Meridian Nav

Meridian is a celestial navigation toolkit built at sea by a working deck officer — fully offline, because mid-ocean is exactly where you need it.

SIGHT REDUCTION Compute Hc, Zn and intercept for the Sun, Moon, four planets and 63 navigational stars. Enter your DR position, date/time and sextant altitude — get your line of position.

COMPASS ERROR Check gyro error by azimuth of any celestial body — the daily routine, without the almanac and tables. Magnetic variation (WMM2025) is built in for magnetic compass work.

STAR FINDER A polar sky-dome view shows exactly which bodies are observable right now from your position — plan your twilight sights before stepping out on the bridge wing. Includes an azimuth-scatter view for picking the best LOP geometry.

SUN / MOON Rise, set, meridian passage and twilight times for any position and date.

MARINE CHART — FULLY OFFLINE A custom offline vector chart with world time-zone (ZD) boundaries, DST awareness, ports and waypoint routes. Import route files (.rtz / .rou) straight from your ECDIS.

CLOCK PLAN Generate the entire voyage's retard/advance schedule from your route — including DST transitions and solar-zone departures. Reorder or edit the changes, then export a clean calendar-style PDF or Excel notice, ready to post on board.

UNIT CONVERTER The conversions a navigator actually uses, in two taps.

ACCURACY & VALIDATION Every body — Sun, Moon, planets and 63 navigational stars — is cross-checked against JPL ephemeris data (the same source behind the official Nautical Almanac) to arc-minute agreement. Star positions are computed for the current date from the ESA Hipparcos catalogue. Sun azimuth verified at sea against a ship's bridge calculator, and against NOAA's solar calculator (0.000° difference).

MADE FOR Deck officers who want a fast backup and sanity check, cadets and officers studying celestial navigation, and anyone who believes a navigator should still be able to find a ship without a satellite.

No account. No ads. No subscription. No internet required. One-time purchase.

IMPORTANT Meridian is a reference and training aid for celestial navigation. It is not a certified navigation system and does not replace official nautical publications, charts, or type-approved equipment.