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Your first simulated voyage

In this tutorial you start the desktop application, watch it emit NMEA 0183 sentences, steer the vessel from the keyboard and connect a chart plotter to the stream. It takes about ten minutes and needs nothing but the application itself.

1. Start the application

Launch NMEA Simulator X. The window opens with the default profile: a vessel off Athens, every standard sentence enabled and one TCP server output on port 10110.

The window has four areas:

  • The dashboard in the centre opens with a compass rose (heading, course and bearing to a destination) and a wind dial, next to the position, time and GNSS status. Below them, digital tiles show heading, speeds, depth, water temperature, altitude and wind.
  • The Map panel on the left shows the vessel on an OpenStreetMap chart. Tiles are downloaded the first time an area is shown and kept on disk, so the map also works offline afterwards.
  • The Console panel at the bottom lists every sentence as it is sent.
  • The Outputs panel on the right lists each configured output with its state, the number of connected clients and the sentences and bytes sent.
  • The toolbar holds the profile and simulation actions.

Panels can be dragged to another edge, floated or closed from the View menu. The layout is remembered the next time you start.

2. Start the simulation

Press Start in the toolbar or press F5. The light in the status bar turns green and reads RUNNING, the console starts scrolling and the Outputs panel shows the TCP server as open.

Type RMC in the console filter to show only the recommended minimum sentence. Tick Pause in the console to freeze the view while the simulation keeps running; untick it to catch up.

3. Take the helm

Click anywhere on the dashboard so the window has keyboard focus, then:

Key Effect
Up / Down Speed over ground plus or minus 0.1 kn
Shift+Up / Shift+Down Speed over ground plus or minus 1 kn
Left / Right Heading minus or plus 1 degree
Shift+Left / Shift+Right Heading minus or plus 10 degrees

Every nudge pins the value: the Override box of that tile becomes ticked and the value stops drifting. Untick the box to let it drift again.

Now enable Steering mode in the toolbar. The arrow keys move the rudder instead of the heading, and the vessel turns at a rate proportional to the rudder angle, as a real hull would. Watch the Rate of turn tile.

4. Override an instrument

Tick Override on the Depth tile and type 4.5. The next DPT and DBT sentences in the console carry the new depth. Untick Fix on the GNSS tile: RMC and GLL switch to their void form and GGA reports quality 0, exactly as a receiver that lost its fix would.

5. Move the vessel on the map

Scroll the mouse wheel over the map to zoom in on the Saronic Gulf, then double-click a spot of open water. The vessel jumps there, the track starts afresh and the sentences carry the new position. Drag the map to look around; the word free view appears because the map no longer follows the vessel. Press Home, or choose View → Follow vessel on the map, to lock onto the vessel again.

Hold Shift and click a spot further along the coast: a magenta diamond marks it as the destination, the Destination tile shows the bearing and distance, and the console starts listing APB, RMB and XTE sentences that an autopilot display would follow. Simulation → Clear destination removes it again.

6. Connect a chart plotter

Any application that accepts NMEA 0183 over TCP can read the stream. With OpenCPN on the same machine:

  1. Open Options → Connections → Add Connection.
  2. Choose Network, protocol TCP, address 127.0.0.1, port 10110.
  3. Apply. The own-ship symbol appears off Piraeus and moves with your keyboard input.

To check the stream without a plotter, on Linux or macOS run:

nc 127.0.0.1 10110

7. Change the setup

Open File → Settings.... On the Simulation tab move the vessel by typing a new latitude and longitude, on the Sentences tab untick GSV to silence the satellite list, and on the Outputs tab add a UDP output in Broadcast mode on port 10110 so every device on your network receives the stream. Press OK: the simulation restarts with the new configuration.

8. Save your setup

Choose File → Save profile as... and store the profile as first-voyage.json. The file holds the seed values, the sentence schedule and the outputs, and can be run headless later with nmeasim run --profile first-voyage.json. The application reopens the last profile on the next launch.

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