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193 lines
7.8 KiB
Markdown
193 lines
7.8 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.
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By relying on the time stamp in most of the messages, we can combine them all to get better metadata about the location.
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```
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using System;
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using System.Linq;
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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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using NmeaParser.Messages;
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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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private Gga lastGga;
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private Rmc lastRmc;
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private Gsa lastGsa;
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private Gst lastGst;
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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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bool newFix = false;
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if (message is Rmc rmc && rmc.Active)
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{
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lastRmc = rmc;
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newFix = true;
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}
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else if (message is Gga gga)
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{
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lastGga = gga;
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newFix = true;
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}
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else if (message is Gst gst)
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{
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lastGst = gst;
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newFix = true;
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}
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else if (message is Gsa gsa)
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{
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lastGsa = gsa;
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}
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else
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{
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return;
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}
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// We require the timestamps to match to raise them together. Gsa doesn't have a time stamp so just using latest for that
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TimeSpan? timeOfFixMax = MaxTime(lastRmc?.FixTime.TimeOfDay, lastGga?.FixTime, lastGst?.FixTime);
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TimeSpan? timeOfFixMin = MinTime(lastRmc?.FixTime.TimeOfDay, lastGga?.FixTime, lastGst?.FixTime);
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if (newFix && timeOfFixMax == timeOfFixMin)
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{
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var location = NmeaLocation.Create(timeOfFixMax.Value, lastRmc, lastGga, lastGsa, lastGst);
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if (location != null)
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base.UpdateLocation(location);
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}
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}
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private static TimeSpan? MaxTime(params TimeSpan?[] timeSpans) => timeSpans.Where(t => t != null).Max();
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private static TimeSpan? MinTime(params TimeSpan?[] timeSpans) => timeSpans.Where(t => t != null).Min();
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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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/// <summary>
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/// Custom location class with the additional NMEA information associated with it
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/// </summary>
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public class NmeaLocation : Location
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{
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private NmeaLocation(DateTimeOffset? timestamp, MapPoint position, double horizontalAccuracy, double verticalAccuracy, double velocity, double course, bool isLastKnown)
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: base(timestamp, position, horizontalAccuracy, verticalAccuracy, velocity, course, isLastKnown)
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{
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}
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public static NmeaLocation Create(TimeSpan timeOfFix, Rmc rmc, Gga gga, Gsa gsa, Gst gst)
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{
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MapPoint position = null;
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double horizontalAccuracy = double.NaN;
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double verticalAccuracy = double.NaN;
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double velocity = 0;
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double course = 0;
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// Prefer GGA over RMC for location
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if (gga != null && gga.FixTime == timeOfFix)
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{
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if (double.IsNaN(gga.Altitude))
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position = new MapPoint(gga.Longitude, gga.Latitude, SpatialReferences.Wgs84);
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else
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{
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// Vertical id 115700 == ellipsoid reference system. Gga is geoid, but we subtract GeoidalSeparation to simplify
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// vertical transformations from the simpler/better known ellipsoidal model
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position = new MapPoint(gga.Longitude, gga.Latitude, gga.Altitude + gga.GeoidalSeparation, SpatialReference.Create(4326, 115700));
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}
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}
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if (rmc != null && rmc.FixTime.TimeOfDay == timeOfFix)
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{
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if (position == null)
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{
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position = new MapPoint(rmc.Longitude, rmc.Latitude, SpatialReferences.Wgs84);
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}
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velocity = double.IsNaN(rmc.Speed) ? 0 : rmc.Speed;
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course = double.IsNaN(rmc.Course) ? 0 : rmc.Course;
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}
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if (gst != null && gst.FixTime == timeOfFix)
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{
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verticalAccuracy = gst.SigmaHeightError;
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horizontalAccuracy = gst.SemiMajorError;
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}
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if (position == null)
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return null;
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var location = new NmeaLocation(DateTimeOffset.UtcNow.Date.Add(timeOfFix), position, horizontalAccuracy, verticalAccuracy, velocity, course, false);
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location.Rmc = rmc;
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location.Gga = gga;
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location.Gsa = gsa;
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location.Gst = gst?.FixTime == timeOfFix ? gst : null;
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return location;
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}
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public Rmc Rmc { get; private set; }
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public Gga Gga { get; private set; }
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public Gsa Gsa { get; private set; }
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public Gst Gst { get; private set; }
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public int NumberOfSatellites => Gga?.NumberOfSatellites ?? -1;
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public double Hdop => Gsa?.Hdop ?? Gga?.Hdop ?? double.NaN;
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public double Pdop => Gsa?.Pdop ?? double.NaN;
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public double Vdop => Gsa?.Vdop ?? double.NaN;
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}
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}
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```
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