Signal K

Signal K is free software that gathers a boat's instrument data (GPS, compass, depth, wind, AIS) from its NMEA 0183 and NMEA 2000 networks and shares it over the boat's WiFi. It often runs on a Raspberry Pi (OpenPlotter, Bareboat Necessities), or on a Victron Cerbo GX. If your boat has a Signal K server, Pelorus Nav can take its position from the boat's own GPS instead of the phone's or tablet's.

Pelorus Nav uses the server's position, course and speed over ground, and heading. If the boat has only a magnetic compass, its heading is converted to true, using the magnetic variation from the server or else the variation printed on the chart for your position.

Android and iOS apps only

Signal K servers on boats almost always use a plain, unencrypted connection, and web browsers won't make one from a secure web page like pelorus-nav.com. Use the Android or iOS app with Signal K; the web version can only connect to a server set up for secure (wss://) connections.

Connecting

1. Join the boat's WiFi network, the one the Signal K server is on.
2. In Settings → Navigation, set GPS source to Signal K.
3. In Signal K server, type the server's address and press Enter (or tap outside the box).

The address is whatever you'd use to open the server's web page: an IP address such as 192.168.1.50, or a name such as openplotter.local. Add the port after a colon if it isn't the usual 3000: 192.168.1.50:3300. You can also paste the address of the server's admin page straight from a browser; Pelorus Nav works out the rest.

While you're typing, the line under the box shows the full address it will connect to when you press Enter. Once saved, a status line shows how the connection is going:

• ✓ Connected, receiving position: all good.

• ⟳ Connecting…: trying for the first few seconds.

• ✕ No network — join the boat's WiFi: WiFi is off, or the phone has no network connection at all.

• ✕ Can't reach the server: the app checks why, and says so:

  • Connection refused — check the port: something is at that address, but no Signal K server on that port.
  • Server name not found — check the address: the name (like openplotter.local) doesn't lead anywhere on this network.
  • Nothing answers at that address — check it, and the WiFi: no device has that address, or it's not on your network.
  • Blocked — allow Local Network for Pelorus in iOS Settings (iPhone and iPad).
  • Server found, but its data stream won't connect: the server answers, but refuses the data connection; check its security settings (below).

  Pelorus Nav keeps retrying on its own, so it reconnects once the problem is fixed. See also When it won't connect.

• ⚠ Connected, but the server has no position: the server is running but nothing is sending it a GPS position. See the server details below.

• ⚠ Connected, but no data is arriving: the server isn't sending anything at all.

On iPhone and iPad, the first connection asks for permission to find devices on your local network. Allow it; if you declined, turn Local Network on for Pelorus Nav in the iOS Settings app.

When it won't connect

The phone or tablet must be on the same network as the server, which on a boat almost always means the boat's WiFi. The server doesn't need the internet, but the phone can't reach it any other way. Check:

• WiFi is on. Airplane mode turns WiFi off, but you can turn WiFi back on while staying in airplane mode, and Signal K then works.
• You're on the boat's WiFi, not the marina's or a phone hotspot. Mobile data can't reach a server on the boat.
• The address and port match what you'd use to open the server's web page in a browser on the same phone. If the browser can't open it either, the problem is the network or the server, not Pelorus Nav.
• The server is running. Its web page shows whether it's receiving data from the boat's instruments.
• iPhone and iPad: Pelorus Nav is allowed on the local network (see above).

Android and WiFi without internet

A boat's WiFi usually has no internet connection, and Android may quietly switch to mobile data because of it, dropping the connection to the server. When Android says the network has no internet access, choose to stay connected. On Samsung phones, also turn off Switch to mobile data (Settings → Connections → Wi-Fi → ⋮ → Intelligent Wi-Fi). iOS shows "No Internet Connection" under the network's name but stays connected.

After a problem is fixed, Pelorus Nav reconnects within about half a minute; Reconnect in Server details tries straight away.

Servers with security turned on

Pelorus Nav doesn't log in to the server. If the server has security turned on, enable its Allow Readonly Access setting (in the server's admin page, under Security) so Pelorus Nav can read the data.

Server details

Settings → Navigation → Server details opens a live view of what the server is sending. It's useful when something isn't working, and interesting when it is.

• Server: the server software and version, the boat's name and MMSI if the server knows them, the address, the connection, and how many messages a second are arriving. If the link has dropped and come back, it says how many times.
• Used by Pelorus: the position, course, speed and heading, each with its value, how many seconds old it is, and which instrument it came from (for example nmea0183.GP for a GPS on NMEA 0183, or n2k.115 for a device on NMEA 2000). A green dot means fresh, amber means it hasn't updated for a while, and red means it has stopped or isn't sent at all. Heading is optional; without it, the boat symbol points along your course.
• GPS quality: the fix type, satellites used, HDOP (how good the satellite geometry is) and satellites in view, if the boat's GPS reports them.
• All data from this server: every value the server has, with its age and source, and how many other vessels it has heard on AIS. Values are shown as the server sends them, in metric units: depths in meters, speeds in meters per second, angles in radians.

Pelorus Nav doesn't yet show depth, wind or AIS targets from Signal K on the chart. The full list shows what your server offers.

Two sources for the same thing

If the source shown for the position isn't the GPS you expected, the boat may have two GPS receivers, and the server is choosing between them. The server's own settings control which source it prefers.

Reporting a problem

Signal K support is new, and every boat's setup is different. If it doesn't work for you, or works in a surprising way, please send a report from Info → Report a Bug. The report includes the connection history and a summary of what the server was sending, which is usually enough to tell what went wrong.