private void DrawSphere()
        {
            // create a new point (MapPoint); pass x, y, and z coordinates in the constructor
            var point = new MapPoint(-122.4167, 37.7833, 6000);

            // create a graphics layer
            GraphicsLayer graphicsLayer = new GraphicsLayer();

            graphicsLayer.ID = "Graphics Layer";
            graphicsLayer.SceneProperties.SurfacePlacement =
                SurfacePlacement.Absolute;
            graphicsLayer.InitializeAsync();

            // creates a red sphere with a radius of 20,000 meters
            var sphereSym = new SphereMarkerSymbol();

            sphereSym.Color = Colors.Red;

            sphereSym.Radius = 20000;

            // create the graphic
            var graphic = new Graphic(point, sphereSym);

            graphicsLayer.Graphics.Add(graphic);

            // add the graphics layers to the scene
            this.sceneView.Scene.Layers.Add(graphicsLayer);
        }
        private void DrawSphere()
        {
            // create a new point (MapPoint); pass x, y, and z coordinates in the constructor
            var point = new MapPoint(-122.4167, 37.7833,  6000);

            // create a graphics layer
            GraphicsLayer graphicsLayer = new GraphicsLayer();
            graphicsLayer.ID = "Graphics Layer";
            graphicsLayer.SceneProperties.SurfacePlacement =
                                SurfacePlacement.Absolute;
            graphicsLayer.InitializeAsync();

            // creates a red sphere with a radius of 20,000 meters
            var sphereSym = new SphereMarkerSymbol();
            sphereSym.Color = Colors.Red;

            sphereSym.Radius = 20000;

            // create the graphic
            var graphic = new Graphic(point, sphereSym);
           
            graphicsLayer.Graphics.Add(graphic);

            // add the graphics layers to the scene
            this.sceneView.Scene.Layers.Add(graphicsLayer);
        }