The Offshore Voyaging Reference Site

Why We Use Knots and Nautical Miles

A nice post over at Sailing Scuttlebutt on why we don’t use kilometres at sea and shouldn’t be using metres per second in marine forecasts.

I couldn’t agree more.

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Stein Varjord

Hi John,

I do use Nautical Miles and knots at sea, of course, and I do agree that the reference to the longitude scale was useful on paper maps. However, I think my use is based on habits from that time, not really good reasons, since I must disagree with every other reason he mentions. Mentioning the absolutely useless furlongs, cables and more proves my point:

He seems to put value in tradition. I do too, but not for this type of topic. Measuring systems must only be chosen by performance, what is the most functional. So, Nautical Miles have one single link to paper maps, which is not really relevant for most people today. Metric misses this irrelevant benefit, but has the advantage of being intuitively understood by far more people, and being far simpler to learn. Those are arguably superior benefits.

His point seems even more related to a resistance to modernising, as he gives a rant about being coerced towards metric away from the imperial measurement system, which was annoying and useless even when it was developed, in medieval times. I can understand using it because of habits, which is why I’ll keep using Nautical Miles and a 360 degree compass. Still, I don’t think functionality and the future is on my side there…

Frode Rognstad

Knowing simple relationships between systems can help, for as long as we’re likely to be exposed to both. For instance, wind speed in m/s can be doubled to get knots (rounded). This has helped me many times, as I’m still thinking knots, while weather forecasts give me m/s.