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156 lines
7.1 KiB
Markdown
156 lines
7.1 KiB
Markdown
# Creating a location provider for ArcGIS Runtime SDK
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Below is an implementation for use with the [ArcGIS Runtime SDK for .NET](http://developers.arcgis.com/net). Use this location provider on the MapView's LocationDisplay to send it location data from your NMEA device to display your current location on a map.
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Below is an example implementation of this.
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You can also check out the Desktop Sample app in the [Github Repo]( https://github.com/dotMorten/NmeaParser/blob/main/src/SampleApp.WinDesktop/NmeaProvider.cs) which uses this to display a map.
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**Usage:**
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```csharp
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NmeaParser.NmeaDevice device = new NmeaParser.NmeaFileDevice("NmeaSampleData.txt");
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mapView.LocationDisplay.DataSource = new NmeaLocationProvider(device);
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mapView.LocationDisplay.InitialZoomScale = 20000;
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mapView.LocationDisplay.IsEnabled = true;
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```
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**NmeaLocationProvider.cs**
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```csharp
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using System.Threading.Tasks;
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using Esri.ArcGISRuntime.Geometry;
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using Esri.ArcGISRuntime.Location;
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using NmeaParser;
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namespace NmeaParser.ArcGIS
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{
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public class NmeaLocationProvider : LocationDataSource
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{
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private readonly NmeaParser.NmeaDevice device;
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public NmeaLocationProvider(NmeaParser.NmeaDevice device)
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{
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this.device = device;
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device.MessageReceived += NmeaMessageReceived;
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}
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private void NmeaMessageReceived(object sender, NmeaMessageReceivedEventArgs e)
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{
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var message = e.Message;
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if (message is NmeaParser.Messages.Rmc rmc && rmc.Active)
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{
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base.UpdateLocation(new Location(
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new MapPoint(rmc.Longitude, rmc.Latitude, SpatialReferences.Wgs84),
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horizontalAccuracy: double.NaN,
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velocity: double.IsNaN(rmc.Speed) ? 0 : rmc.Speed,
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course: double.IsNaN(rmc.Course) ? 0 : rmc.Course, // Current ArcGIS Runtime limitation that course can't be NaN
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isLastKnown: false));
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}
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}
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protected override Task OnStartAsync() => device.OpenAsync();
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protected override Task OnStopAsync() => device.CloseAsync();
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}
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}
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```
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### Combining multiple NMEA messages into a single location event
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NMEA often happens in a burst of messages, which could be combined to one larger location object with more information available, as well as containing information from multiple different satellite systems.
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By using the `GnssMonitor` class that aggregates these messages, we can create a much more robust location provider:
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```
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using System;
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using System.Threading.Tasks;
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using Esri.ArcGISRuntime.Geometry;
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using NmeaParser.Gnss;
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namespace NmeaParser.ArcGIS
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{
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public class NmeaLocationDataSource : Esri.ArcGISRuntime.Location.LocationDataSource
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{
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private static SpatialReference wgs84_ellipsoidHeight = SpatialReference.Create(4326, 115700);
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private readonly GnssMonitor m_gnssMonitor;
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private readonly bool m_startStopDevice;
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private double lastCourse = 0; // Course can fallback to NaN, but ArcGIS Datasource don't allow NaN course, so we cache last known as a fallback
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/// <summary>
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/// Initializes a new instance of the <see cref="NmeaLocationDataSource"/> class.
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/// </summary>
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/// <param name="device">The NMEA device to monitor</param>
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/// <param name="startStopDevice">Whether starting this datasource also controls the underlying NMEA device</param>
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public NmeaLocationDataSource(NmeaParser.NmeaDevice device, bool startStopDevice = true) : this(new GnssMonitor(device), startStopDevice)
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{
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}
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/// <summary>
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/// Initializes a new instance of the <see cref="NmeaLocationDataSource"/> class.
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/// </summary>
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/// <param name="monitor">The NMEA device to monitor</param>
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/// <param name="startStopDevice">Whether starting this datasource also controls the underlying NMEA device</param>
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public NmeaLocationDataSource(NmeaParser.Gnss.GnssMonitor monitor, bool startStopDevice = true)
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{
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if (monitor == null)
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throw new ArgumentNullException(nameof(monitor));
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this.m_gnssMonitor = monitor;
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m_startStopDevice = startStopDevice;
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}
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protected async override Task OnStartAsync()
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{
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m_gnssMonitor.LocationChanged += OnLocationChanged;
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m_gnssMonitor.LocationLost += OnLocationChanged;
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if (m_startStopDevice && !this.m_gnssMonitor.Device.IsOpen)
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await this.m_gnssMonitor.Device.OpenAsync();
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if (m_gnssMonitor.IsFixValid)
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OnLocationChanged(this, EventArgs.Empty);
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}
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protected override Task OnStopAsync()
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{
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m_gnssMonitor.LocationChanged -= OnLocationChanged;
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m_gnssMonitor.LocationLost -= OnLocationChanged;
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if(m_startStopDevice)
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return m_gnssMonitor.Device.CloseAsync();
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else
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return Task.CompletedTask;
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}
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private Esri.ArcGISRuntime.Location.Location currentLocation;
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private void OnLocationChanged(object sender, EventArgs e)
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{
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if (double.IsNaN(m_gnssMonitor.Longitude) || double.IsNaN(m_gnssMonitor.Latitude)) return;
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if (!double.IsNaN(m_gnssMonitor.Course))
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lastCourse = m_gnssMonitor.Course;
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DateTimeOffset? timestamp = null;
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if(m_gnssMonitor.FixTime.HasValue)
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timestamp = new DateTimeOffset(DateTime.UtcNow.Date.Add(m_gnssMonitor.FixTime.Value));
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var location = new Esri.ArcGISRuntime.Location.Location(
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timestamp: timestamp,
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position: !double.IsNaN(m_gnssMonitor.Altitude) ? new MapPoint(m_gnssMonitor.Longitude, m_gnssMonitor.Latitude, m_gnssMonitor.Altitude, wgs84_ellipsoidHeight) : new MapPoint(m_gnssMonitor.Longitude, m_gnssMonitor.Latitude, SpatialReferences.Wgs84),
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horizontalAccuracy: m_gnssMonitor.HorizontalError,
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verticalAccuracy: m_gnssMonitor.VerticalError,
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velocity: double.IsNaN(m_gnssMonitor.Speed) ? 0 : m_gnssMonitor.Speed * 0.51444444,
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course: lastCourse,
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!m_gnssMonitor.IsFixValid);
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// Avoid raising additional location events if nothing changed
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if (currentLocation == null ||
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currentLocation.Position.X != location.Position.X ||
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currentLocation.Position.Y != location.Position.Y ||
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currentLocation.Position.Z != location.Position.Z ||
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currentLocation.Course != location.Course ||
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currentLocation.Velocity != location.Velocity ||
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currentLocation.HorizontalAccuracy != location.HorizontalAccuracy ||
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currentLocation.VerticalAccuracy != location.VerticalAccuracy ||
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currentLocation.IsLastKnown != location.IsLastKnown ||
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timestamp != location.Timestamp)
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{
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currentLocation = location;
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UpdateLocation(currentLocation);
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}
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}
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}
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}
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```
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