Dissolve Simple is a customized operation used to dissolve
adjacent polygons that have the same value for a specified set
of one or more attributes. As an example, suppose a
Deforestation map with the following atributes shown bellow
and two polygons with their values for illustration only.
They are organized into Scenes and each scene is
subdvided into cells. Cells can be mapped simultaneouly
by different interpreters - cell_oid is distinct
for the green ones and two others beside it - the limit of the
cell_id is the horizontal line.)
a) The dissolved adjacent polygons with the same value of 'class_name' (desmatamento) and 'scene_id' will became just one polygon at the output (union).
Original Polygons
Output
Layer: class_name, scene_id
- b) The dissolved adjacent polygons with the same value of 'class_name' (desmatamento) and 'cell_oid' will became just one polygon at the output (union).
Output Layer : 'class_name', 'cell_oid', 'scene_id'.
Observe that the ligth green ones are not dissolved because the 'cell_oid' is distinct in this case. The set of attributes specified to be used to dissolve polygons are 'class_name' and 'cell_id'. The output attributes are 'class_name', 'cell_oid' and 'scene_id'.
It is accessed through:
Processing > Vector
Processing > Dissolve Simple...
Useful Tips:
Some attributes are default: FID and OGR_GEOMETRY
Be careful when defining output attributes. Selecting certain attributes can prevent polygons from dissolving (in the examples do not select task_id).
Input Attributes Output Attributes