km/hr or kn?

[whichway]

Hi

Do you use km/hr or knots when talking about teh speed of you boat.

I use km/hr, but a mate who has a bay cruiser always insists on knots.

Does it matter which you use.

Whichway.

[Spaniard_King]

Knots on sounder and KLm/hr on GPS

Garry

[Tony_N]

My Furuno GPS is set on kliks. The mental conversion from knots to kph to give the speed some benchmark/relevance to me is too hard. #I think REAL navigators use knots

[seatime]

Doesn't matter so much for general small boat use, local fishing, that kinda thing. Depending where your GPS or sounder was manufactured, they'll read in kts or klms.

If travelling large distances and using Admiralty type charts, you'll need to use knots (nautical miles/hour).
Distances on paper charts or Raster scanned charts are measured in nautical miles, in the case of paper charts, off the latitude scale, Raster calculate automatically.
This is because the earth's curved surface is measured in nautical miles, e.g. 1nm = 1 minute on the latitude scale, 60nm = 1 degree of latitude.

Kilometers don't really allow for curvature, more for flat surfaces, so for short journeys and it's OK to use klm/hr.

regards
Steve.

[triman]

A knot is 1 nautical mile per hour or about 1850 metres an hour, give or take.
So 1 knot is just a tad under 2 km/hr.
Note that a kilometre is a fixed distance of 1000 metres while a nautical mile is slightly variable, depending upon the latitude. At the Equator a nautical mile is 1842 metres, at the pole its about 1861.

[Kerry]

....Note that a kilometre is a fixed distance of 1000 metres while a nautical mile is slightly variable, depending upon the latitude. At the Equator a nautical mile is 1842 metres, at the pole its about 1861.

The nautical mile is defined as (exactly) 1852 metres and all nations have adopted this value since 1929.

[seatime]

whichway,

You'll notice the wind speed predictions on the more reputable sites, bom, seabreeze, buoyweather, use knots not klms, as knots are a nautical measurement.

Whereas some media like TV Ch 10 use klm/hr, mostly for landbased observations and predictions, but some marine forecasts. They're more for landlubbers, as they can relate to kms in their cars more easily.

Jetskis have klm/hr on the speedo, as they're a motorbike on water
although the speed restrictions are legislated as knots

When talking boat speed, I prefer knots (old school) so I can refer to a chart and calculate fuel consumption if needed, tho klm/hr does sound faster.
At the end of the day, use whatever you're most comfortable with

[eugah]

My speedo & trip computer are set up for knots, but i have my GPS set up KM as i fing it easier to visualize 100 metres rather than .048 knot when looking for my spots.


Adrian

[Cheech]

I am obviously not a real navigator then because I use kph and also metres in depth.

I understand all 3 units. My first car was actually in mph, and I did a lot of sailing in my youth with knots. But for smallcraft boating, it seems a lot easier and readily understood by everyone when you talk metric. Same with fuel economy, I talk k per litre rather than litres per hour.

[mirage]

Hi Guys,

I'm sorry but I have to make a comment here and correct some of the cr@p that's coming out.

1 Nautical Mile is 1 minute of longitude (not latitude) when measured at the equator and ONLY at the equator, as a minute in longitude decreases in distance as you head North or South. Therefore 1 degree of longitude at the equator is 60 Nautical Miles.

A Nautical Mile has never been and will never be a variable figure.

As to the original question, if you are happy talking about how fast your pride and joy goes in km/h then go for it. Knots just makes it far easier for navigating off nautical charts etc. Personally I wish boat magazines would use knots not km/h when doing boat tests. 53km/h means nothing to me when I'm thinking about boats or aircraft for that matter.

Any GPS that I know can be changed between km/h, mp/h or knots!

Cheers, Scotty.

[StevenM]

Doesnt matter you are still doing the same speed at the end of the day

but for the record

knotts

[dogsbody]

Just keep it in knots saves confusion. Whats next do you weigh your fish in kg or lbs.
Dave.

[seatime]

mirage

where's the cr@p, maybe you should check your facts.

Latitude is an arc, measured from the centre of the earth, North and South of the equator.
Longitude is an arc measured at the poles, East and West of Greenwich.
Lines of Longitude are great circles, that is, their planes pass through the centre of the earth.
The only great circle line of latitude is the equator, as it's the only one who's plane passes through the centre of the earth. Parallels of latitude are then measured as arcs N and S of the equator. These are small circles.

Navigation calculations of position are made in units of arc, degrees and minutes. It is convenient for navigators to use as a unit of distance, the length of a minute of arc of a great circle upon the earth's surface.
So, a nautical mile is taken as the length of a meridian which subtends an angle of 1 minute at the centre of the earth.
As the earth is not a perfect circle, it's modified so that 1 minute of geographical latitude is equal to 1 nautical mile (1853 metres) at any given latitude.

What you're refering to is a geographical mile, which is 1 minute of arc of the equator, or the length of the equator which subtends an angle of 1 minute at the centre of the earth.

At the equator, 1 minute of longitude is equal to 1 GEOGRAPHICAL MILE or 1855.3 metres.

You can apologise anytime now, thanks.

regards
Steve

[Kerry]

Hi Guys,

I'm sorry but I have to make a comment here and correct some of the cr@p that's coming out.

1 Nautical Mile is 1 minute of longitude (not latitude) when measured at the equator and ONLY at the equator, as a minute in longitude decreases in distance as you head North or South. Therefore 1 degree of longitude at the equator is 60 Nautical Miles.

A Nautical Mile has never been and will never be a variable figure.

Cheers, Scotty.

Cr@p coming out #needing correcting Well then lets correct this cr@p!

What you have desicribed is not a Nautical mile but a Geographical mile this being 1/60th of a degree (in Longitude) of the earth's equatorial circumference.

A Nautical mile is one minute of arc in latitude of a great circle.

Regards, Kerry.

Edit: PS Gelsec Ah you already said that
# #

[Brissyguy]

Well our old Caribbean has a speedo in mph, a sounder set on km/h and the GPS reads in knots lmfao...