topic Re: Merge small polygons into larger units in ArcGIS Pro Questions

Dissolve / Pairwise Dissolve generates error

Mikhail — Sun, 11 Jun 2023 22:51:17 GMT

I have a shapefile with small polygons, that I need to merge into larger ones. Merging should be by a specific variable, conparid, which is available for any polygon. I am trying to use the 'Dissolve' and 'Pairwise dissolve' tools, but receive a message 'WARNING 000117: Warning empty output generated'. I successfully ran 'Repair Geometry' and 'Check Geometry', but this did not help.

Eventually, I simplified my dataset to include only two polygons, which I am trying to merge. Please see the screenshot attached. I wonder what could be wrong, and would appreciate any suggestions.

Merge small polygons into larger units

Mikhail — Sat, 10 Jun 2023 17:45:52 GMT

Hello,

I have a shapefile with small polygons, that I need to merge into larger ones. Merging should be by a specific variable, ConPar, which is available for any polygon. I tried the 'Aggregate Polygons' tool but it wants to merge all polygons within a certain distance and does not accept zero. In my case, polygons border each other. Could you suggest the right approach?

Re: Merge small polygons into larger units

LanceCole — Sat, 10 Jun 2023 18:22:15 GMT

Did you try the Dissolve Tool?

Re: Merge small polygons into larger units

Mikhail — Sat, 10 Jun 2023 18:51:16 GMT

Thank you! This looks like the right tool, but when I run it I get WARNING 000117: Warning empty output generated. I've also tried 'Pairwise dissolve' and ran into the same problem. Do you know what could have caused it?

Re: Merge small polygons into larger units

LanceCole — Sat, 10 Jun 2023 23:33:02 GMT

@Mikhail,

Without seeing your data and how you are running the tool, it is difficult to know why the error is occurring.

The input for the tool needs to be a feature layer
Check the geometry on the input feature
make sure the common attribute is actually the same
select a small number of features you know would be dissolved and test just those
look through the geoprocessing result and see if there are any addition errors
do you have write assess to the ourput location

Re: Merge small polygons into larger units

Mikhail — Sun, 11 Jun 2023 22:54:18 GMT

Thank you! I have tried all this, but nothing helped. I have even reduced my dataset to two neighboring polygons and tried dissolving them into a single unit...no luck so far.

Re: Dissolve / Pairwise Dissolve generates error

DanPatterson — Sun, 11 Jun 2023 23:02:47 GMT

do you have a csv file joined to the source table? Your dissolve field needs to be part of the input featureclass.

Also, dump the shapefile and make a featureclass in a geodatabase and do the dissolve on it.

If you need a shapefile after, then export it to one. It just removes a big place where things can go wrong.

Dissolve (Data Management)—ArcGIS Pro | Documentation

You just need Dissolve when things are properly structured for the input.

Re: Dissolve / Pairwise Dissolve generates error

DanPatterson — Sun, 11 Jun 2023 23:20:14 GMT

PS, don't repeat questions, they get merged in any event... just saves us time keeping things organized

Re: Dissolve / Pairwise Dissolve generates error

Mikhail — Sun, 11 Jun 2023 23:48:05 GMT

Dear Dan,

Sorry for duplicating my question, I did not know how the system works.

Thank you for your advice! You are right, I joined the csv table to a source table, and the grouping variable conparid was in the original csv file. Now I created a new variable 'merge' and set is equal to 'conparid' so that merge belongs to the input feature class. Unfortunately, nothing changed.

Could you please explain what you mean by dumping the shapefile. Where would it go?

Regards,

Mikhail

Re: Dissolve / Pairwise Dissolve generates error

DanPatterson — Mon, 12 Jun 2023 00:12:39 GMT

Copy Features (Data Management)—ArcGIS Pro | Documentation

shapefile as input

geodatabase featureclass as output

Then do the dissolve ensuring that all joins are permanent and you have a clean unjoined field to dissolve on.

Reverse copy features using the result as input and a shapefile as output... but skip shapefiles if you are using Pro (agol, arcgis api for python, or 3rd party aps may be exceptions),

there is no need for them now because of their limitations

Re: Dissolve / Pairwise Dissolve generates error

Mikhail — Mon, 12 Jun 2023 00:37:28 GMT

Fantastic, it all worked! The interesting thing is that the output of Dissolve looks very much like a shapefile. I can see the merged polygons on a map...I wonder why I did not have to do the last bit and convert the geodatabase to a shapefile?

Re: Dissolve / Pairwise Dissolve generates error

DanPatterson — Mon, 12 Jun 2023 06:51:01 GMT

Perhaps you could "Accept as Solution" the thread that provided the answer so that it can be discovered by others in your situation