Viewshed (GeoElement)

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This sample demonstrates how to calculate a Viewshed from a GeoElement.

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.

Offline data

Offline sample data will be downloaded by the sample viewer automatically.

Link Local Location
Model Marker Symbol Data <userhome>/ArcGIS/Runtime/Data/3D/bradleylow3ds/bradle.3ds

About the data

This sample shows a Johannesburg, South Africa Scene from ArcGIS Online. The sample uses a Tank model scene symbol hosted as an item on ArcGIS Online.

Relevant API

  • AnalysisOverlay
  • GeodeticDistanceResult
  • GeoElementViewshed
  • GeometryEngine.distanceGeodetic (used to animate the vehicle)
  • ModelSceneSymbol
  • OrbitGeoElementCameraController

Tags

3D, analysis, buildings, model, scene, viewshed, visibility analysis

Sample Code

ViewshedGeoElement.qml
                                                                                                                                                                  
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// [WriteFile Name=ViewshedGeoElement, Category=Analysis]
// [Legal]
// 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.
// [Legal]

import QtQuick 2.6
import Esri.ArcGISRuntime 100.12
import Esri.ArcGISExtras 1.1

Rectangle {
    id: rootRectangle
    clip: true
    width: 800
    height: 600

    readonly property string dataPath: System.userHomePath + "/ArcGIS/Runtime/Data"
    readonly property string headingAttr: "HEADING"
    readonly property var linearUnit: Enums.LinearUnitIdMeters
    readonly property var angularUnit: Enums.AngularUnitIdDegrees
    readonly property var geodeticCurveType: Enums.GeodeticCurveTypeGeodesic
    property Point waypoint: null

    SceneView {
        id: sceneView
        anchors.fill: parent

        Scene {
            id: scene
            Basemap {
                initStyle: Enums.BasemapStyleArcGISImageryStandard
            }

            // Set the Scene's Surface
            Surface {
                ArcGISTiledElevationSource {
                    url: "https://scene.arcgis.com/arcgis/rest/services/BREST_DTM_1M/ImageServer"
                }
            }

            // Add a Scene Layer
            ArcGISSceneLayer {
                url: "https://tiles.arcgis.com/tiles/P3ePLMYs2RVChkJx/arcgis/rest/services/Buildings_Brest/SceneServer/layers/0"
            }

            onLoadStatusChanged: {
                if (loadStatus !== Enums.LoadStatusLoaded)
                    return;

                // Set the Camera Controller
                const controller = ArcGISRuntimeEnvironment.createObject("OrbitGeoElementCameraController", {
                                                                             targetGeoElement: tank, cameraDistance: 200,
                                                                             cameraPitchOffset: 45
                                                                         });
                sceneView.cameraController = controller;
            }
        }

        // Declare a GraphicsOverlay
        GraphicsOverlay {

            SimpleRenderer {
                // set up heading expression for the tank
                RendererSceneProperties {
                    headingExpression: "[%1]".arg(headingAttr)
                }
            }

            LayerSceneProperties {
                surfacePlacement: Enums.SurfacePlacementRelative
            }

            // Create the Tank Graphic
            Graphic {
                id: tank

                Point {
                    x: -4.508708007847015
                    y: 48.38823243446344
                    z: 0
                    spatialReference: Factory.SpatialReference.createWgs84()
                }

                ModelSceneSymbol {
                    id: sceneSymbol
                    url: dataPath + "/3D/bradley_low_3ds/bradle.3ds"
                    anchorPosition: Enums.SceneSymbolAnchorPositionBottom
                    scale: 10
                    heading: 90.0
                }

                Component.onCompleted: {
                    tank.attributes.insertAttribute(headingAttr, 150.0)
                }
            }
        }

        // Declare an Analysis Overlay
        AnalysisOverlay {
            id: analysisOverlay

            // Create the Location Viewshed
            GeoElementViewshed {
                id: geoelementViewshed
                horizontalAngle: 90.0
                verticalAngle: 25.0
                minDistance: 5.0
                maxDistance: 250.0
                headingOffset: 0
                pitchOffset: 0
                offsetY: 0.5
                offsetZ: 0.5
                geoElement: tank
            }
        }

        onMouseClicked: {
            waypoint = sceneView.screenToBaseSurface(mouse.x, mouse.y);
            timer.start();
        }
    }

    function animate() {
        if (waypoint === null)
            return;

        // get current location and distance from waypoint
        let location = tank.geometry;
        const distance = GeometryEngine.distanceGeodetic(location, waypoint, linearUnit, angularUnit, geodeticCurveType);

        // move toward waypoint based on speed and update orientation
        location = GeometryEngine.moveGeodetic([location], 1.0, linearUnit, distance.azimuth1, angularUnit, geodeticCurveType);
        tank.geometry = location[0];

        // update the heading
        const heading = tank.attributes.attributeValue(headingAttr);
        tank.attributes.replaceAttribute(headingAttr, heading + (distance.azimuth1 - heading) / 10);

        // reached waypoint
        if (distance.distance <= 5) {
            waypoint = null;
            timer.stop();
        }
    }

    Timer {
        id: timer
        interval: 100
        repeat: true
        onTriggered: animate()
    }
}

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