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I am using QGIS and have a shapefile of the blocks in a large city, where each polygon is a particular streetblock. The city is divided into various sectors, and each block has information on its sector. I can easily classify the blocks by this attribute to visually inspect the shape of these sectors:

sectors

The issue is that the gaps between the blocks is the road network. I would like to dissolve all blocks in the same sector into a contiguous polygon, but am unsure how to do this.

Does anyone know an easy way to "fill in" the gaps between the city blocks in order to make the dissolve work properly?

  • Convert polygons to lines and again from lines to polygon. Before that, an outer boundary to enclose all the polygons has to be created. Problem with this method is, you have to manually merge the polygons of same id unless the road line has any similar id/attribute w.r.t polygons. Another option is, you can try "Fill Holes" in QGIS (Processing toolbox) if the coordinate system is a projected one. Will be easy if you know the "max_area" distance in meters rather than in decimal degrees (100 meters apprx 0.001 degrees) – joseph_k Jan 10 '18 at 5:26
  • This might be helpful. gis.stackexchange.com/questions/164296/… – joseph_k Jan 10 '18 at 5:28
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    How about creating a convex-hull for each sector, then merge with this with all the other polygons in that sector. – Cushen Jan 10 '18 at 6:42
  • I was able to successfully generate the convex hulls of these sectors, but the problem is that these hulls don't adequately depict the odd shapes of the sector boundaries, and places many of the blocks outside of these new polygons. Since I want to eventually measure the distance of the blocks to the boundary, this gives me negative distances. – Obie K Jan 10 '18 at 16:42

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