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Perform spatial operations

Find the union, intersection, or difference of two geometries.

screenshot

Use case

The different spatial operations (union, difference, symmetric difference, and intersection) can be used for a variety of spatial analyses. For example, government authorities may use the intersect operation to determine whether a proposed road cuts through a restricted piece of land such as a nature reserve or a private property. When these operations are chained together, they become even more powerful. An analysis of food deserts within an urban area might begin by union-ing service areas of grocery stores, farmer's markets, and food co-ops. Taking the difference between this single geometry of all services areas and that of a polygon delineating a neighborhood would reveal the areas within that neighborhood where access to healthy, whole foods may not exist.

How to use the sample

The sample provides an option to select a spatial operation. When an operation is selected, the resulting geometry is shown in red. The 'reset operation' button undoes the action and allow selecting a different operation.

How it works

  1. Create a GraphicsOverlay and add it to the MapView.
  2. Define a PointCollection of each Geometry.
  3. Add the overlapping polygons to the graphics overlay.
  4. Perform spatial relationships between the polygons by using the appropriate operation:
    • GeometryEngine.Union(geometry1, geometry2) - This method returns the two geometries united together as one geometry.
    • GeometryEngine.Difference(geometry1, geometry2) - This method returns any part of Geometry2 that does not intersect Geometry1.
    • GeometryEngine.SymmetricDifference(geometry1, geometry2) - This method returns any part of Geometry1 or Geometry2 which do not intersect.
    • GeometryEngine.Intersection(geometry1, geometry2) - This method returns the intersection of Geometry1 and Geometry2.
  5. Use the geometry that is returned from the method call to create a new Graphic and add it to the graphics overlay for it to be displayed.

Relevant API

  • Geometry
  • GeometryEngine
  • GeometryEngine.Difference
  • GeometryEngine.Intersection
  • GeometryEngine.SymmetricDifference
  • GeometryEngine.Union
  • Graphic
  • GraphicsOverlay

Tags

analysis, combine, difference, geometry, intersection, merge, polygon, union