NMEA & GPS Setup¶
Bristol Maps can connect to external NMEA devices over your local network for GPS positioning, depth sounder data, water temperature, and AIS vessel tracking.
What is NMEA?¶
NMEA 0183 is a standard protocol used by marine electronics. By connecting Bristol Maps to an NMEA server (such as a Yacht Devices gateway, chart plotter, or other marine electronics), you can:
- Use an external GPS instead of the device’s built-in GPS
- Display water depth from a depth sounder on the navigation banner
- Read water temperature from a temperature sensor
- Receive AIS data from an AIS receiver
- Steer your autopilot along a waypoint or route (see Autopilot)
Connecting to an NMEA Server¶
- Open Settings from the Tools tab
- Scroll to the NMEA Settings section
- Tap + Add NMEA Connection to open the connection form
- Enter the IP Address of your NMEA server (e.g.,
192.168.0.208) - Enter the Port number (e.g.,
1456) - Tap Connect
The connection status will show whether the link is active.
Network Required
Your device must be on the same local network as the NMEA server. This typically means connecting to the same Wi-Fi network or a direct connection.
NMEA Features¶
Depth Sounder¶
When connected to a depth sounder via NMEA, the water depth is displayed on the navigation banner.
| Setting | Description |
|---|---|
| Depth Sounder Offset | Calibration offset for the depth reading (e.g., to account for transducer placement) |
| Depth Data Sharing | Toggle to broadcast depth data to your fleet group |
AIS Sharing¶
Enable AIS Sharing to relay AIS vessel data received from your local AIS receiver to your fleet group via the cloud. Group members will see the same AIS targets on their maps.
See AIS Vessel Tracking for more about AIS features.
NMEA Location Updates¶
Enable NMEA Location Updates to use the external GPS from your NMEA server instead of your device’s built-in GPS. This can provide more accurate positioning if you have a high-quality marine GPS receiver.
Starlink GPS is no longer available
Starlink discontinued the local-network location sharing that Bristol Maps relied on, so the Starlink router can no longer be used as a GPS source and the option has been removed from Settings. Use a device with built-in GPS (a cellular iPad or a Hugerock tablet), the boat’s NMEA GPS as described above, or an external GPS receiver instead. See Picking a device for hardware options.
Supported NMEA Sentences¶
Any talker ID is accepted (e.g. $GPRMC, $GNRMC, $IIDBT). What each app reads:
| Sentence | Data | Mobile (iPhone/iPad/Android) | Desktop |
|---|---|---|---|
| RMC | Position, course and speed (status A only) |
Yes | Yes |
| GGA | Position (fix quality 1 or higher), satellites, HDOP | Yes | Yes |
| GLL | Position (status A only) |
Yes | Yes |
| VTG | Course and speed over ground (true course, magnetic if that is all there is) | Yes | Yes |
| DBT / DBS / DPT | Depth (also Furuno $FUDPT with echo strength) |
Yes | Yes |
| $PSIMSNS | Simrad depth with signal strength | Yes | Yes |
| $PCDIN | NMEA 2000 water depth and engine data from Yacht Devices gateways | Yes | Yes |
| $YDXDR / $YDMDA | Yacht Devices air/water temperature and pressure | Yes | No |
| !AIVDM | AIS vessel tracking (types 1, 3, 5, 18) | Yes | No |
Course and speed from VTG or RMC are paired with the next position. A GPS that sends the same fix as several sentences (for example GGA, RMC and GLL) moves the boat once, not three times.
Bristol Maps’ own GPS sharing server sends GLL + VTG, so another phone, tablet or desktop running Bristol Maps can use it as its GPS.
Desktop AIS and temperature
The desktop app shows AIS targets and water temperature only from a NMEA 2000 RAW feed
(a Yacht Devices gateway in RAW mode or the Bristol N2K Bridge). NMEA 0183 AIS (!AIVDM) and
temperature sentences show as Received (not decoded on desktop) in the device status.