Dissolve (merge geometries)

configuration-examples Dissolve

Dissolving is the process of merging detailed polygon geometries in larger polygon geometries by removing interior segments.

In the GeoDMS this can also be done based on a relational attribute to make polygons for each entry of the domain-unit of this relational attribute.


container dissolve
   unit<float32> meter    := baseunit('meter', float32);
   unit<fpoint>  point_rd_base;
   unit<fpoint>  point_rd := 
      range(point_rd_base, point(300000[meter],0[meter]), point(625000[meter],280000[meter]));

   unit<uint32> municipality
   : StorageName      = "%SourceDataDir%/CBS/2017/gem_2017.shp"
   , StorageType      = "gdal.vect"
   , StorageReadOnly  = "True"
      attribute<point_rd> geometry (polygon);
      attribute<string>   name;
      attribute<string>   regionname;
      attribute<region>   region_rel := rlookup(regionname, region /values);
   unit<uint32> region := unique(municipality/regionname)
    attribute<point_rd> geometry (polygon) := 
        partitioned_union_polygon(ipolygon(municipality/geometry), municipality/region_rel)[point_rd];


The example presents two domains: municipality and region. A relation is configured (region_rel) relating the municipality domain unit to the region domain.

The actual dissolving is done in the bold line. The partitioned_union_polygon is used to dissolve the geometries of a municipality for a region. The ipolygon conversion function is used as these vector functions only work on integer coordinates. The casting back to [point_rd] at the end of the expression is used to convert the integer coordinates back to the point_rd values-unit.