Étale: Tides & Currents

French tides and currents from official SHOM data. 100% offline, no ads, no trackers. Built for tidal foraging, diving, sailing and coastal photography.

Étale computes French tides and currents from official SHOM data, fully offline. MARC IFREMER atlas, SHOM Chart Datum, rigorous validation. No ads, no trackers, no account.

Built for demanding coastal practice — tidal foraging, diving, sailing, sea kayaking, coastal photography — and it works just as well ashore as at sea, with no network.

LOOK FOR A WINDOW, NOT A TIMETABLE

You know the conditions you go out in — water height, slack current, coefficient, time of day, minimum duration. Describe them, and Étale searches up to 30 days ahead for the moments that meet all of them, offline, at a port or at any covered point.

• Quick starts for diving, tidal foraging and sailing; every field stays editable. • The first three searches are free, then a one-time purchase unlocks them all — no subscription, Family Sharing. Everything else stays free: tides, currents, forecast, widget, alerts.

THE RIGHT NUMBERS, IN THE RIGHT DATUM

• SHOM Chart Datum by default in metropolitan France: displayed heights match the SHOM tide tables to within a few centimetres at every named French port. • MARC IFREMER grid atlas (Pineau-Guillou, 2013), 250 m native resolution, 33 harmonic constituents per cell. • TICON-4 port constituents (Hart-Davis et al., 2025, CC-BY), fitted to long-term REFMAR/SHOM observations. • Your choice of datum: SHOM CD (tide tables), LAT (theoretical chart datum), or signed mean sea level. Transparent fallback to LAT outside SHOM coverage.

THE CURRENTS ATLAS, EMBEDDED

• Animated currents map over ±6 h with a time slider, 250 m vector arrows. • Slack water computed from U/V currents wherever the atlas covers the point; elsewhere the app says so rather than approximating. • Colour coding at ≤ 1 knot, 1–3 knots, > 3 knots (green, orange, red). • Coverage: eastern Channel, north Brittany, Cotentin and the Bay of the Seine, south Brittany, Loire and Vendée, Aquitaine and the Basque coast.

ACTIVITY PROFILES

• Tidal foraging — today's range, foreshore window, spring tides flagged. • Diving — slack-water windows, tunable in duration and offset to suit the site. • Sailing and boating — highest high water, lowest low water, strong-current windows between two slacks.

Several profiles can be active at once: Settings → My profile.

FULLY OFFLINE

• No data ever leaves your phone: no analytics, no third-party SDK, no tracker. • No account, no password, no advertising. • No remote push notifications. High and low water alerts are scheduled locally by iOS. • Download your coastal zones over Wi-Fi before you leave: the app then works in dead zones, at sea, at the foot of a cliff.

OUTDOOR READING MODE

The sun button at the top of the Home screen switches to a high-contrast full-screen view with very large digits — for full sun, wet fingers and gloves.

SOURCES

• MARC IFREMER atlas — Pineau-Guillou (2013), Ifremer. • TICON-4 — Hart-Davis et al. (2025), CC-BY 4.0 licence. • Références Altimétriques Maritimes — Shom (2025), Etalab v2.0 open licence. • pyfes — AVISO/CNES/LEGOS, BSD-3 licence.

Typical measured accuracy: about 5 cm RMS against the SHOM tide tables at a named port (Brest, 24 h: 3.97 cm). Around 10 cm in grid mode.

IMPORTANT

Étale is a planning aid for coastal outings. The model is purely harmonic: weather — storm surge, wind, barometric pressure — is not accounted for. During storms, allow an extra ±15 to 30 cm.

Étale is not a replacement for certified instruments for professional marine navigation.

Available for metropolitan France and Corsica. Tides cover 592 European ports; currents cover the coastlines listed above. Overseas territories and foreign coastlines in later versions.

Website and full methodology: https://etale.fbriol.workers.dev