Geodesic operations

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Sample viewer app

Calculate a geodesic path between two points and measure its distance.

Image of geodesic operations

Use case

A geodesic distance provides an accurate, real-world distance between two points. Visualizing flight paths between cities is a common example of a geodesic operation since the flight path between two airports takes into account the curvature of the earth, rather than following the planar path between those points, which appears as a straight line on a projected map.

How to use the sample

Click anywhere on the map. A line graphic will display the geodesic line between the two points. In addition, text that indicates the geodesic distance between the two points will be updated. Click elsewhere and a new line will be created.

How it works

  1. Create a Point in and display it as a Graphic.
  2. Obtain a new point when a click occurs on the MapView and add this point as a graphic.
  3. Create a Polyline from the two points.
  4. Execute GeometryEngine.densifyGeodetic() by passing in the created polyine then create a graphic from the returned Geometry.
  5. Execute GeometryEngine.lengthGeodetic() by passing in the two points and display the returned length on the screen.

Relevant API

  • GeometryEngine

About the data

The Imagery basemap style provides the global context for the displayed geodesic line.

Tags

densify, distance, geodesic, geodetic

Sample Code

GeodesicOperationsSample.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.geodesic_operations;

import java.text.DecimalFormat;
import java.util.Arrays;

import javafx.application.Application;
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.*;
import javafx.scene.paint.Paint;
import javafx.stage.Stage;

import com.esri.arcgisruntime.ArcGISRuntimeEnvironment;
import com.esri.arcgisruntime.geometry.GeodeticCurveType;
import com.esri.arcgisruntime.geometry.Geometry;
import com.esri.arcgisruntime.geometry.GeometryEngine;
import com.esri.arcgisruntime.geometry.LinearUnit;
import com.esri.arcgisruntime.geometry.LinearUnitId;
import com.esri.arcgisruntime.geometry.Point;
import com.esri.arcgisruntime.geometry.PointCollection;
import com.esri.arcgisruntime.geometry.Polyline;
import com.esri.arcgisruntime.geometry.SpatialReference;
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.SimpleLineSymbol;
import com.esri.arcgisruntime.symbology.SimpleMarkerSymbol;

public class GeodesicOperationsSample extends Application {

  private MapView mapView;
  private final SpatialReference srWgs84 = SpatialReferences.getWgs84();

  @Override
  public void start(Stage stage) {

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

      // set title, size, and add scene to stage
      stage.setTitle("Geodesic Operations Sample");
      stage.setWidth(800);
      stage.setHeight(700);
      stage.setScene(fxScene);
      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 standard imagery basemap style
      ArcGISMap map = new ArcGISMap(BasemapStyle.ARCGIS_IMAGERY_STANDARD);

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

      // create a graphics overlay
      GraphicsOverlay graphicsOverlay = new GraphicsOverlay();
      mapView.getGraphicsOverlays().add(graphicsOverlay);

      // add a graphic at JFK airport to represent the flight start location
      Point start = new Point(-73.7781, 40.6413, srWgs84);
      SimpleMarkerSymbol locationMarker = new SimpleMarkerSymbol(SimpleMarkerSymbol.Style.CIRCLE, 0xFF0000FF, 10);
      Graphic startLocation = new Graphic(start, locationMarker);
      graphicsOverlay.getGraphics().add(startLocation);

      // create a graphic for the destination
      Graphic endLocation = new Graphic();
      endLocation.setSymbol(locationMarker);
      graphicsOverlay.getGraphics().add(endLocation);

      // create a graphic representing the geodesic path between the two locations
      Graphic path = new Graphic();
      path.setSymbol(new SimpleLineSymbol(SimpleLineSymbol.Style.DASH, 0xFF0000FF, 5));
      graphicsOverlay.getGraphics().add(path);

      // create a label to show the distance
      Label distanceLabel = new Label();
      DecimalFormat formatter = new DecimalFormat("#0.00 km");
      distanceLabel.setText(formatter.format(0.0));
      VBox labelBox = new VBox(distanceLabel);
      labelBox.setBackground(new Background(new BackgroundFill(Paint.valueOf("rgba(0,0,0,0.3)"), CornerRadii.EMPTY,
              Insets.EMPTY)));
      labelBox.setAlignment(Pos.CENTER);
      labelBox.setPadding(new Insets(5));
      labelBox.setMaxSize(80, 20);
      labelBox.getStyleClass().add("panel-region");

      // create a linear unit for measuring the distance
      LinearUnit unitOfMeasurement = new LinearUnit(LinearUnitId.KILOMETERS);

      // and a mouse click listener to get the user's input for the destination
      mapView.setOnMouseClicked(e -> {
        if (e.isStillSincePress() && e.getButton() == MouseButton.PRIMARY) {
          // change the end location's geometry to the clicked location
          Point2D point2D = new Point2D(e.getX(), e.getY());
          Point destination = (Point) GeometryEngine.project(mapView.screenToLocation(point2D), srWgs84);
          endLocation.setGeometry(destination);
          // create a straight line path between the start and end locations
          PointCollection points = new PointCollection(Arrays.asList(start, destination), srWgs84);
          Polyline polyline = new Polyline(points);
          // densify the path as a geodesic curve and show it with the path graphic
          Geometry pathGeometry = GeometryEngine.densifyGeodetic(polyline, 1, unitOfMeasurement, GeodeticCurveType
              .GEODESIC);
          path.setGeometry(pathGeometry);
          // calculate the path distance
          double distance = GeometryEngine.lengthGeodetic(pathGeometry, unitOfMeasurement, GeodeticCurveType.GEODESIC);
          distanceLabel.setText(formatter.format(distance));
        }
      });

      // add the scene view and label box to the stack pane
      stackPane.getChildren().addAll(mapView, labelBox);
      StackPane.setMargin(labelBox, new Insets(10, 0, 0, 10));
      StackPane.setAlignment(labelBox, Pos.TOP_LEFT);
    } 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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