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ArcGIS Runtime SDK for .NET

Viewshed for GeoElement

This code sample is available for these platforms:
View Sample on GitHub

Analyze the viewshed for an object (GeoElement) in a scene.

screenshot

Use case

A Viewshed analysis is a type of visual analysis you can perform on a scene. The viewshed aims to answer the question 'What can I see 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).

How to use the sample

Tap to set a destination for the vehicle (a GeoElement). The vehicle will 'drive' towards the tapped location. The viewshed analysis will update as the vehicle moves.

How it works

  1. Create and show the scene, with an elevation source and a buildings layer.
  2. Add a model (the GeoElement) to represent the observer (in this case, a tank).
    • Use a SimpleRenderer which has a heading expression set in the GraphicsOverlay. This way you can relate the viewshed's heading to the GeoElement object's heading.
  3. Create a GeoElementViewshed with configuration for the viewshed analysis.
  4. Add the viewshed to an AnalysisOverlay and add the overlay to the scene.
  5. Configure the SceneView CameraController to orbit the vehicle.

Relevant API

  • AnalysisOverlay
  • GeoElementViewshed
  • GeodeticDistanceResult
  • GeometryEngine.DistanceGeodetic - used to animate the vehicle.
  • ModelSceneSymbol
  • OrbitGeoElementCameraController

Offline data

This sample downloads the following items from ArcGIS Online automatically:

About the data

This sample shows a Johannesburg building layer from ArcGIS Online. The vehicle is a tank.

Tags

3D, AnalysisOverlay, GeoElementViewshed, ModelSceneSymbol, OrbitGeoElementCameraController, SceneProperties, buildings, model, scene, viewshed, visibility analysis

Sample Code

<UserControl
    x:Class="ArcGISRuntime.UWP.Samples.ViewshedGeoElement.ViewshedGeoElement"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:esriUI="using:Esri.ArcGISRuntime.UI.Controls">
    <Grid>
        <esriUI:SceneView x:Name="MySceneView" />
        <Border Style="{StaticResource BorderStyle}">
            <TextBlock Text="Tap to set a destination for the vehicle."
                       TextAlignment="Center"
                       FontWeight="SemiBold" />
        </Border>
    </Grid>
</UserControl>
// 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.

using ArcGISRuntime.Samples.Managers;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Symbology;
using Esri.ArcGISRuntime.UI;
using Esri.ArcGISRuntime.UI.GeoAnalysis;
using System;
using System.Collections.Generic;
using System.Linq;
using Windows.UI.Popups;
using Windows.UI.Xaml;

namespace ArcGISRuntime.UWP.Samples.ViewshedGeoElement
{
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        "Viewshed (GeoElement)",
        "Analysis",
        "Display a live viewshed analysis for a moving GeoElement.",
        "Tap on the scene to see the tank move to that point.",
        "Featured")]
	[ArcGISRuntime.Samples.Shared.Attributes.OfflineData("07d62a792ab6496d9b772a24efea45d0")]
    public partial class ViewshedGeoElement
    {
        // URLs to the scene layer with buildings and the elevation source
        private readonly Uri _elevationUri = new Uri("https://elevation3d.arcgis.com/arcgis/rest/services/WorldElevation3D/Terrain3D/ImageServer");
        private readonly Uri _buildingsUri = new Uri("https://tiles.arcgis.com/tiles/P3ePLMYs2RVChkJx/arcgis/rest/services/Building_Johannesburg/SceneServer");

        // Graphic and overlay for showing the tank
        private readonly GraphicsOverlay _tankOverlay = new GraphicsOverlay();
        private Graphic _tank;

        // Animation properties
        private MapPoint _tankEndPoint;

        // Units for geodetic calculation (used in animating tank)
        private readonly LinearUnit _metersUnit = (LinearUnit)Unit.FromUnitId(9001);
        private readonly AngularUnit _degreesUnit = (AngularUnit)Unit.FromUnitId(9102);

        public ViewshedGeoElement()
        {
            InitializeComponent();

            // Setup the control references and execute initialization
            Initialize();
        }

        private async void Initialize()
        {
            // Create the scene with an imagery basemap.
            MySceneView.Scene = new Scene(Basemap.CreateImagery());

            // Add the elevation surface.
            ArcGISTiledElevationSource tiledElevationSource = new ArcGISTiledElevationSource(_elevationUri);
            Surface baseSurface = new Surface
            {
                ElevationSources = { tiledElevationSource }
            };
            MySceneView.Scene.BaseSurface = baseSurface;

            // Add buildings.
            ArcGISSceneLayer sceneLayer = new ArcGISSceneLayer(_buildingsUri);
            MySceneView.Scene.OperationalLayers.Add(sceneLayer);

            // Configure graphics overlay for the tank and add the overlay to the SceneView.
            _tankOverlay.SceneProperties.SurfacePlacement = SurfacePlacement.Relative;
            MySceneView.GraphicsOverlays.Add(_tankOverlay);

            // Configure heading expression for tank; this will allow the
            //     viewshed to update automatically based on the tank's position.
            SimpleRenderer renderer3D = new SimpleRenderer();
            renderer3D.SceneProperties.HeadingExpression = "[HEADING]";
            _tankOverlay.Renderer = renderer3D;

            try
            {
                // Create the tank graphic - get the model path.
                string modelPath = GetModelPath();
                // - Create the symbol and make it 10x larger (to be the right size relative to the scene).
                ModelSceneSymbol tankSymbol = await ModelSceneSymbol.CreateAsync(new Uri(modelPath), 10);
                // - Adjust the position.
                tankSymbol.Heading = 90;
                // - The tank will be positioned relative to the scene surface by its bottom.
                //       This ensures that the tank is on the ground rather than partially under it.
                tankSymbol.AnchorPosition = SceneSymbolAnchorPosition.Bottom;
                // - Create the graphic.
                _tank = new Graphic(new MapPoint(28.047199, -26.189105, SpatialReferences.Wgs84), tankSymbol);
                // - Update the heading.
                _tank.Attributes["HEADING"] = 0.0;
                // - Add the graphic to the overlay.
                _tankOverlay.Graphics.Add(_tank);

                // Create a viewshed for the tank.
                GeoElementViewshed geoViewshed = new GeoElementViewshed(
                    geoElement: _tank,
                    horizontalAngle: 90.0,
                    verticalAngle: 40.0,
                    minDistance: 0.1,
                    maxDistance: 250.0,
                    headingOffset: 0.0,
                    pitchOffset: 0.0)
                {
                    // Offset viewshed observer location to top of tank.
                    OffsetZ = 3.0
                };

                // Create the analysis overlay and add to the scene.
                AnalysisOverlay overlay = new AnalysisOverlay();
                overlay.Analyses.Add(geoViewshed);
                MySceneView.AnalysisOverlays.Add(overlay);

                // Create a camera controller to orbit the tank.
                OrbitGeoElementCameraController cameraController = new OrbitGeoElementCameraController(_tank, 200.0)
                {
                    CameraPitchOffset = 45.0
                };
                // - Apply the camera controller to the SceneView.
                MySceneView.CameraController = cameraController;

                // Create a timer; this will enable animating the tank.
                DispatcherTimer animationTimer = new DispatcherTimer()
                {
                    Interval = new TimeSpan(0, 0, 0, 0, 60)
                };
                // - Move the tank every time the timer expires.
                animationTimer.Tick += (o, e) => { AnimateTank(); };
                // - Start the timer.
                animationTimer.Start();

                // Allow the user to click to define a new destination.
                MySceneView.GeoViewTapped += (sender, args) => { _tankEndPoint = args.Location; };
            }
            catch (Exception e)
            {
                await new MessageDialog(e.ToString(), "Error").ShowAsync();
            }
        }

        private void AnimateTank()
        {
            // Return if the tank already arrived.
            if (_tankEndPoint == null)
            {
                return;
            }

            // Get the current location and distance from the destination.
            MapPoint location = (MapPoint)_tank.Geometry;
            GeodeticDistanceResult distance = GeometryEngine.DistanceGeodetic(
                location, _tankEndPoint, _metersUnit, _degreesUnit, GeodeticCurveType.Geodesic);

            // Move the tank a short distance.
            location = GeometryEngine.MoveGeodetic(new List<MapPoint>() { location }, 1.0, _metersUnit, distance.Azimuth1, _degreesUnit,
                GeodeticCurveType.Geodesic).First();
            _tank.Geometry = location;

            // Rotate to face the destination.
            double heading = (double)_tank.Attributes["HEADING"];
            heading = heading + (distance.Azimuth1 - heading) / 10;
            _tank.Attributes["HEADING"] = heading;

            // Clear the destination if the tank already arrived.
            if (distance.Distance < 5)
            {
                _tankEndPoint = null;
            }
        }

        private static string GetModelPath()
        {
            // Returns the tank model.
            return DataManager.GetDataFolder("07d62a792ab6496d9b772a24efea45d0", "bradle.3ds");
        }
    }
}