Offline marine charts

Charts that work where the signal doesn't.

NautiNerd draws official nautical charts on your phone, with its own chart engine. Plan a route, follow it with cross-track error and ETA, log your passage and keep an anchor watch that wakes you when the boat drags. No account, no signal needed at sea.

Open the web app Android & iPhone

Free official charts where governments publish them: US coasts and rivers, the inland waterways of eleven European countries, Brazil and Norway. Chart files (S-57, BSB/KAP) from any hydrographic office, and an unofficial sea map for everywhere else.

Official S-57 ENCs
Drawn on your device
Works offline
Day, dusk and night
Account optional, no ads, no profiling

Get charts

Frame the water you sail. Download. Done.

Move the map to your cruising ground and NautiNerd shows which official charts cover it, from overview to harbour detail, with their size: NOAA and the US Army Corps of Engineers, the inland waterway authorities from the Rhine to the Danube delta, Brazil's Navy and Norway's Kartverket. One tap downloads them for good; when corrections are published, the app tells you and updates them.

Choosing an area: NOAA chart coverage over Monterey Bay with a download button

Anchor watch

Sleep. NautiNerd keeps watch.

Drop anchor, set the swinging circle and put the phone away. If the boat leaves the circle, the phone wakes up and sounds a loud alarm, even in silent mode and with the screen off. The watch survives restarts and shows how far you have swung.

Anchor alarm: the boat is 76 m from the anchor, beyond the 40 m swinging circle

Tap anything

What is that buoy? Ask the chart.

Tap a mark, a light or a wreck and read it in plain words: its light characteristic, its colours, the charted depth around it, how far it is from you. Hazards come first.

Information about the Alcatraz lighted bell buoy AZ

Sea map

No official charts? Sail with the sea map.

In much of the world official charts are encrypted and sold. NautiNerd saves a sea map for any area instead: seamarks from OpenStreetMap (and, in Finland, Norway and the Netherlands, the authorities' own open buoy, light and depth data) drawn with proper chart symbols, depth relief and a clean background map, ready offline. It is clearly marked as unofficial, and an official chart always takes over where you have one.

Sea map of Lipari harbour with marinas, lights and seamarks from OpenStreetMap

AIS and instruments

See the ferry before it sees you.

Connect NautiNerd to your boat's NMEA Wi-Fi gateway and the ships around you appear on the chart, with their course and a warning when one is set to pass too close. Depth and wind from your own instruments sit right under your speed and course.

A ferry on a collision course shown with a red course vector and a collision warning

Routes and navigation

Tap out a route, drag its points, follow it. Distance and bearing to the next mark, cross-track error and ETA, with automatic leg switching.

Logbook

Record your passage in the background, see distance, time and speed, and share tracks as GPX.

Your safety depths

Set your safety contour and depth; shallow water and isolated dangers are shaded and marked the way professional chart systems do it.

Night mode that keeps your night vision

Day, dusk and night palettes for the chart and the app, with no bright whites in the cockpit at night.

Weather like the pros

Wind, gusts, pressure, rain, waves, swell and currents over the chart, animated, from ECMWF, GFS, ICON, AROME and more. Compare the models at any point and save the forecast for your passage.

Tides and tidal streams

Heights, high and low water and stream rates for nearly 9,000 stations worldwide, computed on your phone, offline.

Cruising guide

Over 120,000 marinas, anchorages, moorings, fuel docks, slipways and boatyards on the chart, with VHF channels and contacts, and reviews from other sailors.

Your modules

Add what you need to the dock: weather, tides, the guide, boat instruments and AIS. Leave out what you don't.

Private by design

Charts, positions, tracks and routes stay on your device. An account is optional and only syncs your logbook between your devices. Usage is counted anonymously and without cookies; positions are never sent.

Under the hood

Our own chart engine. Checked, not hoped.

NautiNerd reads official electronic navigational charts (IHO S-57) directly and draws them by the S-52 display rules with an engine written from scratch in Rust, running on your device.

43,000: chart objects decoded identically to GDAL, an independent decoder, across 32 NOAA charts
12: reference scenes compared side by side with NOAA's official rendering, same settings
0: servers involved in drawing your chart: decoding and rendering happen on the device

Get NautiNerd

Web app

Runs in any modern browser on phones, tablets and computers. Install it to the home screen for offline use.

Open app.nautinerd.app

Android Beta

Keeps tracking, navigating and watching your anchor with the screen off. Android 8 or newer.

Download APK (9.7 MB)

Version 0.7.0 · SHA-256 d2521c93d1713dac1ffcb800228aafc61194235d07eede782694a045acf98ed6. Google Play listing coming.

iPhone & iPad

The iPhone app is in the works. Until it is in the App Store, the web app works on iPhone and iPad.

Coming soon

Good seamanship first

NautiNerd is not a certified ECDIS or type-approved navigation system. Use it alongside official charts, publications, a proper watch and your own judgement. Charts: NOAA Office of Coast Survey ENC® (public domain), U.S. Army Corps of Engineers, European inland waterway authorities (© WSV/ELWIS and others), Diretoria de Hidrografia e Navegação (Marinha do Brasil), © Kartverket; open data from Väylävirasto, Kystverket and Rijkswaterstaat. Background map © OpenStreetMap contributors. Weather: Open-Meteo.com (CC BY 4.0).