Nearest vertex

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Find the closest vertex and coordinate of a geometry to a point.

Image of nearest vertex

Use case

Determine the shortest distance between a location and the boundary of an area. For example, developers can snap imprecise user clicks to a geometry if the click is within a certain distance of the geometry.

How to use the sample

Click anywhere on the map. An orange cross will show at that location. A blue circle will show the polygon's nearest vertex to the point that was clicked. A red diamond will appear at the coordinate on the geometry that is nearest to the point that was clicked. If clicked inside the geometry, the red and orange markers will overlap. The information box showing distance between the clicked point and the nearest vertex/coordinate will be updated with every new location clicked.

How it works

  1. Get a Geometry and a Point to check the nearest vertex against.
  2. Call GeometryEngine.nearestVertex(inputGeometry, point).
  3. Use the returned ProximityResult to get the Point representing the polygon vertex, and to determine the distance between that vertex and the clicked point.
  4. Call GeometryEngine.nearestCoordinate(inputGeometry, point).
  5. Use the returned ProximityResult to get the Point representing the coordinate on the polygon, and to determine the distance between that coordinate and the clicked point.

Relevant API

  • GeometryEngine
  • ProximityResult

Tags

analysis, coordinate, geometry, nearest, proximity, vertex

Sample Code

NearestVertexSample.java
                                                                                                                                                                                               
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/*
 * Copyright 2018 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.samples.nearest_vertex;

import java.util.Arrays;

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.geometry.Insets;
import javafx.geometry.Point2D;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.input.MouseButton;
import javafx.scene.layout.Background;
import javafx.scene.layout.BackgroundFill;
import javafx.scene.layout.CornerRadii;
import javafx.scene.layout.StackPane;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Paint;
import javafx.stage.Stage;

import com.esri.arcgisruntime.ArcGISRuntimeEnvironment;
import com.esri.arcgisruntime.geometry.GeometryEngine;
import com.esri.arcgisruntime.geometry.Point;
import com.esri.arcgisruntime.geometry.PointCollection;
import com.esri.arcgisruntime.geometry.Polygon;
import com.esri.arcgisruntime.geometry.ProximityResult;
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;
import com.esri.arcgisruntime.symbology.SimpleMarkerSymbol;

public class NearestVertexSample extends Application {

  private MapView mapView;

  @Override
  public void start(Stage stage) {

    try {
      // create stack pane and application scene
      StackPane stackPane = new StackPane();
      Scene scene = new Scene(stackPane);
      scene.getStylesheets().add(getClass().getResource("/nearest_vertex/style.css").toExternalForm());

      // set title, size, and add scene to stage
      stage.setTitle("Nearest Vertex Sample");
      stage.setWidth(800);
      stage.setHeight(700);
      stage.setScene(scene);
      stage.show();

      // authentication with an API key or named user is required to access basemaps and other location services
      String yourAPIKey = System.getProperty("apiKey");
      ArcGISRuntimeEnvironment.setApiKey(yourAPIKey);

      // create a map with the topographic basemap style
      ArcGISMap map = new ArcGISMap(BasemapStyle.ARCGIS_TOPOGRAPHIC);

      // create a map view and set the map to it
      mapView = new MapView();
      mapView.setMap(map);

      // create a graphics overlay to show the polygon, clicked location, and nearest vertex/coordinate
      GraphicsOverlay graphicsOverlay = new GraphicsOverlay();
      mapView.getGraphicsOverlays().add(graphicsOverlay);

      // create a graphic for the polygon
      PointCollection polygonPoints = new PointCollection(SpatialReferences.getWebMercator());
      polygonPoints.addAll(Arrays.asList(
          new Point(-5991501.677830, 5599295.131468),
          new Point(-6928550.398185, 2087936.739807),
          new Point(-3149463.800709, 1840803.011362),
          new Point(-1563689.043184, 3714900.452072),
          new Point(-3180355.516764, 5619889.608838)));
      Polygon polygon = new Polygon(polygonPoints);
      SimpleLineSymbol polygonOutlineSymbol = new SimpleLineSymbol(SimpleLineSymbol.Style.SOLID, 0xFF00FF00, 2);
      SimpleFillSymbol polygonFillSymbol = new SimpleFillSymbol(SimpleFillSymbol.Style.FORWARD_DIAGONAL, 0xFF00FF00, polygonOutlineSymbol);
      Graphic polygonGraphic = new Graphic(polygon, polygonFillSymbol);
      graphicsOverlay.getGraphics().add(polygonGraphic);

      // create graphics for the clicked location, nearest coordinate, and nearest vertex markers
      SimpleMarkerSymbol clickedLocationSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbol.Style.X, 0xFFFFA500, 15);
      SimpleMarkerSymbol nearestCoordinateSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbol.Style.DIAMOND, 0xFFFF0000, 10);
      SimpleMarkerSymbol nearestVertexSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbol.Style.CIRCLE, 0xFF0000FF, 15);
      Graphic clickedLocationGraphic = new Graphic();
      clickedLocationGraphic.setSymbol(clickedLocationSymbol);
      Graphic nearestCoordinateGraphic = new Graphic();
      nearestCoordinateGraphic.setSymbol(nearestCoordinateSymbol);
      Graphic nearestVertexGraphic = new Graphic();
      nearestVertexGraphic.setSymbol(nearestVertexSymbol);
      graphicsOverlay.getGraphics().addAll(Arrays.asList(clickedLocationGraphic, nearestCoordinateGraphic, nearestVertexGraphic));

      // create a label to show the distances between the nearest vertex and nearest coordinate to the clicked location
      Label distancesLabel = new Label("");
      distancesLabel.getStyleClass().add("panel-label");

      // create a black background for the label
      VBox controlsVBox = new VBox(6);
      controlsVBox.setBackground(new Background(new BackgroundFill(Paint.valueOf("rgba(0,0,0,0.3)"), CornerRadii.EMPTY,
          Insets.EMPTY)));
      controlsVBox.setPadding(new Insets(10.0));
      controlsVBox.setMaxSize(300, 50);
      controlsVBox.getStyleClass().add("panel-region");
      controlsVBox.getChildren().add(distancesLabel);
      // hide it until the label text is set
      controlsVBox.visibleProperty().bind(Bindings.createBooleanBinding(() -> !distancesLabel.getText().equals(""), distancesLabel.textProperty()));
      controlsVBox.managedProperty().bind(controlsVBox.visibleProperty());

      // get the nearest vertex and coordinate where the user clicks
      mapView.setOnMouseClicked(e -> {
        if (e.isStillSincePress() && e.getButton() == MouseButton.PRIMARY) {
          // create a point from where the user clicked
          Point2D point = new Point2D(e.getX(), e.getY());

          // create a map point from a point
          Point mapPoint = mapView.screenToLocation(point);

          // the map point should be normalized to the central meridian when wrapping around a map, so its value stays within the coordinate system of the map view
          Point normalizedMapPoint = (Point) GeometryEngine.normalizeCentralMeridian(mapPoint);
          // show where the user clicked
          clickedLocationGraphic.setGeometry(normalizedMapPoint);

          // show the nearest coordinate and vertex
          ProximityResult nearestCoordinateResult = GeometryEngine.nearestCoordinate(polygon, normalizedMapPoint);
          ProximityResult nearestVertexResult = GeometryEngine.nearestVertex(polygon, normalizedMapPoint);
          nearestVertexGraphic.setGeometry(nearestVertexResult.getCoordinate());
          nearestCoordinateGraphic.setGeometry(nearestCoordinateResult.getCoordinate());

          // show the distances to the nearest vertex and nearest coordinate rounded to the nearest kilometer
          int vertexDistance = (int) (nearestVertexResult.getDistance() / 1000.0);
          int coordinateDistance = (int) (nearestCoordinateResult.getDistance() / 1000.0);
          distancesLabel.setText("Vertex distance: " + vertexDistance + " km\nCoordinate distance: " + coordinateDistance + " km");
        }
      });

      // zoom to the polygon's extent
      mapView.setViewpointGeometryAsync(polygon.getExtent(), 100);

      // add the map view and label to the stack pane
      stackPane.getChildren().addAll(mapView, controlsVBox);
      StackPane.setAlignment(controlsVBox, Pos.TOP_LEFT);
      StackPane.setMargin(controlsVBox, new Insets(10, 0, 0, 10));
    } catch (Exception e) {
      // on any error, display the stack trace.
      e.printStackTrace();
    }
  }

  /**
   * Stops and releases all resources used in application.
   */
  @Override
  public void stop() {

    if (mapView != null) {
      mapView.dispose();
    }
  }

  /**
   * Opens and runs application.
   *
   * @param args arguments passed to this application
   */
  public static void main(String[] args) {

    Application.launch(args);
  }

}

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