Automated Navigation Calculators Bridge Support

Quick reference tools designed for bridge teams and superintendents to support voyage planning, monitoring, and training. All computations are approximate and must be verified against official publications and the ship's instruments.

ETA & Steaming Time Use distance, speed and zone descriptions to estimate passage and arrival.

Rhumb / GC / DR Constant course, great circle and dead reckoning position.

Wind / Compass / Sun True & relative wind, compass / gyro, sunrise & sunset.

Disclaimer

These tools are for reference and training only. They do not replace approved ECDIS, nautical tables, or the professional judgement of the Master and officers.

Tips

Use decimal degrees (e.g. 14.50° = 14°30').
Use knots for speeds and nautical miles for distances.
Cross-check results with your own manual calculations.

1. ETA & Steaming Time Calculator

Compute steaming time from distance and speed, and estimate ETA in both departure and arrival zone descriptions.

Steaming Time

Distance and speed → hours & minutes

Distance (NM)

Speed (knots)

ETA from Departure with Zone Description

Distance, speed, departure date/time + ZD (Dep & Arr) → ETA

Distance (NM)

Speed (knots)

Departure Date & Time (Departure ZD)

Zone Description – Departure (hours)

Zone Description – Arrival (hours)

Nautical convention: ZD West is positive, ZD East is negative.
Example: 120°E ≈ ZD -8, 045°W ≈ ZD +3. Formula used: Local Time = GMT − ZD.

2. Rhumb Line Calculator (Mercator)

Compute approximate rhumb line distance and course between two positions (constant compass course).

Rhumb Line Distance & Course

Decimal degrees only (North & East positive, South & West negative)

Lat 1 (°)

Lon 1 (°)

Lat 2 (°)

Lon 2 (°)

Uses Mercator sailing (Earth radius ≈ 3440 NM). Suitable for most ocean passages outside high latitudes.

3. Great Circle Calculator

Compute great circle distance and initial course between two positions (shortest path on the sphere).

Great Circle Distance & Initial Course

Decimal degrees only

Lat 1 (°)

Lon 1 (°)

Lat 2 (°)

Lon 2 (°)

Based on haversine formula and spherical trigonometry. For routeing, always cross-check using ECDIS / official tools.

4. True & Relative Wind Calculator

Resolve true wind and relative (apparent) wind using basic vector addition.

True Wind → Relative Wind

Given true wind (from) + ship course/speed → relative wind as felt on deck.

Ship Course (°T)

Ship Speed (kn)

True Wind Direction (°T, FROM)

True Wind Speed (kn)

Relative Wind → True Wind

Given relative wind from bow + ship course/speed → true wind (from).

Ship Course (°T)

Ship Speed (kn)

Relative Wind Bearing (° from bow)

Relative Wind Speed (kn)

5. Compass Correction & Gyro Error

Quick helper for basic TVMDC conversions and gyro error.

TVMDC Converter

True (T), Variation (V), Deviation (D), Magnetic (M), Compass (C)

True Course / Bearing (°T)

Variation (°)

Var E/W

Deviation (°)

Dev E/W

Compass Course / Bearing (°C)

Sign convention: East variation/deviation is positive. Formula used: T = C + D + V.

Gyro Error

Compare gyro heading with true direction to same object.

Gyro Heading / Bearing (°G)

True Course / Bearing (°T)

Gyro error is "E" when Gyro < True, "W" when Gyro > True (after normalising 0–360°).

6. Dead Reckoning (DR) Position

Compute new DR position from an initial position, course, speed and elapsed time (plane sailing approximation).

DR Position Calculator

Decimal degrees only (North & East positive, South & West negative)

Initial Latitude (°)

Initial Longitude (°)

Course Steered (°T)

Speed (knots)

Time (hours)

+ Minutes

Plane sailing approximation: ΔLat and departure with mean latitude. Suitable for short to moderate distances.

7. Sunrise & Sunset

Approximate sunrise and sunset times for a given date, position and zone description (ZD).

Sunrise / Sunset Calculator

Based on standard astronomical approximations (civil horizon −0.833°).

Date (UTC / GMT)

Latitude (°)

Longitude (°)

Zone Description ZD (hours, West +, East -)

Times are approximate. At high latitudes there may be no sunrise or no sunset for certain dates.