Blog
Navigation, the course chain and sailing offline — concise articles linked to NauticCalc tools.
Sextant altitude and observed altitude are easily 20 arcminutes apart. Where that comes from, why the wrong limb costs 32 nautical miles — and what noon latitude alone is good for.
Read more →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.
Read more →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 →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 →Why NauticCalc pulls live weather through your own API key (BYOK) — wind, waves, swell, current, without a subscription.
Read more →How a GPS geofence anchor alarm works, which radius to choose and how to avoid false alarms.
Read more →Nautical mile, knots, Beaufort, fathom, degree — the most important nautical conversions and where mistakes happen.
Read more →When a lighthouse rises “on the horizon”: geographic range from height of eye and light — and why nominal range is something else.
Read more →How a passage briefing bundles ETA, tides, weather and daylight into a clear statement about the leg.
Read more →Shared kitty or individual settlement? How to record crew expenses and split them fairly at the end of the trip.
Read more →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 →How GPS supports course and logbook on board, how accurate it really is — and why your position stays local.
Read more →When backup navigation with iPhone makes sense — and when it becomes risky.
Read more →Why a logbook pays off — and how digital logging on iPhone helps.
Read more →Understand HW and LW and plan harbour work — with offline or live tides in NauticCalc.
Read more →When offline tides are enough — and when you need a WorldTides key.
Read more →How to plan arrival and passage time in a traceable way — with realistic speed.
Read more →Why arrival time is wrong — and what to check before you leave.
Read more →Compass → magnetic → true → through the water → over ground: the signs and two solved exercises, forwards and backwards.
Read more →Set and drift made clear: when you need the current triangle and how it fits course correction.
Read more →Why the compass is not “the truth”: variation, deviation, and the course chain from rwK to steering course.
Read more →From chart course to steering compass: rwK, mwK, MgK and allowances — the basis of course correction.
Read more →No mobile signal on board? What NauticCalc really does offline — and where you need a network or your own API keys.
Read more →