I classified raster dataset and converted raster dataset into polygon shapefile, then merged adjacent grid polygons using QGIS Dissolve function (figure 1) creating a temporary file. However, when I try to export it into a shapefile some holes in polygons are automatically filled (figure 2) which I don't want as I will use those holes in my further analysis.

How do I dissolve polygons without filling the gaps using QGIS?

  Figure 1 (Temporary file)                   Figure 2 (After saving)

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  • Can you upload the raster to do testing with it? – ImanolUr Aug 29 at 13:28
  • Polygonizing a raster almost always creates some invalid geometry, which you should fix before exporting the layer. For example, in the bottom left corner of the first image, notice that there are either two polygons whose corners touch (this is OK), or one polygon with intersecting vertices (this is invalid). Also at the top-center you have intersecting vertices. – csk Aug 29 at 16:52

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