Dissolve to largest

Question

I would like to be able to do a Dissolve (which is quite easy ny itself) based on a singe attribute, but I want to dissolve the features to the largest adjacent polygon and retain all its attributes. In ArcView 3.3 there used to be a tool that could do so (Dissolve Adjacent Polygons), but I can't find anything useable for ArcGIS. Before I try to figure out how the ArcView tool works and translate it to VBA or Python, does anyone know if I'm overlooking a ArcGIS tool that does something similar?

curtvprice · Answer

I think that could do the trick. The only thing that I can't figure out is how to execute the merge based on the first feature. The only merge options I can find work with multiple datasets instead of the features in a single dataset. I can't find any useable options in the environments as well.

Sorry, I was wrong about the Merge tool in step 4. The field mappings work across one row at a time, not across multiple rows.

The tool you need to use instead of Merge is Summary Statistics (Statistics_analysis), specifying LAST for each field of interest (after the sort, LAST is the one with largest area) and dissolvepolyID as a case_field.

MarcelGlasbergen1 · Answer

I think that could do the trick. The only thing that I can't figure out is how to execute the merge based on the first feature. The only merge options I can find work with multiple datasets instead of the features in a single dataset. I can't find any useable options in the environments as well.

curtvprice · Answer

An approach I can think of is this:*  Dissolve your input by your single attribute
*  Run an Identity_analysis of your input against the dissolved output.
*  Sort (the tool, not just in table view) the identity output table by dissolvepolyID and area
*  Merge this sorted table using FIRST for your attributes. Use the field map control to name the output fields as you need to.
*  Join this result to your dissolve output table by dissolvepolyID