TOP NAVIGATION FORMULAS EVERY DECK OFFICER SHOULD KNOW You don’t need… — RhumbFleet — Connect

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⚓ TOP NAVIGATION FORMULAS EVERY DECK OFFICER SHOULD KNOW
You don’t need to memorize hundreds of equations.
But these? You should know them cold. 🧭
📐 BASIC NAVIGATION
1️⃣ Distance D = V × T
2️⃣ Speed V = D / T
3️⃣ ETA ETA = Present Time + Distance / Speed
4️⃣ Latitude → Distance 1° Latitude = 60 NM
1′ Latitude = 1 NM
🌊 CURRENT & DRIFT
5️⃣ Current Speed Drift = Distance / Time
6️⃣ Set & Drift Set = direction of current Drift = current speed
Always remember: Course through water ≠ Course over ground
🧭 COMPASS
7️⃣ True Course True = Compass + Deviation + Variation
8️⃣ Compass Error CE = True − Compass
Know the signs — this is where mistakes happen.
⚓ UNDER KEEL CLEARANCE
9️⃣ UKC
UKC = Depth − Draft − Squat − Safety Margin
And remember:
Speed ↑ → Squat ↑
🚢 MANOEUVRING
🔟 Rate of Turn
ROT = Change of Heading / Time
A simple formula — but extremely important when controlling a large vessel in restricted waters.
🎯 COLLISION AVOIDANCE
1️⃣1️⃣ CPA — Closest Point of Approach
CPA tells you how close another vessel will come if both maintain their present motion.
1️⃣2️⃣ TCPA — Time to CPA
TCPA tells you how much time remains before that closest approach.
And one practical rule:
Small CPA + Short TCPA = Act early.
☀️ CELESTIAL NAVIGATION
1️⃣3️⃣ Corrected Altitude
Ho = Hs + Corrections
Where corrections may include:
Index correction
Dip
Refraction
Semi-diameter
🔥 THE GOLDEN NUMBERS
1° Latitude = 60 NM 1′ Latitude = 1 NM 1 NM = 1 minute of latitude 1 knot = 1 NM/hour
These four alone save a surprising amount of time on the bridge.

⚓ RhumbFleet

Professional Maritime Knowledge. Real Experience. Continuous Learning.

RhumbFleet — Connect

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