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 System;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.UI.Controls;
using Esri.ArcGISRuntime.UI.GeoAnalysis;
using Foundation;
using UIKit;

namespace ArcGISRuntime.Samples.LineOfSightLocation
{
    [Register("LineOfSightLocation")]
    [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 : UIViewController
    {
        // Hold references to UI controls.
        private SceneView _mySceneView;

        // URL for an image service to use as an elevation source.
        private const 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 const double ZOffset = 2.0;

        public LineOfSightLocation()
        {
            Title = "Line of sight (location)";
        }

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

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

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

            // 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;
            }
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();
            Initialize();
        }

        public override void LoadView()
        {
            // Create the views.
            _mySceneView = new SceneView();
            _mySceneView.TranslatesAutoresizingMaskIntoConstraints = false;

            View = new UIView {BackgroundColor = ApplicationTheme.BackgroundColor};

            // Add the views.
            View.AddSubviews(_mySceneView);

            // Lay out the views.
            NSLayoutConstraint.ActivateConstraints(new[]
            {
                _mySceneView.TopAnchor.ConstraintEqualTo(View.SafeAreaLayoutGuide.TopAnchor),
                _mySceneView.BottomAnchor.ConstraintEqualTo(View.BottomAnchor),
                _mySceneView.LeadingAnchor.ConstraintEqualTo(View.LeadingAnchor),
                _mySceneView.TrailingAnchor.ConstraintEqualTo(View.TrailingAnchor)
            });
        }

        public override void ViewWillAppear(bool animated)
        {
            base.ViewWillAppear(animated);

            // Subscribe to events.
            _mySceneView.GeoViewTapped += SceneViewTapped;
        }

        public override void ViewDidDisappear(bool animated)
        {
            base.ViewDidDisappear(animated);

            // Unsubscribe from events, per best practice.
            _mySceneView.GeoViewTapped -= SceneViewTapped;
        }
    }
}

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