Dissolve polygons

Q: How to dissolve vector polygons (or remove tile boundaries of adjacent maps)

A: Dissolving of areas is done with v.dissolve (v.extract -d). If tile boundaries of adjacent maps (e.g. CORINE Landcover SHAPE files) have to be removed, an extra step is required to remove duplicated boundaries:

Remove duplicated tile boundaries:

    v.clean clc2000_patched out=clc2000_clean tool=snap,break,rmdupl thresh=.01
  

No longer needed in GRASS > Version 6.4: Reclass based on desired column:

    v.reclass clc2000_clean out=clc2000_recl col=CODE_00

Dissolve:

    v.dissolve input=clc2000_recl output=clc2000_final

    v.dissolve input=clc2000_clean output=clc2000_final