Etale

Étale computes French tides and currents from official SHOM data, 100% offline. MARC IFREMER atlas, SHOM Chart Datum, rigorous validations. No ads, no trackers, and no account. Built for serious coastal practices — tidal foraging, diving, sailing, sea kayaking, coastal photography — and works just as well ashore or at sea with no network.

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THE RIGHT NUMBERS, IN THE RIGHT DATUM • SHOM Chart Datum, by default in metropolitan France: shown heights match SHOM tide tables to within a few centimeters 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. • Pick your datum: SHOM CD (tide tables), LAT (theoretical chart datum), and MSL (signed mean sea level). Transparent fallback to LAT outside SHOM coverage.

EMBEDDED CURRENTS ATLAS • Animated currents map over ±6 h with a time slider, 250 m vector arrows, all French coastlines covered. • Slack water windows computed from U/V currents when available, otherwise approximated by a window around every HT/LT (tunable to your site). • 0/1/3 knot color coding (green/orange/red), standard nautical conventions.

ACTIVITY PROFILES The screen reshapes around your practice: • Tidal foraging — today's tidal range, foreshore window, and spring tide flags. • Diving — slack-water windows, conditions per coefficient, tunable duration and offset. • Sailing & boating — tide gates, highest HT (under-keel clearance), lowest LT (grounding risk), strong-current windows.

Several profiles can be active at once. Settings → My profile. 100% OFFLINE, FULLY RESPECTFUL • No data ever leaves your phone. • No analytics, no third-party SDK, and no tracker. • No account, no password, no advertising. • No remote push notifications. Tide 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, on a cliff.

OUTDOOR READING MODE Sun button at the top of Home: switches to a high-contrast full-screen view with very large digits (~96 pt), built for field conditions (full sun, wet fingers, gloves). LANGUAGES • Interface: French + English. • Embedded documentation (glossary, methodology): French + English. SOURCES & QUALITY • MARC IFREMER atlas — Pineau-Guillou, L. (2013). Validation des atlas de composantes harmoniques de hauteurs et courants de marée. Ifremer report, 89 p. • TICON-4 — Hart-Davis, M.G., Dettmering, D., Seitz, F. (2025). SEANOE, doi:10.17882/109129. CC-BY 4.0 license. • References Altimétriques Maritimes — Shom, 2025. doi:10.17183/MAREE_COURANTS_RAM. Etalab v2.0 open license. • pyfes — AVISO/CNES/LEGOS, BSD-3.

Typical precision: about 5 cm RMS compared to the SHOM tide chart (Brest, 24 h, 3.97 cm). ~Ten centimeters in grid mode across metropolitan France.

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IMPORTANT Étale is a planning aid for coastal leisure. A pure harmonic model — weather (storm surge, wind, barometric pressure) is not factored in. During storms, allow an extra ±15 to 30 cm margin. Étale is not a replacement for certified instruments for professional marine navigation. Available for metropolitan France + Corsica. DOM-TOM and foreign coastlines coming in later versions. Website and complete methodology: https://etale.fbriol.workers.dev.