Line of sight location

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Sample viewer app

Perform a line of sight analysis between two points in real time.

Image of line of sight location

Use case

A line of sight analysis can be used to assess whether a view is obstructed between an observer and a target. Obstructing features could either be natural, like topography, or man-made, like buildings. Consider an events planning company wanting to commemorate a national event by lighting sequential beacons across hill summits or roof tops. To guarantee a successful event, ensuring an unobstructed line of sight between neighboring beacons would allow each beacon to be activated as intended.

How to use the sample

The sample loads with a preset observer and target location, linked by a colored line. A red segment on the line means the view between observer and target is obstructed, whereas green means the view is unobstructed.

Click to turn on the mouse move event listener, then move the mouse to update the target location in real time. Click again to lock the target location.

How it works

  1. Create an AnalysisOverlay and add it to the scene view.
  2. Create a LocationLineOfSight with initial observer and target locations and add it to the analysis overlay.
  3. Make an EventHandler<MouseEvent> to capture mouse movement. Turn the screen point into a scene point with sceneView.screenToLocationAsync(screenPoint).
  4. Update the target location with lineOfSight.setTargetLocation(scenePoint).

Relevant API

  • AnalysisOverlay
  • LocationLineOfSight
  • SceneView

Tags

3D, line of sight, visibility, visibility analysis

Sample Code

LineOfSightLocationSample.java
                                                                                                                                                    
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/*
 * Copyright 2017 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.line_of_sight_location;

import java.util.concurrent.ExecutionException;

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.geometry.Point2D;
import javafx.scene.Scene;
import javafx.scene.input.MouseButton;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

import com.esri.arcgisruntime.concurrent.ListenableFuture;
import com.esri.arcgisruntime.geoanalysis.LocationLineOfSight;
import com.esri.arcgisruntime.geometry.Point;
import com.esri.arcgisruntime.geometry.SpatialReferences;
import com.esri.arcgisruntime.mapping.ArcGISScene;
import com.esri.arcgisruntime.mapping.ArcGISTiledElevationSource;
import com.esri.arcgisruntime.mapping.Basemap;
import com.esri.arcgisruntime.mapping.Surface;
import com.esri.arcgisruntime.mapping.view.AnalysisOverlay;
import com.esri.arcgisruntime.mapping.view.Camera;
import com.esri.arcgisruntime.mapping.view.SceneView;

public class LineOfSightLocationSample extends Application {

  private SceneView sceneView;

  @Override
  public void start(Stage stage) {

    try {

      // create stack pane and JavaFX app scene
      StackPane stackPane = new StackPane();
      Scene fxScene = new Scene(stackPane);

      // set title, size, and add JavaFX scene to stage
      stage.setTitle("Line of Sight Location Sample");
      stage.setWidth(800);
      stage.setHeight(700);
      stage.setScene(fxScene);
      stage.show();

      // create a scene and add a basemap to it
      ArcGISScene scene = new ArcGISScene();
      scene.setBasemap(Basemap.createTopographic());

      // add the SceneView to the stack pane
      sceneView = new SceneView();
      sceneView.setArcGISScene(scene);
      stackPane.getChildren().add(sceneView);

      // add base surface for elevation data
      Surface surface = new Surface();
      surface.getElevationSources().add(new ArcGISTiledElevationSource("https://elevation3d.arcgis" +
          ".com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer"));
      scene.setBaseSurface(surface);

      // create an analysis overlay for the line of sight
      AnalysisOverlay analysisOverlay = new AnalysisOverlay();
      sceneView.getAnalysisOverlays().add(analysisOverlay);

      // initialize a line of sight analysis and add it to the analysis overlay
      Point observerLocation = new Point(-73.06958032962375, -49.253112971555446, 2000, SpatialReferences.getWgs84());
      Point targetLocation = new Point(-73.079266999709162, -49.300457676730559, 1312, SpatialReferences.getWgs84());
      LocationLineOfSight lineOfSight = new LocationLineOfSight(observerLocation, targetLocation);
      analysisOverlay.getAnalyses().add(lineOfSight);

      // initialize the viewpoint
      Camera camera = new Camera(new Point(-73.0815, -49.3272, 4059, SpatialReferences.getWgs84()), 11, 62, 0);
      sceneView.setViewpointCamera(camera);

      // remove default mouse move handler
      sceneView.setOnMouseMoved(null);

      // update the target location when the mouse moves
      EventHandler<MouseEvent> mouseMoveEventHandler = event -> {
        Point2D point2D = new Point2D(event.getX(), event.getY());
        // get the scene location from the screen position
        ListenableFuture<Point> pointFuture = sceneView.screenToLocationAsync(point2D);
        pointFuture.addDoneListener(() -> {
          try {
            Point point = pointFuture.get();
            // update the target location
            lineOfSight.setTargetLocation(point);
          } catch (InterruptedException | ExecutionException e) {
            e.printStackTrace();
          }
        });
      };

      // mouse click to start/stop moving target location
      sceneView.setOnMouseClicked(event -> {
        if (event.isStillSincePress() && event.getButton() == MouseButton.PRIMARY) {
          if (sceneView.getOnMouseMoved() == null) {
            sceneView.setOnMouseMoved(mouseMoveEventHandler);
          } else {
            sceneView.setOnMouseMoved(null);
          }
        }
      });

    } 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 (sceneView != null) {
      sceneView.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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