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ArcGIS Runtime SDK for .NET

Nearest vertex

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

Shows how to find the nearest vertex on a geometry to a given point.

screenshot

How to use the sample

Tap anywhere on the map. An orange marker will show the tapped location. A blue marker will show the polygon's nearest vertex to the tapped location. A red marker will show the nearest coordinate on the geometry.

How it works

  1. Get a Point to check the nearest vertex against.
  2. Call GeometryEngine.NearestVertex(inputGeometry, point). The returned ProximityResult can be used to get the coordinate and distance between the vertex and point.
  3. Call GeometryEngine.NearestCoordinate(inputGeometry, point). The returned ProximityResult can be used to get the coordinate and distance between the coordinate and point.

Relevant API

  • GeometryEngine
  • ProximityResult

Tags

Analysis, Geometry

Sample Code

<UserControl
    x:Class="ArcGISRuntime.UWP.Samples.NearestVertex.NearestVertex"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:controls="using:Esri.ArcGISRuntime.UI.Controls">
    <Grid>
        <controls:MapView x:Name="MyMapView" />
        <Border Style="{StaticResource BorderStyle}">
            <StackPanel>
                <TextBlock x:Name="ResultsLabel"
                           Text="Tap to see the nearest vertex and point."
                           FontWeight="SemiBold" TextAlignment="Center" />
            </StackPanel>
        </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 Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Symbology;
using Esri.ArcGISRuntime.UI;
using Esri.ArcGISRuntime.UI.Controls;

namespace ArcGISRuntime.UWP.Samples.NearestVertex
{
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        "Nearest vertex",
        "Geometry",
        "This sample demonstrates how to use the Geometry engine find the nearest vertex and nearest coordinate of a polygon to a point. The distance for each is shown.",
        "Tap on the map. The nearest point/coordinate and nearest vertex in the polygon will be shown.")]
    public partial class NearestVertex
    {
        // Hold references to the graphics overlay and the polygon graphic
        private GraphicsOverlay _graphicsOverlay;
        private Graphic _polygonGraphic;

        // Hold references to the graphics for the user and results points
        private Graphic _tappedLocationGraphic;
        private Graphic _nearestVertexGraphic;
        private Graphic _nearestCoordinateGraphic;

        public NearestVertex()
        {
            InitializeComponent();

            // Create the map, set the initial extent, and add the original point graphic.
            Initialize();
        }

        private void Initialize()
        {
            // Configure the basemap
            MyMapView.Map = new Map(Basemap.CreateTopographic());

            // Create the graphics overlay and set the selection color
            _graphicsOverlay = new GraphicsOverlay();

            // Add the overlay to the MapView
            MyMapView.GraphicsOverlays.Add(_graphicsOverlay);

            // Create the point collection that defines the polygon
            PointCollection polygonPoints = new PointCollection(SpatialReferences.WebMercator)
            {
                new MapPoint(-5991501.677830, 5599295.131468),
                new MapPoint(-6928550.398185, 2087936.739807),
                new MapPoint(-3149463.800709, 1840803.011362),
                new MapPoint(-1563689.043184, 3714900.452072),
                new MapPoint(-3180355.516764, 5619889.608838)
            };

            // Create the polygon
            Polygon polygonGeometry = new Polygon(polygonPoints);

            // Define and apply the symbology
            SimpleLineSymbol polygonOutlineSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Solid, System.Drawing.Color.Green, 2);
            SimpleFillSymbol polygonFillSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle.ForwardDiagonal, System.Drawing.Color.Green, polygonOutlineSymbol);

            // Create the graphic and add it to the graphics overlay
            _polygonGraphic = new Graphic(polygonGeometry, polygonFillSymbol);
            _graphicsOverlay.Graphics.Add(_polygonGraphic);

            // Create the graphics and symbology for the tapped point, the nearest vertex, and the nearest coordinate
            SimpleMarkerSymbol tappedLocationSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle.X, System.Drawing.Color.Orange, 15);
            SimpleMarkerSymbol nearestCoordinateSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle.Diamond, System.Drawing.Color.Red, 10);
            SimpleMarkerSymbol nearestVertexSymbol = new SimpleMarkerSymbol(SimpleMarkerSymbolStyle.Circle, System.Drawing.Color.Blue, 15);
            _nearestCoordinateGraphic = new Graphic { Symbol = nearestCoordinateSymbol };
            _tappedLocationGraphic = new Graphic { Symbol = tappedLocationSymbol };
            _nearestVertexGraphic = new Graphic { Symbol = nearestVertexSymbol };
            
            _graphicsOverlay.Graphics.Add(_tappedLocationGraphic);
            _graphicsOverlay.Graphics.Add(_nearestVertexGraphic);
            _graphicsOverlay.Graphics.Add(_nearestCoordinateGraphic);

            // Listen for taps; the spatial relationships will be updated in the handler
            MyMapView.GeoViewTapped += MapViewTapped;

            // Center the map on the polygon
            // Create the point that defines the point graphic
            MapPoint centerPoint = new MapPoint(-4487263.495911, 3699176.480377, SpatialReferences.WebMercator);
            MyMapView.SetViewpointCenterAsync(centerPoint, 200000000);
        }

        private void MapViewTapped(object sender, GeoViewInputEventArgs geoViewInputEventArgs)
        {
            // Get the tapped location
            MapPoint tappedLocation = geoViewInputEventArgs.Location;

            // Show the tapped location
            _tappedLocationGraphic.Geometry = tappedLocation;

            // Get the nearest vertex in the polygon
            ProximityResult nearestVertexResult = GeometryEngine.NearestVertex(_polygonGraphic.Geometry, tappedLocation);

            // Get the nearest coordinate in the polygon
            ProximityResult nearestCoordinateResult =
                GeometryEngine.NearestCoordinate(_polygonGraphic.Geometry, tappedLocation);

            // Get the distance to the nearest vertex in the polygon
            int distanceVertex = (int)(nearestVertexResult.Distance / 1000);

            // Get the distance to the nearest coordinate in the polygon
            int distanceCoordinate = (int)(nearestCoordinateResult.Distance / 1000);

            // Show the nearest vertex in blue
            _nearestVertexGraphic.Geometry = nearestVertexResult.Coordinate;

            // Show the nearest coordinate in red
            _nearestCoordinateGraphic.Geometry = nearestCoordinateResult.Coordinate;

            // Show the distances in the UI
            ResultsLabel.Text = $"Vertex dist: {distanceVertex} km, Point dist: {distanceCoordinate} km";
        }
    }
}