This article looks at how to merge shapefile polygons using Quantum GIS. you can download Quantum GIS from Here. We demonstrate the merging using an example. We have a France shapefile that shows all the regions in France. We want to merge all the regions and create a single shapefile for France. Here are the steps.
1. Open Quantum GIS Desktop.
2. Add the existing France shapefile using the ‘Add Vector Layer’ button as show below.
3. This is how the France KML looks. Note the individual polygons for regions.
4. To merge the polygons select Vector->Geoprocessing Tools->Dissolve.
5. Select the variable that will be used to merge the polygons. The variable should uniquely identify each polygon.
6. Give the path and name of the output shapefile and hit OK. Once the progress bar reaches 100%, the application will ask whether you want to load the merged polygon. click on yes. Close the dissolve window. That’s it!