the areas are stored separately from the lines, so adjustments can be made without effecting topology. I couldn't find a good diagram, so I created this simple example, where the areas A, B and C are computed from the intersections of the lines (connecting 1-4) which separate them.
This model is used by ArcInfo as coverages, in GRASS as its default vector model, and can be used in PostGIS with the experimental PostGIS Topology tool. Perhaps a simpler solution is converting your data into linework, removing the redundant segements, and then recreating your polygons after simplification.
I would use the Dissolve tool for this task. As it is described in the help it should dissolve your polygons the way you need it. You can select a Dissolve_Field which in your case should be the attribute with the landcover type.
Remember to check or uncheck the multipart feature box depending if you want to have separate polygons or only one with multiple parts.
Best Answer
You could ask the dissolve tool which you can select through the Vector tab, then Geoprocessing tools.
Then select the dissolve tool to open and input the dataset
You could also refer to QGIS documentation