Returns a feature containing the union of the geometries of two features.
Feature.union(right, maxError, proj)
|Element||The feature containing the geometry used as the left operand of the operation. The properties of the result will be copied from this object.|
|Element||The feature containing the geometry used as the right operand of the operation. The properties of this object are ignored.|
|ErrorMargin, default: null||The maximum amount of error tolerated when performing any necessary reprojection.|
|Projection, default: null||The projection in which to perform the operation. If not specified, the operation will be performed in a spherical coordinate system, and linear distances will be in meters on the sphere.|