Navigate · Chartplotter
The chart, AIS, tides, and your route — in one place.
I built the chartplotter to be the primary navigation surface on the boat: smooth vector charts, first-class AIS overlaid directly on the chart, harmonic tide predictions at every waypoint, and weather forecast layers you can scrub forward in time. It runs locally first, syncs when online, and never drops data because the satellite link went out.
How it works
Built around how sailors actually navigate.
AIS isn't a sidebar add-on. Tides aren't a separate lookup. Weather isn't a screenshot from a third-party app. They're all layers on the same chart, sourced from the same data pipeline, rendered together.
Vector charts via PMTiles
Charts are stored as PMTiles — a self-contained tile archive that loads fast on the local network, streams from the service worker cache when offline, and doesn't require a tile server to keep running. Med + Atlantic coverage at launch; worldwide tiles in the same format.
First-class AIS ingest
AIS messages come off the NMEA-2000 gateway and flow into the bus as typed, source-tagged events. The chart consumes them directly — every target renders with its course-over-ground vector, name, and closest-point-of-approach distance. No separate AIS widget. No copy-paste from a VHF screen.
Harmonic tide engine
I run a harmonic tide predictor on the boat — not an API call to a third-party service. At each waypoint on your route, the chart shows predicted water level at your estimated arrival time. Approaching Menorca at 18:40 on Thursday? You'll see whether the harbour entrance has the depth you need.
Local-first, IndexedDB-backed
Your route, your track history, your waypoints — all in IndexedDB on the hub. The sync engine mirrors them to the cloud when the connection is up. If you're in the middle of the Mediterranean with no satellite link for six hours, the chart keeps working exactly as it did when you were alongside.
Polars-aware routing
Every route validates against your boat's polars — the performance curve that describes what speed you'll make at a given wind angle. The default polar comes with the boat profile; you can override it per route. The chart shows you when a leg is going to be slow upwind, not just straight-line distance.
Weather overlays, scrubable
Wind barbs, swell arrows, current vectors — from the same multi-model forecast the Weather app uses. Scrub forward to see conditions at the time you'll arrive at each waypoint. Decide in the planning phase, not at the waypoint.
Real scenario
Approaching the marina at 5 knots.
What the chartplotter actually does in the last hour of a passage, with specific numbers.
The final approach
You're 4nm out, making 5.1 knots over the ground, heading 280° magnetic. The chart shows two AIS targets: a motor yacht crossing your bow at 12 knots, closest-point-of-approach 0.4nm in 6 minutes; a fishing vessel anchored 1.2nm to the north. Both are labelled, both have course-over-ground vectors. You don't need to look at the radar and translate.
At the marina waypoint, the tide prediction shows a 0.9m rise on a chart datum of 1.1m — the harbour entrance you need 1.8m to clear. The chart turns the waypoint amber. You see it. You adjust your arrival time by 40 minutes and the waypoint goes back to white.
The SVG schematic
Where it's going
What's built now and what comes next.
The core chart, AIS, and tide engine are in. Here's the sequence of what follows.
Core chartplotter
PMTiles vector charts for the Mediterranean and North Atlantic. AIS overlay sourced from the bus. Harmonic tide predictions at waypoints. Route entry, polar validation, and track logging to IndexedDB.
Passage integration
Passage planning pushes the validated route directly into the chartplotter. Route progress is shared back to the cockpit in real time. Waypoint notes and harbour pilot information appear inline on the chart as you approach.
AI-assisted navigation
The AI agent host gets read access to your chart state. Ask "is there any traffic on the approach to Port Mahon in the next two hours?" and get an answer drawn from the live AIS feed, without leaving the chart.
See it running in the demo.
The demo lets you explore the chartplotter interface — chart pan and zoom, AIS targets, route drawing — without connecting any hardware. Or go back to the platform overview to see how the chartplotter fits with the rest of the stack.