I have a layer of regions (25 regions) and a layer with thousands of polygons. I want to dissolve this into one polygon for each region (so I can calculate the exact geometry). I used the dissolve tool of ArcGIS, but using this dissolves it into one layer. Is there a trick for this? Can't seem to see it in the dissolve tool itself.
You should be able to do that by using two tools, Dissolve and Split:
- First of all, add field for region in polygon attribute table. This field must be text-type.
- After that, dissolve your polygon layer but remember to check Create multipart features (it is optional) but by default it is checked.
- Finally, split same region in different layer by Split(Analysis) tools in Arctoolbox in specific Workspace. Split Field in Split(Analysis) is the field region you had created already.
You can also try the Union tool to combine your region and polygon layers (it will split polygons that lay across region lines and assign the appropriate attributes to each piece although area fields will have to be recalculated) and then dissolve on the region.