Dissolve

The dissolve operation aggregates vector features based on a shared attribute value, merging their geometries into single features and optionally computing summary statistics for numeric fields. Internal boundaries between features with the same attribute value are removed, producing a simplified output with fewer, larger features.

Dissolve takes an input feature layer and a dissolve field (the attribute used for grouping). All features sharing the same value in the dissolve field are merged into a single feature whose geometry is the union of the contributing features. If no dissolve field is specified, all features are merged into one. Optional statistics fields allow computation of sum, mean, minimum, maximum, count, or other aggregations for numeric attributes during the dissolve process.

Cartographers dissolve county polygons on a state name field to create state boundaries from detailed county data. Census analysts dissolve block groups into tracts or tracts into counties to aggregate demographic data to coarser geographic levels. Land managers dissolve individual management unit polygons by ownership type to create consolidated ownership maps. Transportation planners dissolve road segments by route number to create continuous route features. Environmental analysts dissolve land cover patches by class to create simplified vegetation maps.

Dissolve can produce multipart features when the merged geometries are not spatially contiguous (e.g., dissolving non-adjacent parcels with the same owner creates a multipart polygon). The operation may be computationally intensive for large datasets with complex geometries. Attribute information from individual input features is lost unless explicitly summarized through statistical aggregation.