Understanding the polar diagram — and what it changes for your ETA
Why five knots of cruising speed is right for no course at all — and how a polar diagram turns it into a calculated arrival time.
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Knowledge for the bridge
Navigation, the course chain and sailing offline — concise articles linked to NauticCalc tools.
NMEA data on board: gateway, transports and what they give you
How onboard instruments talk to each other, why there is always a gateway between the boat network and your iPhone — and what live values really save.
Read more →Apparent wind: true wind, boat wind and the wind triangle
Why the wind on board differs from the “real” wind: apparent wind, boat wind and the wind triangle — plus how to recover true wind.
Read more →Weather on board: live data with your own API key (BYOK)
Why NauticCalc pulls live weather through your own API key (BYOK) — wind, waves, swell, current, without a subscription.
Read more →Anchor alarm & geofence: lie safely at anchor
How a GPS geofence anchor alarm works, which radius to choose and how to avoid false alarms.
Read more →Nautical conversions: nautical miles, knots, Beaufort & co.
Nautical mile, knots, Beaufort, fathom, degree — the most important nautical conversions and where mistakes happen.
Read more →Light on the horizon: calculating the sight distance of lighthouses
When a lighthouse rises “on the horizon”: geographic range from height of eye and light — and why nominal range is something else.
Read more →Passage briefing: plan the whole leg at a glance
How a passage briefing bundles ETA, tides, weather and daylight into a clear statement about the leg.
Read more →Running a ship’s kitty: settle crew expenses fairly
Shared kitty or individual settlement? How to record crew expenses and split them fairly at the end of the trip.
Read more →Hull speed log: measuring speed the classic way
How to measure speed through the water with the hull speed log from boat length and time — and cross-check it against GPS.
Read more →GPS position on board: accuracy, usefulness, privacy
How GPS supports course and logbook on board, how accurate it really is — and why your position stays local.
Read more →Backup navigation with iPhone — sensible or risky?
When backup navigation with iPhone makes sense — and when it becomes risky.
Read more →Keeping a logbook: duty, habit or convenience?
Why a logbook pays off — and how digital logging on iPhone helps.
Read more →Reading tides: HW, LW and time windows for harbour manoeuvres
Understand HW and LW and plan harbour work — with offline or live tides in NauticCalc.
Read more →Offline tides vs. live tides: what skippers need to know
When offline tides are enough — and when you need a WorldTides key.
Read more →Calculating ETA when sailing: distance, speed, departure
How to plan arrival and passage time in a traceable way — with realistic speed.
Read more →Passage time vs. ETA: typical mistakes on a leg
Why arrival time is wrong — and what to check before you leave.
Read more →Course correction step by step (with current)
From chart course to compass: the course chain and allowances in five clear steps.
Read more →Current triangle: course and speed from set and drift
Set and drift made clear: when you need the current triangle and how it fits course correction.
Read more →What is magnetic variation — and why it changes your compass course
Why the compass is not “the truth”: variation, deviation, and the course chain from rwK to steering course.
Read more →rwK, mwK, and MgK: the course chain for sailors explained
From chart course to steering compass: rwK, mwK, MgK and allowances — the basis of course correction.
Read more →Sailing without internet: what really works offline
No mobile signal on board? What NauticCalc really does offline — and where you need a network or your own API keys.
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