Binnacle Chartplotter

A WebGL chartplotter for Signal K.

It has not been field-tested at any scale. It has been developed and verified against a single Signal K server, never across a fleet or a range of real-world boats, hardware, and conditions. It is also not certified for safety-of-life navigation. Always carry redundant means of navigation, cross-check against your primary instruments, and treat every display as advisory.

What's new in 0.16.0

This release hardens chart imports, provider data, navigation state, and asynchronous map lifecycle handling.

• Private chart URLs. Every query-bearing URL stays device-only by default, query values are redacted in displays and errors, and sending the complete URL to Signal K requires an explicit choice.
• Resilient chart loading. Chart discovery uses signalk-chart-sources 0.4.0, signed PMTiles URLs work without losing their queries, canceled imports stop promptly, and stale same-id overlays cannot replace the user's latest action.
• Bounded provider data. Signal K history and weather, Open-Meteo, RainViewer, marine radar, NOAA CO-OPS, GPX, chart metadata, profiles, symbols, and companion responses are validated and bounded before use.
• Safer long-running sessions. Server chart writes are ordered, radar polling stops on teardown, blocked IndexedDB opens cannot leak connections, and track recording survives RTC or NTP rollback without joining separate segments.
• Stronger release gates. WebKit functional coverage, direct alarm tests, CodeQL, current Svelte and Vite tooling, and stricter package validation now protect the published build.

See the changelog and design system for the full details.

What it does

Signal K is an open marine data standard that streams a boat's navigation, environment, and AIS data over a single API. Binnacle displays that data: a GPU-rendered, offline-capable chartplotter that runs in a browser and is served by the boat's Signal K server.

It is built for low-bandwidth, offline use on modest hardware. It has night-readable themes, computes collision and course data on the client when no server provider supplies them, and caches viewed areas so they keep rendering without a connection. It runs on the same Raspberry Pi that hosts the Signal K server.

Features

Binnacle ships its full feature set as a Signal K webapp:

• Charts and layers: a GPU vector base map, server charts, five streaming bathymetry and ENC sources (NOAA ENC, BlueTopo, and EMODnet each add a nested survey-quality facet; GEBCO is global base bathymetry; Seascape adds globally merged depth shading, hillshade, contours, and soundings), and your own PMTiles charts added by URL or served from the server's charts folder. The Charts tab selects chart sources and opens source details; the Overlays tab controls visibility, opacity, and stacking for marks, routes, weather-adjacent data, and other map overlays. A 24 hour track history layer draws the server-recorded past day under the live track.
• Offline charts: with the optional Chart Locker plugin, draw and save the chart area needed for a passage, choose overview, coastal, or harbor detail, review the estimated download and available storage, and watch visible tile, byte, and error progress. Saved-area cards show coverage, included charts, detail, size, update date, and readiness, with actions to show the area on the chart, download it again, or reuse its settings for an adjusted copy. The same landing page manages automatic caching around the boat, installed chart names and file health, and storage. Without Chart Locker, the menu entry stays visible and explains how to add it.
• Overlays: free, key-free OpenSeaMap seamarks, marine protected areas, maritime boundaries, and NASA GIBS ocean conditions (sea-surface temperature and sea ice), each with its source attribution.
• Marine radar: an optional live radar picture from the Signal K Radar API, rendered over the chart with range rings, a heading line, strict night-red colors, confirmed transmit, immediate standby, direct overlay settings, and the tuning controls reported by the radar. Provider, stream, stale-data, access, and renderer failures remain distinct so an old picture is never presented as live. See Marine radar.
• Routing: draw and save routes as Signal K resources, or tap Go to here (long-press or right-click the chart) to navigate straight to a point. Follow a route with a nav strip (cross-track, distance, bearing, velocity made good, and time to go) over the v2 Course API, with an arrival alarm and extent-aware skip-waypoint controls. A plan speed turns the route into a passage plan with per-waypoint and whole-route arrival times. Routes import and export as GPX to move between Binnacle and other chartplotters and MFDs, and saving an active route refreshes the server's Course API without dropping the current route list during a transient read failure.
• Profiles: keep named helm setups containing the theme, chart and weather layers, collision thresholds, track and planning settings, unit fallback, toolbar pins, instrument selection, and preferred anchor radius. Changes to the active profile save automatically. Profiles, defaults, and edits sync through Signal K when you are logged in, while each browser keeps its own active choice and chart view. Concurrent edits merge by setting instead of replacing the whole profile. Signal K 2.23.0 and later provide the strongest atomic cross-station revision protection, while older servers retain local saves and best-effort synchronization. See Profiles and settings.
• Instruments: tap the Instruments pill and the chart slides left for a gauge dock (SOG, heading, depth, apparent wind, and more from a curated catalog you pick and reorder); on a phone the tiles take the full screen, KIP-style. Values color by your server's configured meta.zones alarm bands, and selections ride profiles. Customize discovers the live Signal K model and, when a history provider is installed, equipment recorded during the preceding year. Previously recorded readings remain clearly marked and never replace live values. Dynamic options name both the reading and source, while a catalog-level fallback keeps future repeated labels distinct. Open KIP launches the installed KIP webapp; when KIP is absent, the item stays visible but unavailable and explains how to add it.
• Weather: a zoom-capped mini-map with animated WebGL wind, pressure isobars, waves, precipitation, cloud, and radar, plus time-aware point readouts, marine forecasts, source and age labels, deterministic risk cues, and official warnings when a Signal K weather provider supplies them. Open-Meteo provides the key-free fallback, including wind waves, swell, currents, and sea surface temperature, while cached forecasts remain available offline with explicit stale labeling.
• Tides: the nearest tide station's next high and low with a 48-hour curve and the nearest tidal-current station's next flood or ebb. NOAA CO-OPS covers US waters out of the box; the signalk-tides plugin extends coverage worldwide when the server runs it.
• Lookout: a collision watch with CPA and TCPA, chart-highlight rings, an audible alarm, and a published Signal K notification, plus a sortable AIS target list (by range, CPA, or name) with live range and bearing, tap-to-locate, and faded target trails from the tracks plugin. An Alarms panel collects every active alert on the boat (engine, autopilot, any plugin) with one-tap Silence and Acknowledge that propagate to every station.
• Anchor watch: drop the anchor at the boat, set the swing radius (or capture it from the live distance), and get a drag alarm that latches until acknowledged. It drives the signalk-anchoralarm-plugin when installed (so the alarm keeps running with the browser closed) and falls back to a fully in-browser watch when it is not, with a draggable drop-point marker on the chart.
• Man overboard: an always-visible MOB button in the top bar with a confirm pop-out. Confirming marks the spot, publishes the boat-wide Signal K alarm, and raises a recovery strip with live bearing, range, and elapsed time, plus an opt-in Steer to MOB handoff to the course system. An MOB raised by another station shows here too.
• Measure: tap points on the chart for rhumb-line leg range, true bearing, and a running total. The active strip guides each next tap, Undo and Clear keep the tool active, and Done removes its temporary session-only points.
• Tracks: record, pause, save, show, and export segmented voyage tracks as GeoJSON. GPS gaps never become invented route legs. Save the latest continuous segment as a reusable route, or confirm a retrace to navigate home along it. The panel explains persistence, access, loading, and refresh failures instead of silently losing state. The active trail survives reloads in IndexedDB, while completed tracks live in Signal K resources and can be shared with other clients.
• Waypoints: drop one from a long press, see it as a named marker, and locate, navigate to, rename, or delete it from the Waypoints panel. Loading and failures stay explicit, accepted writes survive refresh failures, and navigation requires confirmation. Marks live in the server's waypoint resources, so they interoperate with other Signal K clients.
• Trends: depth, apparent wind, barometric pressure, and speed over the last 24 hours as themed graphs from the server's v2 History API, or live session sampling without a history provider.
• Find places and points of interest: search the notes in the current chart view by name, category, or provider; sort them by name, category, distance, or true bearing; preview and select a result on the chart; and open its structured detail. Loading, zoom-limit, cached-offline, empty, and provider-error states remain distinct. Custom chart symbols are supported through the signalk-symbol-manager plugin. See Find places.
• Your units: every readout follows the server's imperial-or-metric unit preference; knots, nautical miles, and bearings stay nautical.
• Themes: day, dusk, and night-red, with true red on black for a dark-adapted watch.

See the changelog for the full list.

Architecture

Binnacle is built on a current web stack and engineered to run on modest helm hardware:

• Front end. Svelte 5 with runes, Vite, and TypeScript, linted and formatted with Biome. The code is organized as cohesive, single-responsibility slices under a strict Feature-Sliced Design, with the import boundaries enforced by the build through a dependency-cruiser gate, a modular stylesheet assembled one concern per file, and shared UI primitives and helpers, so a new feature drops in against stable interfaces rather than by surgery on the core.
• GPU rendering. MapLibre GL JS draws the vector base map and chart layers on the GPU. The own vessel and every AIS target render as GPU symbol layers, and wind draws as a WebGL particle field advected through the forecast on the graphics card.
• Off-main-thread real-time pipeline. A dedicated Web Worker hosts the Signal K WebSocket client; deltas are coalesced into frame-rate batches on a worker timer and fed into a path-keyed reactive store, so a busy AIS anchorage updates the readouts without stalling the chart render, and data and alarms keep flowing while the tab is in the background. A failed stream can recreate the worker, reconnect, and replay subscriptions without reloading the chartplotter.
• Minimal network and render work. Binnacle subscribes to exactly what it draws, keeps everything in SI internally, and converts only at the display edge.
• Offline caching. Self-hosted fonts and assets (no CDN for app code). PMTiles chart areas are cached as blocks in IndexedDB at the protocol layer, so they work offline even over plain http; tides, notes, weather, and the vessel conditions persist the same way. Over https a service worker additionally caches the base map, plugin chart tiles, supported online overlays, and predictions. With Chart Locker installed, server-side saved areas, automatic caching, shared tile storage, and installed PMTiles files add a boat-wide offline layer that is independent of one browser's cache.

Requirements

• Signal K server 2.x.
• Node.js >= 22.18 (for building from source).
• A browser on the helm display, tablet, or phone.
• Optional: signalk-chart-locker for server-managed saved areas, automatic caching, shared storage, and installed PMTiles chart management.
• Optional: a Signal K Radar API provider, such as Mayara, for the marine radar overlay and controls.

Installation

Binnacle is a Signal K webapp. The production build ships inside the package, so there is nothing to build.

From the App Store (recommended). In the Signal K admin UI, open Apps and Plugins, then Store, search for Binnacle, and install. Open it from the Webapps list.

With npm. Install into the server's home directory and restart Signal K:

cd ~/.signalk
npm install signalk-binnacle

From source. See Development below.

Optional offline-chart management. Install Chart Locker (signalk-chart-locker) from the Signal K App Store, then start the plugin. Binnacle detects it automatically. A secured server may require you to sign in to Signal K as an administrator before downloads and chart-name edits are enabled. This is separate from approving Binnacle's ordinary read/write access request. Chart Locker management calls use the browser's Signal K administrator session, not Binnacle's device token. Binnacle checks Signal K's live login status before suggesting sign-in, so a Chart Locker permission failure does not mislabel an authenticated administrator as signed out.

Optional marine radar. Run or configure a provider that exposes the standard Signal K Radar API at /signalk/v2/api/vessels/self/radars. Mayara is the reference provider. Binnacle discovers radars, hydrates /controls, listens for radars.*.controls.* Signal K deltas, and opens the selected radar's reported spoke stream. Read access is sufficient for the picture; transmit, standby, and tuning writes require read-write approval. See Marine radar setup and behavior.

Usage

Open Binnacle from the Webapps list in the Signal K admin UI, or go straight to http://your-sk-server:3000/signalk-binnacle/. It opens on the chart, centered on your boat.

A few interactions cover most of the helm:

When installed as a PWA on a touch device, Binnacle automatically reserves bottom clearance for Android navigation and tablet taskbars. The status strip and mobile app-menu sheet also follow reported bottom and landscape side safe areas, so their helm controls remain reachable when system chrome overlays the app window.

The Profiles panel includes Forget credentials and Erase all local data for a shared or retired display. These actions affect only Binnacle data in the current browser. They do not delete Signal K routes, waypoints, tracks, profiles, Chart Locker data, administrator sessions, or server-side device authorization. Synced profiles return after the browser signs in and syncs again. Profiles and changes that have not synced are permanently lost. Full erasure is blocked while MOB, anchor watch, navigation, route editing, measurement, or an unsaved recorded track is active.

Network privacy

Binnacle gets boat data from your Signal K server and loads its vector base map from OpenFreeMap when the chart opens. When their chart or overlay layers are visible, the browser can also request tiles from OpenSeaMap, NASA GIBS, Open Water Seascape, GEBCO, EMODnet, and NOAA services for ENC, BlueTopo, and marine protected areas. The maritime-boundaries overlay requests VLIZ Marine Regions.

Opening weather or enabling its optional layers can contact Open-Meteo and RainViewer. Opening tides can contact NOAA CO-OPS when a Signal K tide provider is unavailable. These services can observe your public network address and the requested tile, map area, or forecast coordinates. Optional marine, weather, and tide requests are made only when the corresponding layer or feature is used, and cached results remain usable when a provider is unavailable.

User-added URL charts are fetched by the browser. Binnacle rejects URLs with embedded usernames or passwords, removes URL fragments, redacts every query value in displays and errors, and keeps every query-bearing URL on this device unless you explicitly choose to share the complete URL with the Signal K server. Use HTTPS for Signal K so device credentials and boat data are encrypted on the local network.

• Open the context menu. Long-press the chart on a touch screen, right-click with a mouse, or focus the chart and use the Context Menu key or Shift+F10. Drop a waypoint, choose Go to here to navigate straight to that point, or start a route or measurement.
• Measure a chart leg. Open Measure, tap a start and destination, then read the latest rhumb range, true bearing, and total in the strip. Use Done when finished.
• Manage charts and overlays. Open Charts to select chart sources or inspect their details. Switch to Overlays to toggle overlays, change opacity, and drag rows to reorder their stack.
• Prepare offline charts. Open Offline charts, choose Save a chart area, draw over the passage, review the included charts and detail, and start the download. Confirm the saved area's status and update date before relying on it away from coverage.
• Switch themes. Cycle the day, dusk, and night-red themes from the theme control. Night-red is pure red on true black for a dark-adapted watch.
• Mark a man overboard. Tap the always-visible MOB button in the top bar and confirm to mark the spot, raise the boat-wide alarm, and start the recovery strip.

For caching behavior, storage, and HTTPS requirements, see Offline charts, Chart Locker, and SSL below.

For behavior, availability, recovery states, and safety rules for every menu action, see Menu items. Detailed guides also cover Tracks, Waypoints, Find places, Measure, and Marine radar. Offline preparation and administrator-session troubleshooting are covered in Offline charts.

Offline charts, Chart Locker, and SSL (optional)

Chart Locker is optional, but it is the recommended way to prepare a passage rather than depending only on charts viewed previously in one browser. Install signalk-chart-locker from the Signal K App Store, then open Offline charts in Binnacle. If the plugin cannot be reached, that menu item stays visible but unavailable and explains whether to install, start, or sign in to Signal K as an administrator. When administrator access is required, the header status opens that sign-in directly. The sign-in flow stays in the PWA window and redirects back to the current Binnacle route. If Signal K already reports an administrator session but Chart Locker refuses it, Binnacle reports an access error and offers a retry instead of asking the administrator to sign in again.

For the full setup, access, troubleshooting, download, and storage workflow, see Offline charts.

The Offline charts landing page has four jobs:

1. Saved areas. Choose Save a chart area, draw a rectangle on the chart, review the smart default chart selection, pick Overview, Coastal, or Harbor detail, check the estimated download and free space, name it, and start the download. On a phone, the panel collapses while drawing so the chart owns the gesture. A saved-area card is ready only when it says Saved, works offline. Accepted downloads recover by area identifier if their immediate job response is lost, and a temporary status failure offers Retry status without starting a duplicate download. If a saved definition references a removed chart source, Binnacle preserves the existing cached coverage, labels the missing source, and directs the user to adjust a copy before downloading again.
2. Automatic caching. Optionally keep selected charts cached around the moving boat. This is a rolling nearby cache, not a substitute for saving and verifying the full planned passage. Settings follow Chart Locker's limits for 64 sources, zoom 0 through 24, distances up to 100 km, and update intervals from one minute through 24 hours.
3. Installed charts. Rename installed PMTiles charts, edit their descriptions, inspect bounds, zoom range, and scale, refresh the file list, and see actionable errors for invalid files. Add, replace, or remove archives in the Chart Locker chart folder on the Signal K server.
4. Storage. Review saved-area, recently viewed, and automatic-caching usage, choose when recently viewed charts clear, and clear only that expendable cache without deleting saved areas.

The header's Offline status reports the cache amount or a service problem. It does not certify that a particular passage is complete. Before leaving coverage, open Offline charts and verify the intended area's coverage, included charts, Saved, works offline status, and update date.

SSL is not required. Binnacle runs fully over plain HTTP, which is how the Signal K server serves it by default: the chart, AIS, weather, points of interest, tracks, and the Lookout alarms all work without it.

Much of the offline caching works without SSL. PMTiles chart areas, the weather forecast, tides, chart notes, and the vessel conditions are cached in IndexedDB, which is not secure-context gated, so even over plain HTTP a reload replays the last data and previously viewed PMTiles charts keep rendering offline. What SSL adds is the service-worker layer: browsers expose the service worker and cache-storage APIs only in a secure context (HTTPS or http://localhost), so caching the base map, plugin-served chart tiles, and the streaming overlays activates only when the server is reached over HTTPS. Over plain HTTP those degrade cleanly to online-only with no loss of live function.

Chart Locker's server-side downloads and cache work independently of the browser service worker, so they do not require HTTPS. HTTPS is still valuable because it enables Binnacle's additional browser-side service-worker cache for the base map, plugin chart tiles, and streaming overlays.

There are two good ways to add HTTPS to Signal K:

• The signalk-ssl plugin (source), which generates a local certificate authority, issues the server certificate, and distributes the root to your devices by QR code. It runs its certificate tooling on the shared signalk-container runtime. The Signal K server's built-in SSL settings (Server, then Settings, then SSL) are a bare-bones alternative.
• Tailscale, which adds remote access and publicly trusted certificates (no trust-store step at all) in one move. See Accessing Signal K remotely with Tailscale for a quick start, including a clean signalk.<tailnet>.ts.net service name.

One more step is required, and it is easy to miss: your browser has to trust that certificate, not just reach it. A self-signed certificate, including one the signalk-ssl plugin generates, is not trusted by default, and browsers refuse to register a service worker from an origin whose certificate they do not trust, even after you click through the page's certificate warning. So if you only accept the one-time warning, the page loads but offline caching never activates, and the console shows a message like "service worker registration failed: an SSL certificate error occurred." To fix it, install the certificate authority's root (the QR code or .pem the plugin gives you) into your browser or operating system trust store and mark it trusted, then reload over HTTPS. Once the certificate is trusted, the service worker registers and the base map and chart tiles cache for offline use.

Development

Development targets Node 22.18 or newer and npm 11.6 or newer. The recommended npm version is 11.18.0. .node-version and packageManager record the project defaults, while devEngines enforces the supported minimums. All tools use repository-local dependencies.

git clone https://github.com/NearlCrews/signalk-binnacle.git
cd signalk-binnacle
npm install        # install dependencies
npm run hooks      # install the git pre-commit and pre-push gates (run once)
npm run dev        # Vite dev server
npm run check      # type-check application, tooling, and browser tests
npm run lint       # code, Svelte, Markdown, and spelling checks
npm run format     # Biome format (write)
npm run ci:biome   # format, lint, and import-order verification
npm run cruise     # dependency-cruiser boundary check
npm run deadcode   # unused files, dependencies, and public exports
npm test           # Vitest unit tests
npm run test:coverage # unit tests with the enforced coverage floor
npm run build      # production build into public/
npm run size       # compressed production bundle budgets
npm run verify     # complete non-browser local and CI gate
npm run test:e2e   # Chromium browser checks against an existing build
npm run test:e2e:cross-browser # Chromium and WebKit UI checks; CI runs this gate
npm run verify:release # full gate, cross-browser E2E, package checks, and runtime audit

After npm run hooks, git runs verify:commit before each commit and verify:browser before each push. The hooks live in .githooks/ and are opt-in via core.hooksPath, never a package lifecycle script. The E2E commands consume the existing public/ build; use the :with-build variants when running them directly from a tree without a current build.

Maintainers preparing a version should follow the release checklist. Preparation does not authorize a tag, GitHub release, or npm publication.

To run a local build inside your own Signal K server, link it into the server's module directory and add it to the server config so it loads:

ln -sfn "$(pwd)" ~/.signalk/node_modules/signalk-binnacle

{
  "dependencies": {
    "signalk-binnacle": "file:../path/to/signalk-binnacle"
  }
}

Restart Signal K, then open http://your-sk-server:3000/signalk-binnacle/ in a browser.

License

Apache-2.0. See LICENSE for the full text. The software is provided "AS IS", without warranty of any kind. It has not been field-tested at scale and is not certified for navigation. Treat all on-screen information as advisory, and always carry independent means of position-fixing.

Acknowledgments

Binnacle is written and maintained by Nearl Crews. It stands on open data and open source:

• Signal K Project for the open marine data standard.
• MapLibre GL JS for the GPU map renderer, and OpenFreeMap for the vector base map, built from OpenStreetMap data under the Open Database License.
• Open-Meteo for atmospheric and marine forecast grids, and RainViewer for precipitation radar.
• NOAA for the ENC chart, BlueTopo bathymetry, the MPA Inventory, and the CO-OPS tide and current predictions; EMODnet for European bathymetry and protected areas; GEBCO for global bathymetry; Open Water Software for Seascape, merging GEBCO, EMODnet, NOAA CUDEM, and other regional sources into worldwide depth shading, hillshade, contours, and soundings; NASA EOSDIS GIBS for the ocean-conditions imagery; OpenSeaMap for the seamark overlay; and the Flanders Marine Institute (VLIZ) Marine Regions service for the maritime boundaries.

Custom chart symbols come from signalk-symbol-manager by Joel Kozikowski, who also contributed the symbol rendering Binnacle uses in #6.

Binnacle pairs well with sibling plugins such as signalk-crows-nest, which supplies the points of interest it renders, and works with any Signal K weather provider, such as signalk-virtual-weather-sensors.

Support

Find this project useful? You can support its continued development by buying me a coffee.

• Report a bug
• Request a feature
• Security issues