Perform spatial operations

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

Image of perform spatial operations

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

Select a spatial operation from the overflow menu. When an operation is selected, the resulting geometry is shown in red.

How it works

  1. Create two GraphicsOverlays, one to show polygons and another to show the relationships between them.
  2. Define a PointCollection of each Geometry.
  3. Add the overlapping polygons to a 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. Add the resultant geometry to a new Graphic and display it by adding it to the second GraphicsOverlay.

Relevant API

  • Geometry
  • GeometryEngine
  • GeometryEngine.difference
  • GeometryEngine.intersection
  • GeometryEngine.symmetricDifference
  • GeometryEngine.union
  • Graphic
  • GraphicsOverlay

Tags

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

Sample Code

MainActivity.java
                                                                                                                                                                                                                  
/*
 * Copyright 2016 Esri
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.esri.arcgisruntime.sample.performspatialoperations;

import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

import androidx.appcompat.app.AppCompatActivity;
import com.esri.arcgisruntime.ArcGISRuntimeEnvironment;
import com.esri.arcgisruntime.geometry.Geometry;
import com.esri.arcgisruntime.geometry.GeometryEngine;
import com.esri.arcgisruntime.geometry.Part;
import com.esri.arcgisruntime.geometry.PartCollection;
import com.esri.arcgisruntime.geometry.Point;
import com.esri.arcgisruntime.geometry.PointCollection;
import com.esri.arcgisruntime.geometry.Polygon;
import com.esri.arcgisruntime.geometry.SpatialReferences;
import com.esri.arcgisruntime.mapping.ArcGISMap;
import com.esri.arcgisruntime.mapping.BasemapStyle;
import com.esri.arcgisruntime.mapping.view.Graphic;
import com.esri.arcgisruntime.mapping.view.GraphicsOverlay;
import com.esri.arcgisruntime.mapping.view.MapView;
import com.esri.arcgisruntime.symbology.SimpleFillSymbol;
import com.esri.arcgisruntime.symbology.SimpleLineSymbol;

public class MainActivity extends AppCompatActivity {

  final private GraphicsOverlay inputGeometryOverlay = new GraphicsOverlay();
  final private GraphicsOverlay resultGeometryOverlay = new GraphicsOverlay();
  // simple black (0xFF000000) line symbol for outlines
  final private SimpleLineSymbol lineSymbol = new SimpleLineSymbol(SimpleLineSymbol.Style.SOLID, 0xFF000000, 1);
  final private SimpleFillSymbol resultFillSymbol = new SimpleFillSymbol(SimpleFillSymbol.Style.SOLID, 0xFFE91F1F,
      lineSymbol);
  private Polygon inputPolygon1;
  private Polygon inputPolygon2;
  // The spatial operation switching menu items.
  private MenuItem noOperationMenuItem = null;
  private MenuItem intersectionMenuItem = null;
  private MenuItem unionMenuItem = null;
  private MenuItem differenceMenuItem = null;
  private MenuItem symmetricDifferenceMenuItem = null;
  private MapView mMapView;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // authentication with an API key or named user is required to access basemaps and other
    // location services
    ArcGISRuntimeEnvironment.setApiKey(BuildConfig.API_KEY);

    mMapView = findViewById(R.id.mapView);

    // create ArcGISMap with topographic basemap
    ArcGISMap map = new ArcGISMap(BasemapStyle.ARCGIS_LIGHT_GRAY);
    mMapView.setMap(map);

    // create graphics overlays to show the inputs and results of the spatial operation
    mMapView.getGraphicsOverlays().add(inputGeometryOverlay);
    mMapView.getGraphicsOverlays().add(resultGeometryOverlay);

    // create input polygons and add graphics to display these polygons in an overlay
    createPolygons();

    // center the map view on the input geometries
    Geometry viewpointGeom = GeometryEngine.union(inputPolygon1, inputPolygon2).getExtent();
    mMapView.setViewpointGeometryAsync(viewpointGeom, 20);
  }

  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);

    // Get the menu items that perform spatial operations.
    noOperationMenuItem = menu.getItem(0);
    intersectionMenuItem = menu.getItem(1);
    unionMenuItem = menu.getItem(2);
    differenceMenuItem = menu.getItem(3);
    symmetricDifferenceMenuItem = menu.getItem(4);

    // set the 'no-op' menu item checked by default
    noOperationMenuItem.setChecked(true);

    return true;
  }

  @Override
  public boolean onOptionsItemSelected(MenuItem item) {
    // handle menu item selection
    int itemId = item.getItemId();

    // clear previous operation result
    resultGeometryOverlay.getGraphics().clear();

    // perform spatial operations and add results as graphics, depending on the option selected
    // if-else is used because this sample is used elsewhere as a Library module
    if (itemId == R.id.action_no_operation) {
      // no spatial operation - graphics have been cleared previously
      noOperationMenuItem.setChecked(true);
      return true;
    } else if (itemId == R.id.action_intersection) {
      intersectionMenuItem.setChecked(true);
      showGeometry(GeometryEngine.intersection(inputPolygon1, inputPolygon2));
      return true;
    } else if (itemId == R.id.action_union) {
      unionMenuItem.setChecked(true);
      showGeometry(GeometryEngine.union(inputPolygon1, inputPolygon2));
      return true;
    } else if (itemId == R.id.action_difference) {
      differenceMenuItem.setChecked(true);
      // note that the difference method gives different results depending on the order of input geometries
      showGeometry(GeometryEngine.difference(inputPolygon1, inputPolygon2));
      return true;
    } else if (itemId == R.id.action_symmetric_difference) {
      symmetricDifferenceMenuItem.setChecked(true);
      showGeometry(GeometryEngine.symmetricDifference(inputPolygon1, inputPolygon2));
      return true;
    } else {
      return super.onOptionsItemSelected(item);
    }
  }

  private void showGeometry(Geometry resultGeometry) {
    // add a graphic from the result geometry, showing result in red (0xFFE91F1F)
    Graphic resultGraphic = new Graphic(resultGeometry, resultFillSymbol);
    resultGeometryOverlay.getGraphics().add(resultGraphic);

    // select the result to highlight it
    resultGraphic.setSelected(true);
  }

  private void createPolygons() {

    // create input polygon 1
    PointCollection pointsPoly = new PointCollection(SpatialReferences.getWebMercator());
    pointsPoly.add(new Point(-13160, 6710100));
    pointsPoly.add(new Point(-13300, 6710500));
    pointsPoly.add(new Point(-13760, 6710730));
    pointsPoly.add(new Point(-14660, 6710000));
    pointsPoly.add(new Point(-13960, 6709400));
    inputPolygon1 = new Polygon(pointsPoly);

    // create and add a blue graphic to show input polygon 1
    SimpleFillSymbol fillSymbol = new SimpleFillSymbol(SimpleFillSymbol.Style.SOLID, 0x990000CC, lineSymbol);
    inputGeometryOverlay.getGraphics().add(new Graphic(inputPolygon1, fillSymbol));

    // create input polygon 2 with a green (0xFF009900) symbol
    // outer ring
    PointCollection outerRingSegmentCollection = new PointCollection(SpatialReferences.getWebMercator());
    outerRingSegmentCollection.add(new Point(-13060, 6711030));
    outerRingSegmentCollection.add(new Point(-12160, 6710730));
    outerRingSegmentCollection.add(new Point(-13160, 6709700));
    outerRingSegmentCollection.add(new Point(-14560, 6710730));
    outerRingSegmentCollection.add(new Point(-13060, 6711030));
    Part outerRing = new Part(outerRingSegmentCollection);

    // inner ring
    PointCollection innerRingSegmentCollection = new PointCollection(SpatialReferences.getWebMercator());
    innerRingSegmentCollection.add(new Point(-13060, 6710910));
    innerRingSegmentCollection.add(new Point(-12450, 6710660));
    innerRingSegmentCollection.add(new Point(-13160, 6709900));
    innerRingSegmentCollection.add(new Point(-14160, 6710630));
    innerRingSegmentCollection.add(new Point(-13060, 6710910));
    Part innerRing = new Part(innerRingSegmentCollection);

    // add both parts (rings) to a part collection and create a geometry from it
    PartCollection polygonParts = new PartCollection(outerRing);
    polygonParts.add(innerRing);
    inputPolygon2 = new Polygon(polygonParts);

    // create and add a green graphic to show input polygon 2
    fillSymbol = new SimpleFillSymbol(SimpleFillSymbol.Style.SOLID, 0x99009900, lineSymbol);
    inputGeometryOverlay.getGraphics().add(new Graphic(inputPolygon2, fillSymbol));
  }

  @Override
  protected void onPause() {
    mMapView.pause();
    super.onPause();
  }

  @Override
  protected void onResume() {
    super.onResume();
    mMapView.resume();
  }

  @Override
  protected void onDestroy() {
    super.onDestroy();
    mMapView.dispose();
  }
}