Function Description
Polygon aggregation fuses polygon features within a specified distance into new polygon features, resulting in an aggregated polygon dataset.
Application Scenarios
A common application scenario is when needing to determine the clustering degree of rural settlements. Indicators such as contiguity are typically used for judgment. Contiguity refers to aggregating plots or buildings within a certain range into a single patch. For example, with an aggregation distance of 100 meters for construction land plots, a 100-meter buffer is created for each plot to be aggregated, and all plots within the range are merged.
Different aggregation bound distances produce different effects, as shown in the following figure:
If you want to exclude some independent and fragmented polygons from the data, you can set the limited area in the parameters, as shown in the following figure:
Sometimes, gaps (holes) may appear in the result. At this time, you can set the "holes define an area" parameter to eliminate them, as shown in the following figure:
Functional Entry
- Data Tab -> Data Processing -> Vector -> Polygon Aggregation.
- Toolbox -> Data Processing -> Vector -> Polygon Aggregation.
Parameter description
- Source Dataset: Sets the dataset to be processed and its data source. The dataset must be a polygon dataset.
- Aggregation bound distance: Sets the distance that must be satisfied between the boundaries of polygon features during aggregation, meaning aggregation only occurs where the boundaries of two polygon features are within the specified aggregation distance. The value range is greater than 0.
- Unit: Sets the unit for the aggregation bound distance. The default is meters for planar and projected coordinate systems, and degrees for geographic coordinate systems.
- Limited area: Sets the minimum area for independent fragmented polygons in the aggregation result; polygons smaller than this area will be eliminated. The unit of area is consistent with the unit of the aggregation bound distance. For example, if the unit above is selected as meters, the unit of area here is square meters. The default value is 0, meaning all polygons are retained.
- Holes define an area: Sets the minimum area for holes inside the aggregated result polygons; holes smaller than this area will be filled. The unit of area is consistent with the unit of the aggregation bound distance. For example, if the unit above is selected as meters, the unit of area here is square meters. The default value is 0, meaning all holes within polygon features are retained.
- Aggregation Field: Features with the same aggregation field value will be aggregated. For example, when aggregating building polygons, nearby water body polygons should not be aggregated in principle. Supported field value types are: Boolean, Integer, Long, Date, Timestamp.
- Result Data: Sets the result datasource and dataset name.
Related Topics