Line of sight (location)

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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

Tap to place the starting point for the line. Tap again to place the end point.

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. Listen for taps on the scene view.
  4. Update the target location with lineOfSight.TargetLocation = scenePoint.

Relevant API

  • AnalysisOverlay
  • LocationLineOfSight
  • SceneView

Tags

3D, line of sight, visibility, visibility analysis

Sample Code

LineOfSightLocation.cs
                                                                                                                                                    
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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.

using Android.App;
using Android.OS;
using Android.Views;
using Android.Widget;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.UI.Controls;
using Esri.ArcGISRuntime.UI.GeoAnalysis;
using System;

namespace ArcGISRuntime.Samples.LineOfSightLocation
{
    [Activity (ConfigurationChanges=Android.Content.PM.ConfigChanges.Orientation | Android.Content.PM.ConfigChanges.ScreenSize)]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Line of sight (location)",
        category: "Analysis",
        description: "Perform a line of sight analysis between two points in real time.",
        instructions: "Tap to place the starting point for the line. Tap again to place the end point.",
        tags: new[] { "3D", "line of sight", "visibility", "visibility analysis" })]
    public class LineOfSightLocation : Activity
    {
        // Hold a reference to the scene view
        private SceneView _mySceneView;

        // URL for an image service to use as an elevation source
        private string _elevationSourceUrl = @"https://elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer";

        // Location line of sight analysis
        private LocationLineOfSight _lineOfSightAnalysis;

        // Observer location for line of sight
        private MapPoint _observerLocation;

        // Target location for line of sight
        private MapPoint _targetLocation;

        // Offset (meters) to use for the observer/target height (z-value for the points)
        private double _zOffset = 2.0;

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            Title = "Line of sight from location";

            // Create the UI
            CreateLayout();

            // Create the Scene, basemap, graphic, and composite symbol
            Initialize();
        }

        private void Initialize()
        {
            // Create a new Scene with an imagery basemap
            Scene myScene = new Scene(BasemapStyle.ArcGISImageryStandard);

            // Create an elevation source for the Scene
            ArcGISTiledElevationSource elevationSrc = new ArcGISTiledElevationSource(new Uri(_elevationSourceUrl));
            myScene.BaseSurface.ElevationSources.Add(elevationSrc);

            // Add the Scene to the SceneView
            _mySceneView.Scene = myScene;

            // Set the viewpoint with a new camera
            Camera newCamera = new Camera(new MapPoint(-121.7, 45.4, SpatialReferences.Wgs84), 10000, 0, 45, 0);
            _mySceneView.SetViewpointCameraAsync(newCamera);

            // Create a new line of sight analysis with arbitrary points (observer and target will be defined by the user)
            _lineOfSightAnalysis = new LocationLineOfSight(new MapPoint(0.0, 0.0, SpatialReferences.Wgs84), new MapPoint(0.0, 0.0, SpatialReferences.Wgs84));

            // Set the visible and obstructed colors (default would be green/red)
            // These are static properties that apply to all line of sight analyses in the scene view
            LineOfSight.VisibleColor = System.Drawing.Color.Cyan;
            LineOfSight.ObstructedColor = System.Drawing.Color.Magenta;

            // Create an analysis overlay to contain the analysis and add it to the scene view
            AnalysisOverlay lineOfSightOverlay = new AnalysisOverlay();
            lineOfSightOverlay.Analyses.Add(_lineOfSightAnalysis);
            _mySceneView.AnalysisOverlays.Add(lineOfSightOverlay);
        }

        private void SceneViewTapped(object sender, GeoViewInputEventArgs e)
        {
            // Ignore if tapped out of bounds (e.g. the sky).
            if (e.Location == null)
            {
                return;
            }

            // When the view is tapped, define the observer or target location with the tap point as appropriate
            if (_observerLocation == null)
            {
                // Define the observer location (plus an offset for observer height) and set the target to the same point
                _observerLocation = new MapPoint(e.Location.X, e.Location.Y, e.Location.Z + _zOffset);
                _lineOfSightAnalysis.ObserverLocation = _observerLocation;
                _lineOfSightAnalysis.TargetLocation = _observerLocation;

                // Clear the target location (if any) so the next click will define the target
                _targetLocation = null;
            }
            else if (_targetLocation == null)
            {
                // Define the target
                _targetLocation = new MapPoint(e.Location.X, e.Location.Y, e.Location.Z + _zOffset);
                _lineOfSightAnalysis.TargetLocation = _targetLocation;

                // Clear the observer location so it can be defined again
                _observerLocation = null;
            }
        }

        private void CreateLayout()
        {
            // Create a new vertical layout for the app
            LinearLayout layout = new LinearLayout(this) { Orientation = Orientation.Vertical };

            // Add the scene view to the layout
            _mySceneView = new SceneView(this);
            layout.AddView(_mySceneView);

            // Wire up tapped event for the scene view
            _mySceneView.GeoViewTapped += SceneViewTapped;

            // Show the layout in the app
            SetContentView(layout);
        }

        protected override void OnDestroy()
        {
            base.OnDestroy();

            // Remove the sceneview
            (_mySceneView.Parent as ViewGroup).RemoveView(_mySceneView);
            _mySceneView.Dispose();
            _mySceneView = null;
        }
    }
}

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