Viewshed (location)

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Perform a viewshed analysis from a defined vantage point.

Image of viewshed location

Use case

A 3D viewshed analysis is a type of visual analysis you can perform on a scene. The viewshed shows what can be seen from a given location. The output is an overlay with two different colors - one representing the visible areas (green) and the other representing the obstructed areas (red). Viewshed analysis is a form of "exploratory analysis", which means the results are calculated on the current scale of the data, and the results are generated very quickly. If more "conclusive" results are required, consider using a GeoprocessingTask to perform a viewshed instead.

How to use the sample

Use the sliders to change the properties (heading, pitch, etc.), of the viewshed and see them updated in real time.

How it works

  1. Create a LocationViewshed passing in the observer location, heading, pitch, horizontal/vertical angles, and min/max distances.
  2. Set the property values on the viewshed instance for location, direction, range, and visibility properties.

Relevant API

  • AnalysisOverlay
  • ArcGISSceneLayer
  • ArcGISTiledElevationSource
  • LocationViewshed
  • Viewshed

About the data

The scene shows a buildings layer in Brest, France hosted on ArcGIS Online.

Tags

3D, frustum, scene, viewshed, visibility analysis

Sample Code

ViewshedLocation.cs
                                                                                                                                                                                                                                                                         
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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: https://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.Symbology;
using Esri.ArcGISRuntime.UI;
using Esri.ArcGISRuntime.UI.Controls;
using Esri.ArcGISRuntime.UI.GeoAnalysis;
using System;
using Surface = Esri.ArcGISRuntime.Mapping.Surface;

namespace ArcGISRuntime.Samples.ViewshedLocation
{
    [Activity (ConfigurationChanges=Android.Content.PM.ConfigChanges.Orientation | Android.Content.PM.ConfigChanges.ScreenSize)]
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Viewshed (location)",
        category: "Analysis",
        description: "Perform a viewshed analysis from a defined vantage point.",
        instructions: "Use the sliders to change the properties (heading, pitch, etc.), of the viewshed and see them updated in real time.",
        tags: new[] { "3D", "frustum", "scene", "viewshed", "visibility analysis" })]
    public class ViewshedLocation : Activity
    {
        // Hold a reference to the scene view.
        private SceneView _mySceneView;

        // Hold the URL to the elevation source.
        private readonly Uri _localElevationImageService = new Uri("https://scene.arcgis.com/arcgis/rest/services/BREST_DTM_1M/ImageServer");

        // Hold the URL to the buildings scene layer.
        private readonly Uri _buildingsUrl = new Uri("https://tiles.arcgis.com/tiles/P3ePLMYs2RVChkJx/arcgis/rest/services/Buildings_Brest/SceneServer/layers/0");

        // Hold a reference to the viewshed analysis.
        private LocationViewshed _viewshed;

        // Hold a reference to the analysis overlay that will hold the viewshed analysis.
        private AnalysisOverlay _analysisOverlay;

        // Graphics overlay for viewpoint symbol.
        private GraphicsOverlay _viewpointOverlay;

        // Symbol for viewpoint.
        private SimpleMarkerSceneSymbol _viewpointSymbol;

        // References to UI elements.
        private SeekBar _headingSlider;

        private SeekBar _pitchSlider;
        private SeekBar _horizontalAngleSlider;
        private SeekBar _verticalAngleSlider;
        private SeekBar _minimumDistanceSlider;
        private SeekBar _maximumDistanceSlider;
        private Switch _analysisVisibilitySwitch;
        private Switch _frustumVisibilitySwitch;

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

            Title = "Viewshed (Location)";

            // Create the layout
            CreateLayout();

            // Initialize the sample
            Initialize();
        }

        private void Initialize()
        {
            // Create the scene with the imagery basemap.
            Scene myScene = new Scene(BasemapStyle.ArcGISImageryStandard);
            _mySceneView.Scene = myScene;

            // Add the surface elevation.
            Surface mySurface = new Surface();
            mySurface.ElevationSources.Add(new ArcGISTiledElevationSource(_localElevationImageService));
            myScene.BaseSurface = mySurface;

            // Add the scene layer.
            ArcGISSceneLayer sceneLayer = new ArcGISSceneLayer(_buildingsUrl);
            myScene.OperationalLayers.Add(sceneLayer);

            // Create the MapPoint representing the initial location.
            MapPoint initialLocation = new MapPoint(-4.5, 48.4, 56.0);

            // Create the location viewshed analysis.
            _viewshed = new LocationViewshed(
                initialLocation,
                _headingSlider.Progress,
                _pitchSlider.Progress,
                _horizontalAngleSlider.Progress,
                _verticalAngleSlider.Progress,
                _minimumDistanceSlider.Progress,
                _maximumDistanceSlider.Progress);

            // Create a camera based on the initial location.
            Camera camera = new Camera(initialLocation, 200.0, 20.0, 70.0, 0.0);

            // Apply the camera to the scene view.
            _mySceneView.SetViewpointCamera(camera);

            // Create an analysis overlay for showing the viewshed analysis.
            _analysisOverlay = new AnalysisOverlay();

            // Add the viewshed analysis to the overlay.
            _analysisOverlay.Analyses.Add(_viewshed);

            // Create a symbol for the viewpoint.
            _viewpointSymbol = SimpleMarkerSceneSymbol.CreateSphere(System.Drawing.Color.Blue, 10, SceneSymbolAnchorPosition.Center);

            // Add the symbol to the viewpoint overlay.
            _viewpointOverlay = new GraphicsOverlay
            {
                SceneProperties = new LayerSceneProperties(SurfacePlacement.Absolute)
            };
            _viewpointOverlay.Graphics.Add(new Graphic(initialLocation, _viewpointSymbol));

            // Add the analysis overlay to the SceneView.
            _mySceneView.AnalysisOverlays.Add(_analysisOverlay);

            // Add the graphics overlay
            _mySceneView.GraphicsOverlays.Add(_viewpointOverlay);

            // Update the frustum outline color.
            // The frustum outline shows the volume in which the viewshed analysis is performed.
            Viewshed.FrustumOutlineColor = System.Drawing.Color.Blue;

            // Subscribe to tap events to enable moving the observer.
            _mySceneView.GeoViewTapped += MySceneViewOnGeoViewTapped;
        }

        private void MySceneViewOnGeoViewTapped(object sender, GeoViewInputEventArgs viewInputEventArgs)
        {
            if (viewInputEventArgs.Location == null)
            {
                // User clicked on the sky - don't update the location with invalid value.
                return;
            }
            // Update the viewshed location.
            _viewshed.Location = viewInputEventArgs.Location;

            // Move the location off of the ground.
            _viewshed.Location = new MapPoint(_viewshed.Location.X, _viewshed.Location.Y, _viewshed.Location.Z + 10.0);

            // Update the viewpoint symbol.
            _viewpointOverlay.Graphics.Clear();
            _viewpointOverlay.Graphics.Add(new Graphic(_viewshed.Location, _viewpointSymbol));
        }

        private void HandleSettingsChange(object sender, EventArgs e)
        {
            // Reset the horizontal and vertical angle if they go out of bounds
            if (_horizontalAngleSlider.Progress < 1) { _horizontalAngleSlider.Progress = 1; }
            if (_verticalAngleSlider.Progress < 1) { _verticalAngleSlider.Progress = 1; }

            // Update the viewshed settings.
            _viewshed.Heading = _headingSlider.Progress;
            _viewshed.Pitch = _pitchSlider.Progress;
            _viewshed.HorizontalAngle = _horizontalAngleSlider.Progress;
            _viewshed.VerticalAngle = _verticalAngleSlider.Progress;
            _viewshed.MinDistance = _minimumDistanceSlider.Progress + 5;
            _viewshed.MaxDistance = _maximumDistanceSlider.Progress;

            // Update visibility of the viewshed analysis.
            _viewshed.IsVisible = _analysisVisibilitySwitch.Checked;

            // Update visibility of the frustum. Note that the frustum will be invisible
            //     regardless of this setting if the viewshed analysis is not visible.
            _viewshed.IsFrustumOutlineVisible = _frustumVisibilitySwitch.Checked;
        }

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

            // Heading
            TextView headingLabel = new TextView(this) { Text = "Heading:" };
            _headingSlider = new SeekBar(this) { Max = 360 };
            layout.AddView(headingLabel);
            layout.AddView(_headingSlider);

            // Pitch
            TextView pitchLabel = new TextView(this) { Text = "Pitch:" };
            _pitchSlider = new SeekBar(this) { Max = 180, Progress = 60 };
            layout.AddView(pitchLabel);
            layout.AddView(_pitchSlider);

            // Horizontal Angle
            TextView horizontalAngleLabel = new TextView(this) { Text = "Horizontal Angle:" };
            _horizontalAngleSlider = new SeekBar(this) { Max = 120, Progress = 75 };
            layout.AddView(horizontalAngleLabel);
            layout.AddView(_horizontalAngleSlider);

            // Vertical Angle
            TextView verticalAngleLabel = new TextView(this) { Text = "Vertical Angle:" };
            _verticalAngleSlider = new SeekBar(this) { Max = 120, Progress = 90 };
            layout.AddView(verticalAngleLabel);
            layout.AddView(_verticalAngleSlider);

            // Minimum Distance
            TextView minimumDistanceLabel = new TextView(this) { Text = "Minimum Distance:" };
            _minimumDistanceSlider = new SeekBar(this) { Max = 8994 };
            layout.AddView(minimumDistanceLabel);
            layout.AddView(_minimumDistanceSlider);
            layout.SetHorizontalGravity(GravityFlags.FillHorizontal);

            // Maximum Distance
            TextView maximumDistanceLabel = new TextView(this) { Text = "Maximum Distance:" };
            _maximumDistanceSlider = new SeekBar(this) { Max = 9999, Progress = 1500 };
            layout.AddView(maximumDistanceLabel);
            layout.AddView(_maximumDistanceSlider);

            // Analysis Visibility
            TextView analysisVisibilityLabel = new TextView(this) { Text = "Analysis Visibility:" };
            _analysisVisibilitySwitch = new Switch(this) { Checked = true };
            layout.AddView(analysisVisibilityLabel);
            layout.AddView(_analysisVisibilitySwitch);

            // Frustum Visibility
            TextView frustumVisibilityLabel = new TextView(this) { Text = "Frustum Visibility:" };
            _frustumVisibilitySwitch = new Switch(this) { Checked = false };
            layout.AddView(frustumVisibilityLabel);
            layout.AddView(_frustumVisibilitySwitch);

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

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

            // Subscribe to events
            _headingSlider.ProgressChanged += HandleSettingsChange;
            _pitchSlider.ProgressChanged += HandleSettingsChange;
            _horizontalAngleSlider.ProgressChanged += HandleSettingsChange;
            _verticalAngleSlider.ProgressChanged += HandleSettingsChange;
            _minimumDistanceSlider.ProgressChanged += HandleSettingsChange;
            _maximumDistanceSlider.ProgressChanged += HandleSettingsChange;
            _analysisVisibilitySwitch.Click += HandleSettingsChange;
            _frustumVisibilitySwitch.Click += HandleSettingsChange;
        }

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

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

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