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Added ntrip doc
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Morten Nielsen
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docs/concepts/ntrip.md
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211
docs/concepts/ntrip.md
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#Using NTRIP for DGPS
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You can use data from a nearby NTRIP server to improve the accuracy if your GPS position, if your device supports it.
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The Serial and Bluetooth devices supports writing to them, so you merely need to stream the data from the NTRIP server directly to your device.
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We'll first create a simple NTRIP client library:
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```cs
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using System;
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using System.Collections.Generic;
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using System.Globalization;
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using System.Linq;
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using System.Net;
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using System.Net.Sockets;
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using System.Threading.Tasks;
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namespace Ntrip
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{
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public abstract class NtripSource
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{
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}
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public class Caster : NtripSource
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{
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public IPAddress Address { get; set; }
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public int Port { get; set; }
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public string Identifier { get; set; }
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public string Operator { get; set; }
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public bool SupportsNmea { get; set; }
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public string CountryCode { get; set; }
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public double Latitude { get; set; }
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public double Longitude { get; set; }
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public IPAddress FallbackAddress { get; set; }
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}
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public class NtripStream : NtripSource
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{
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public string Mountpoint { get; set; }
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public string Identifier { get; set; }
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public string Format { get; set; }
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public string FormatDetails { get; set; }
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public Carrier Carrier { get; set; }
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public string Network { get; set; }
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public string CountryCode { get; set; }
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public double Latitude { get; set; }
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public double Longitude { get; set; }
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public bool SupportsNmea { get; set; }
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}
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public enum Carrier : int
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{
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No = 0,
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L1 = 1,
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L1L2 = 2
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}
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public class Client : IDisposable
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{
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private readonly string _host;
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private readonly int _port;
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private string _auth;
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private Socket sckt;
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public Client(string host, int port, string authKey = null)
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{
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_host = host;
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_port = port;
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_auth = authKey;
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}
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public IEnumerable<NtripSource> GetSourceTable()
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{
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string data = "";
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byte[] buffer = new byte[1024];
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using (var sck = Request(""))
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{
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int count;
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while ((count = sck.Receive(buffer)) > 0)
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{
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data += System.Text.Encoding.UTF8.GetString(buffer, 0, count);
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}
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}
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var lines = data.Split('\n');
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List<NtripSource> sources = new List<NtripSource>();
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foreach (var item in lines)
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{
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var d = item.Split(';');
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if (d.Length == 0) continue;
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if (d[0] == "ENDSOURCETABLE")
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break;
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if (d[0] == "CAS")
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{
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var c = new Caster();
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var a = d[1].Split(':');
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c.Address = IPAddress.Parse(a[0]);
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c.Port = int.Parse(a[1]);
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c.Identifier = d[3];
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c.Operator = d[4];
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c.SupportsNmea = d[5] == "1";
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c.CountryCode = d[6];
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c.Latitude = double.Parse(d[7], CultureInfo.InvariantCulture);
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c.Longitude = double.Parse(d[8], CultureInfo.InvariantCulture);
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c.FallbackAddress = IPAddress.Parse(d[9]);
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sources.Add(c);
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}
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else if (d[0] == "STR")
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{
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var str = new NtripStream();
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str.Mountpoint = d[1];
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str.Identifier = d[2];
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str.Format = d[3];
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str.FormatDetails = d[4];
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str.Carrier = (Carrier)int.Parse(d[5]);
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str.Network = d[7];
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str.CountryCode = d[8];
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str.Latitude = double.Parse(d[9], CultureInfo.InvariantCulture);
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str.Longitude = double.Parse(d[10], CultureInfo.InvariantCulture);
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str.SupportsNmea = d[11] == "1";
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sources.Add(str);
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}
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}
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return sources;
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}
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private Socket Request(string path)
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{
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var sckt = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
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sckt.Blocking = true;
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sckt.Connect(_host, _port);
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string msg = $"GET /{path} HTTP/1.1\r\n";
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msg += "User-Agent: NTRIP ntripclient\r\n";
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if (_auth != null)
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{
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msg += "Authorization: Basic " + _auth + "\r\n";
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}
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msg += "Accept: */*\r\nConnection: close\r\n";
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msg += "\r\n";
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byte[] data = System.Text.Encoding.ASCII.GetBytes(msg);
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sckt.Send(data);
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return sckt;
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}
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public void Connect(string strName)
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{
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if (sckt != null) throw new Exception("Connection already open");
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sckt = Request(strName);
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connected = true;
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runningTask = Task.Run(ReceiveThread);
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}
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private bool connected;
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private Task runningTask;
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private async Task ReceiveThread()
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{
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byte[] buffer = new byte[65536];
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while (connected)
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{
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int count = sckt.Receive(buffer);
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if(count > 0)
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{
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DataReceived?.Invoke(this, buffer.Take(count).ToArray());
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}
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await Task.Delay(10);
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}
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sckt.Shutdown(SocketShutdown.Both);
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sckt.Close();
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sckt = null;
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}
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public Task CloseAsync()
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{
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if (runningTask != null)
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{
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connected = false;
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var t = runningTask;
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runningTask = null;
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return t;
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}
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return Task.CompletedTask;
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}
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public void Dispose()
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{
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_ = CloseAsync();
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}
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public event EventHandler<byte[]> DataReceived;
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}
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}
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```
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You can next connect to your NTRIP server, pick a stream and start streaming it to your device.
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Example:
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```cs
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string hostname = "esricaster.esri.com"; // Replace with a server near you
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int port = 2101; //Port for the ntrip server
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var client = new Ntrip.Client(hostname, port);
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// Get the source table from the server:
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var table = client.GetSourceTable();
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// Just pick the first Ntrip datastream:
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var str = table.OfType<NtripStream>().First();
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// Listen for data, and simply forward it to the NMEA device:
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client.DataReceived += (sender, ntripData) => {
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nmeaDevice.WriteAsync(ntripData, 0, ntripData.Length);
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};
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// Connect to the stream
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client.Connect(str.Mountpoint);
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```
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@ -30,5 +30,7 @@
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href: CustomMessages.md
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- name: Creating a location provider for ArcGIS Runtime SDK
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href: ArcGISRuntime.md
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- name: Using NTRIP for DGPS
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href: ntrip.md
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- name: Object Model Diagram
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href: ../api/omd.html
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