Dissolving a map

This operation dissolves objects of a layer based on specified attributes. Objects with the same value for the specified attributes will be part of the same group.

The output is a new layer that contains an object for each group identified in the input layer.

The geometry of each group is the result of the spatial UNION of all objects geometry dissolved to that group.

The attributes of each group are composed at least by all attributes used to dissolve, an ID, and a new one called NUM_OBJ to register the number of objects used to generate the group. Besides that, some attributes can be chosen to be summarized using the following statistical parameter:

For numerical properties: MINIMUN VALUE, MAXIMUM VALUE, MEAN, SUM, TOTAL NUMBER OF VALUES, TOTAL NUMBER OF NOT NULL VALUES, STANDARD DEVIATION, VARIANCE, SKEWNESS, KURTOSIS, AMPLITUDE, MEDIAN, COEFFICIENT OF VARIATION and MODE;

For text properties: MINIMUN VALUE (lexicographical), MAXIMUM VALUE (lexicographical), TOTAL NUMBER OF VALUES and TOTAL NUMBER OF NOT NULL VALUES


Click on PROCESSING → VECTOR PROCESSING → DISSOLVE.


Select the layer to execute the operation.

A list of layer columns will be presented and choose which ones will be used to dissolve the map.

Optionally use Filter with part of the attribute name to filter the attributes displayed.

Optionally, check the option Only selected if you wish to process only the objects that are selected in the map display.

Optionally, check the option Calculate Statistics if you wish to calculate some statistical summarization over other attributes not used in the aggregation.

Select one type of repository by clicking on the button to save the output layer as a file or on the button to save it in the database.

Enter the name of the output layer and click on the OK button.

In the example all the polygons with the same folnome column were dissolved and presented in a new layer with four polygons.



Depending on the size of the map processing error may occur and can be seen in the log viewer (PROCESS → LOG VIEWER)


Note: In case of memory error some alternatives can be used: add more columns to dissolve in smaller areas.