MARITIME – DEAD RECKONING & COATAL NAVIGATION CALCULATOR
Waypoint Eta
A precise tool.
What is the Waypoint Eta & How does it work?
Dead reckoning is the process of estimating a vessel’s future position by projecting its current course and speed over a given time interval. In coastal navigation, the most common variables are the distance to a waypoint and the vessel’s speed over ground (SOG), which together define the time required to reach that point.
The relationship between distance (D), speed (V) and time (t) is linear: travelling faster shortens the elapsed time, while a longer distance lengthens it. By keeping the SOG constant—an assumption that holds for short legs in calm conditions—mariners can quickly compute an estimated time of arrival (ETA) without needing complex chart work.
Because the calculation is performed in nautical miles and knots, the resulting time is naturally expressed in hours and minutes, which can be directly added to the current UTC or local time to obtain the ETA. This simple method is a staple of dead‑reckoning and coastal passage planning.
t = frac{D}{V}
t = time (hours) | D = distance (nautical miles) | V = speed over ground (knots)
Parameters
Result
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Frequently Asked Questions
How do I use the Waypoint Eta calculator?
Enter the distance to the waypoint and your vessel’s speed over ground (SOG) to get the estimated time of arrival.
What is dead reckoning in maritime navigation?
Dead reckoning is estimating a vessel’s future position by projecting its current course and speed over a given time interval.
How does changing my speed affect the Waypoint Eta?
Increasing your speed will reduce the estimated time to reach the waypoint, while decreasing it will increase the time.
Can I use this calculator for ocean navigation as well?
Yes, you can use it for both coastal and ocean navigation as long as you have the distance and SOG data.
What units should I use for distance and speed?
Use nautical miles for distance and knots for speed over ground to get accurate results.
Is there a way to factor in current or wind affecting my vessel’s speed?
This calculator assumes constant speed over ground. For more accurate estimates, consider using additional tools that account for environmental factors.
How often should I update the Waypoint Eta calculation?
Update the calculation regularly, ideally every hour or whenever there is a significant change in course or speed.
Results are for informational purposes only and do not constitute professional advice.