Merging polygons in QGIS involves combining multiple polygons into a single, larger polygon. This can be achieved using several methods, depending on your specific needs:
1. Using the "Merge" Tool
- Open the Processing Toolbox (Ctrl+Shift+T).
- Search for "Merge" and select the "Merge" tool from the Vector geometry tools group.
- Choose the input layer containing the polygons you want to merge.
- Choose an output filename and location.
- Click "Run."
This method merges all polygons in the input layer into a single polygon.
2. Using the "Dissolve" Tool
- Open the Processing Toolbox.
- Search for "Dissolve" and select the "Dissolve" tool from the Vector geometry tools group.
- Choose the input layer containing the polygons you want to merge.
- Optionally, you can specify a field to dissolve by. This will merge only polygons with the same value in that field.
- Choose an output filename and location.
- Click "Run."
The "Dissolve" tool merges polygons based on a specified field, allowing for more control over the merging process.
3. Using the "Union" Tool
- Open the Processing Toolbox.
- Search for "Union" and select the "Union" tool from the Vector overlay tools group.
- Choose the input layer containing the polygons you want to merge.
- Choose another layer as the second input layer. This layer can be the same as the first layer.
- Choose an output filename and location.
- Click "Run."
The "Union" tool merges polygons from two layers, creating a new layer with the combined polygons.
Practical Insights
- Ensure the polygons you want to merge are in the same coordinate system.
- Use the "Dissolve" tool for merging polygons with shared attributes.
- Use the "Union" tool for merging polygons from different layers.
These methods allow you to effectively merge polygons in QGIS, simplifying your data and creating new shapes for analysis and visualization.
