Selma Racing Mode

SelmaRacing Mode

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No race selected

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Boat	SOGkn	VMCkn	DTWnm	ETA	Δ vs menm	5′	15′	Age

Event log

Tacks, mark roundings and alerts will appear here.

Measured now

No position yet

Model	Windkn · Δ	Gustkn · Δ	Dir° · Δ	Score	Updated
No models selected — choose models in Setup → Weather models.

Δ = forecast − measured. Score ranks the selected models against each other by recent agreement with your B&G instruments at this position (wind, gusts, direction). Higher is better — but it reflects skill here, now, not necessarily downstream where you're routing to.

Rolling accuracy · window min

Model	Wind biaskn	RMSEkn	Gust biaskn	Dir bias°	Dir RMSE°	n
No comparison cycles recorded yet.

Bias = mean signed error (a steady offset across all models usually means instrument calibration, not the model). Forecast snapshots stored for future lead-time scoring: 0.

Choose which models to rate, and tune the comparison, in Setup → Weather models.

Corrected leaderboard

Corrected = (elapsed + projected time to finish at current VMC) × ToT. Finished boats use their actual elapsed. Lower is better; ratings in Fleet.

#	Boat	Mark	DTWnm	To finnm	SOGkn	VMCkn	ToT	ETA fin	Corrected

Replay

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Select a race with recorded data.

Boat	SOG	VMC	DTW	Mark

Set up the B&G bridge

The bridge is a small program that listens to your B&G instruments on the boat Wi-Fi and hands the data to this page. It must run on this computer, in a window you keep open while racing. Setup takes about 10 minutes the first time; afterwards it is one double-click.

Install Node.js (once)

Node.js is the free runtime the bridge needs. Open nodejs.org/en/download, choose macOS Installer (.pkg) for the LTS version, open the downloaded file and click Continue until it finishes.

To check it worked: press ⌘ Space, type Terminal, press Enter, then paste this and press Enter. It should print a version like v22.x.x.

node -v
Download the bridge program

Click the button. Your browser saves nmea-to-ws.mjs to your Downloads folder. Leave it there.

⬇ Download nmea-to-ws.mjs
Join the boat network

Connect this Mac to the same Wi-Fi as the B&G plotter: either the plotter's own GoFree-xxxx network (no internet) or your boat router / Starlink if the plotter is joined to it. On the plotter, NMEA 0183 output over Wi-Fi must be switched on (Settings → Network → NMEA 0183 or NMEA over Wi-Fi, wording varies by model).

Plotter address — Noisy Oyster's B&G serves NMEA 0183 over TCP at 192.168.1.98:10110 (pre-filled): port Find it on the plotter under Settings → Network → Info (IP address) and … → NMEA 0183 → TCP (port, usually 10110). Change it only if the plotter's IP differs on this network; clear it if the plotter broadcasts over UDP instead. The commands and the launcher below update as you type.
Start the bridge

In Terminal, paste this line and press Enter:

Within a few seconds you should see [ws] serving on ws://localhost:8787/ and then lines counting incoming data. If macOS asks whether node may accept incoming network connections, click Allow. Keep this Terminal window open — closing it stops the bridge.
Connect this page to the bridge

Click the button below. It selects the local bridge as data source, fills in the address and connects. The status bar at the top should turn to B&G bridge connected within a few seconds, and boats appear in Live once AIS data arrives.
If nothing arrives after a minute

The plotter is probably broadcasting on a different port. Stop the bridge with Ctrl+C in Terminal, then run discovery mode — it listens on all common ports and prints where data shows up:

Look for lines like [udp:2052] from 192.168.x.x. Note the port number, stop with Ctrl+C, and start again with that port:

If discovery shows nothing at all, the Mac is not on the plotter's network or the plotter is not sending NMEA over Wi-Fi — check step 3.

Position wrong by a few miles? Read the [own] lines in Terminal: they list every GPS device heard (e.g. GPRMC, IIGLL) with its raw coordinates and the distance between them. If two disagree, one device has a bad fix — pin the good one by adding --gps-source GP (the two letters after the $) to the start command.
Next time

Only steps 3–5 are needed: join the boat Wi-Fi, paste the start line into Terminal, click "Use the bridge and connect".

Install Node.js (once)

Node.js is the free runtime the bridge needs. Open nodejs.org/en/download, choose Windows Installer (.msi), 64-bit, LTS version. Run it and click Next through all screens with the default options, then Finish.

To check it worked: press the Windows key, type PowerShell, press Enter, paste this and press Enter. It should print a version like v22.x.x. (If it says "not recognized", restart the computer once.)

node -v
Download two files

Both go to your Downloads folder. They must stay in the same folder as each other.

⬇ Download nmea-to-ws.mjs

If the browser warns that a .cmd file "isn't commonly downloaded", choose Keep. It is a plain text file that only starts the bridge; you can open it in Notepad to read it.
Join the boat network

Connect this PC to the same Wi-Fi as the B&G plotter: either the plotter's own GoFree-xxxx network (no internet) or your boat router / Starlink if the plotter is joined to it. On the plotter, NMEA 0183 output over Wi-Fi must be switched on (Settings → Network → NMEA 0183 or NMEA over Wi-Fi, wording varies by model).

Important: when Windows asks whether this network is Public or Private, choose Private (or later: Settings → Network & internet → Wi-Fi → the network → Network profile type → Private). On a Public network Windows silently blocks the data the bridge needs.

Plotter address — Noisy Oyster's B&G serves NMEA 0183 over TCP at 192.168.1.98:10110 (pre-filled): port Find it on the plotter under Settings → Network → Info (IP address) and … → NMEA 0183 → TCP (port, usually 10110). Change it only if the plotter's IP differs on this network; clear it if the plotter broadcasts over UDP instead. The commands and the launcher below update as you type.
Start the bridge

Open the Downloads folder and double-click "Start bridge.cmd". A black window opens. The launcher already dials the plotter at the address from step 3.

First time only: if a blue "Windows protected your PC" box appears, click More info, then Run anyway. If Windows Defender Firewall asks about Node.js, tick both "Private networks" and "Public networks", then Allow access.

The window should show [ws] serving on ws://localhost:8787/ and then lines counting incoming data. Keep this window open — closing it stops the bridge.

Prefer typing it yourself? PowerShell alternative
Connect this page to the bridge

Click the button below. It selects the local bridge as data source, fills in the address and connects. The status bar at the top should turn to B&G bridge connected within a few seconds, and boats appear in Live once AIS data arrives.
If nothing arrives after a minute

Most common cause on Windows: the firewall. Check the network is set to Private (step 3). Second cause: the plotter broadcasts on a different port. Close the bridge window, download and double-click this discovery launcher — it listens on all common ports and prints where data shows up:

Look for lines like [udp:2052] from 192.168.x.x. Note the port number, close that window, then in PowerShell paste (replace 2052 with your port):

If discovery shows nothing at all, the PC is not on the plotter's network, the network is Public, or the plotter is not sending NMEA over Wi-Fi — check step 3.

Position wrong by a few miles? The launcher also writes everything (and every raw NMEA sentence) to selma-racing-bridge-debug-output.log next to the script — send that file for diagnosis. Read the [own] lines in the bridge window: they list every GPS device heard (e.g. GPRMC, IIGLL) with its raw coordinates and the distance between them. If two disagree, one device has a bad fix — pin the good one by adding --gps-source GP (the two letters after the $) to the start line in Start bridge.cmd.
Next time

Only steps 3–5 are needed: join the boat Wi-Fi, double-click "Start bridge.cmd", click "Use the bridge and connect".

This page is served over HTTPS, so the browser only allows a bridge running on the same computer (localhost). Running it on another machine requires opening the app over plain http — see the project's bridge README.