30 lines
1.2 KiB
Markdown
30 lines
1.2 KiB
Markdown
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### Aereal Weighting
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Aereal weighting is a simple interpolation technique to assign a value
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to a polygon given a set of polygons with one value assigned to each one.
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The value is assigned by averaging the values of intersecting areas
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weighted by the intersection area.
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Its accuracy depends on the values assigned to reference areas being
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homogeneous over each area.
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The `cdb_overlap_function` takes three required parameters:
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* `geometry` a Polygon geometry which defines the area where a value will be
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estimated.
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* `table_name`: name of the values table that provides the source values;
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this table must have a geometric column `the_geom` containing the polygons
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to which values are assigned.
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* `column_name`: name of the column that contains the values in the values
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table (should be a numeric column)
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There's also an additional optional parameter to define the schema to which
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the values table belongs. This is necessary only if it is not in the
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`search_path`. Note that `table_name` should never include the schema in it.
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* `schema_name` name of the schema that contains the values table
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This function returns a numeric value resulting from the aggregation
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of the polygons in
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