km's vs nautical miles

[mmmouse]

why do so many boaties talk distances on the water in km's? i guess when ur gps does all the hard work it's just like driving a car...... but what if ur gps gives up the ghost and u have to navigate home safely? all the increments down the side of a nautical chart are in nautical miles and converting to km's is a pain in the backside!...... remembering that a gps is an aid to navigation all planning of long range trips and trips into new areas should be done on paper charts using nautical miles as the unit of measurement, or am i just old fashioned and out of touch with reality?:-?

[Lancair]

Mouse, I thnk its just that new boaties dont have a clue how long a nautical mile is and dont care to find out. They dont use paper charts, only GPS and therefore set their GPS to show Km's because thats all they understand.
When they get into trouble at sea and can only tell the coastguard that they are 25km from point danger but dont know how many miles that is, or how to read the lat/long of the gps, or even know which direction other than east-ish, theyll be in deeper trouble. Boaties should use nautical miles, should carry and use paper charts, should plot their positions on paper charts with bearings from known landmarks etc etc, because if their GPS dies or the US Govt decide to turn GPS off for whatever reason, they're going to be lost.
I agree with you completely, we're on the water, the international standard is nautical miles, thats what we use. I have always used and will always use, I dont think we're out of touch with reality, as reality is nautical miles, we're just old school. :-)

[finga]

Why are most sounder set to metres??

[Marlin_Mike]

http://www.online-calculators.co.uk/conversion/nauticalmileskilometres.php

that might help those who don't know

Mike

[FishHunter]

I would imagine that most people use meters because as a metricated system thats what we understand.
I use km but I know that there is approx 1.8 km to 1 nautical mile and 3.3 foot to a metre and 6 foot to a fathom and can work the convetsions in my head. I just assumed most people did the same.
maybe its time to turn my sounder to miles.

[Geoff-]

furlongs per fortnight is where it's at. you nautical mile boys!! *shakes head*


:)

nautical miles is the real measure when you're on the water, but in a metricated country I can understand people defaulting to kilometres because they're more familiar with it. I think being able to translate between the two is important because it demonstrates awareness of different units of measurement.

I'm happy with nautical miles and knots but when I worked out the top speed of our boat I converted it to km/h because that means more to me :D

[Lucky_Phill]

You'll find that the metric system of measure is used more often on land than water. ( driving cars, speed limits , distance road signs etc )

I was brought up on Imperial but talk metric 99% of the time.

Telling some one you are 2k's off shore is easy, as they ( younger folks and older that used metric on land ) will understand, rather than switching to NM.

I don't even use Knots for speed... ??

I set my GPS to metric, sounder to meters, kilometers per litre ( litres per hour ) and I convert my chart measuring to metric. Come to think of it, the only imperial I use is tyre pressure in the trailer wheels.... 45psi :) :)


I find it way too easy..... say, the fishing spot is 100k's offshore and traveling at 50kph ( average ) I'll get there in 2 hours.... tried to do that with knots and miles ???? :(

AS long as the system you use, you understand and you can convey that to those that matter ( Search & Rescue etc ), then that is all that matters.

Then again... Green Ginger Wine ( necessary fishing liquid ) comes in 700ml bottles. :) :)



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[maimai]

furlongs*shakes head*



haha, i still use that with chains, i convert the speedo in the car with chains, why use KPH, its too easy now days;D

[marty666]

really when was the last time the gps sat network was switched off. at the end of the day you should know where you are going and in your head have a good idea of compass bearings to get yourself home, but i am becoming complacent like the rest and relying on the trusty old sat nav because i do know how to convert if need be and i all was take notice of bearings and return bearings just in case.

[mmmouse]

Why are most sounder set to metres??
finga i agree with sounders being set to metres as all soundings on a chart are in metres as are all heights of mountains etc

[PinHead]

why do so many boaties talk distances on the water in km's? i guess when ur gps does all the hard work it's just like driving a car...... but what if ur gps gives up the ghost and u have to navigate home safely? all the increments down the side of a nautical chart are in nautical miles and converting to km's is a pain in the backside!...... remembering that a gps is an aid to navigation all planning of long range trips and trips into new areas should be done on paper charts using nautical miles as the unit of measurement, or am i just old fashioned and out of touch with reality?:-?

correct..each minute of latitude = 1 nautical mile..but what do you do when you go across the chart..longtitude is not a measurement .

[mmmouse]

correct..each minute of latitude = 1 nautical mile..but what do you do when you go across the chart..longtitude is not a measurement .
true longitude represents time not distance...but if u take a line from point a to point b and take that measurement to the increments on the side of the chart it will give u the distance in nm of that line. it's important to measure the distance of that line with the increments directly across from its position on the chart as the increments actually change slightly between the top and bottom of the chart because of trying to project a round object onto flat paper!!!

[D river]

R u serious mate if your using charts now days then your probly using a sail too so get out of the way when I'm heading 100km out to sea to fish 70m of water for red fish. I can see land from there and know what I'm looking at and bearing if its that bad and I also know lights and point of aim off them for night time hell I use them to navigate my way home more than the gps and be gabby-googled if any idiot would try use his compass at sea unless his gps was bought on ebay n failed. Do you measure your fuel in gallons too even though the bouser reads in litres

[tigermullet]

R u serious mate if your using charts now days then your probly using a sail too so get out of the way when I'm heading 100km out to sea to fish 70m of water for red fish. I can see land from there and know what I'm looking at and bearing if its that bad and I also know lights and point of aim off them for night time hell I use them to navigate my way home more than the gps and be f*cked if any idiot would try use his compas at sea unless his gps was bought on ebay n failed. Do you measure your fuel in galons too even though the bouser reads in litres


You can see land from 100km out? Even if you were 10km out, the horizon should only be visible from 8 metres up, approximately.

[Marlin_Mike]

R u serious mate if your using charts now days then your probly using a sail too so get out of the way when I'm heading 100km out to sea to fish 70m of water for red fish. I can see land from there and know what I'm looking at and bearing if its that bad and I also know lights and point of aim off them for night time hell I use them to navigate my way home more than the gps and be gang-googled if any idiot would try use his compas at sea unless his gps was bought on ebay n failed. Do you measure your fuel in galons too even though the bouser reads in litres


You can see land from 100km offshore??????????????? $hyte you must have good eyes. Been eating lotsa carrots have we??????

Idiot for using a compass at sea?????????????????? I aint even gonna comment on that one.

[maimai]

R u serious mate if your using charts now days then your probly using a sail too so get out of the way when I'm heading 100km out to sea to fish 70m of water for red fish. I can see land from there and know what I'm looking at and bearing if its that bad and I also know lights and point of aim off them for night time hell I use them to navigate my way home more than the gps and be googled if any idiot would try use his compas at sea unless his gps was bought on ebay n failed. Do you measure your fuel in galons too even though the bouser reads in litres

D river, i have been fishing most of my walking life, I would hate to be heading home at night 70ks off shore trying to get around reefs just by going on the headland lights, bad enough during the day, there is a few reefs that pop out meters at low tide, believe me mate, it is very scarey without a GPS, as for the compass, well this is the second most tool i use on the boat
good luck

[rob fish]

So Driver mate what do you do when your plotter breaks down and its raining?or the fog moves in? Surely your reply was a joke.

[TheRealAndy]

R u serious mate if your using charts now days then your probly using a sail too so get out of the way when I'm heading 100km out to sea to fish 70m of water for red fish. I can see land from there and know what I'm looking at and bearing if its that bad and I also know lights and point of aim off them for night time hell I use them to navigate my way home more than the gps and be googled if any idiot would try use his compas at sea unless his gps was bought on ebay n failed. Do you measure your fuel in galons too even though the bouser reads in litres

Ha ha ha, and they call us motorbike riders temporary australians!!

!

[tunaticer]

R u serious mate if your using charts now days then your probly using a sail too so get out of the way when I'm heading 100km out to sea to fish 70m of water for red fish. I can see land from there and know what I'm looking at and bearing if its that bad and I also know lights and point of aim off them for night time hell I use them to navigate my way home more than the gps and be googled if any idiot would try use his compas at sea unless his gps was bought on ebay n failed. Do you measure your fuel in galons too even though the bouser reads in litres

Never in my life have I come across you D river. I honestly hope we never cross paths in person to realise just how far down the human species has descended. I truly hope that if your GPS fails, your radio and mobile phone dies, and maybe then you would realise the importance of navigation without electronic aides.

[Geoff-]

seriously guys give the guy a break, you'd do well to heed his advice and get out of his way.

he's rushing straight to the scene of the accident!



:LMAO:

[finga]

Y
Then again... Green Ginger Wine ( necessary fishing liquid ) comes in 700ml bottles. :) :)
LP.
I suppose you measure distances in millimetres too. Only nancy boys buy those teeny weeny bottles.


You can see land from 100km offshore??????????????? $hyte you must have good eyes. Been eating lotsa carrots have we??????

Did you know the old wives tale of carrots and eye sight was started in the second world war by the British??
They had their new radar system going and it was playing havoc on the Nazi night air strikes over Britain as the British knew exactly where the Nazi's were and how many planes their were.
Now the pommy's wanted to keep this radar set-up hush, hush so they started the rumour that their pilots could see in the dark by eating lots of carrots....and it worked

[D river]

Spare hanheld garmin gps with c map card in it plus iphone with navonics app means I'll be doing fine without needing to use my compass n def wont be needing charts thats for sure, Its not called stupid its called well prepared. And if you dont belive that land is visible out that far then you must live somewhere down south where it aint worth being, 100km out from shute i can see the edward islands, hamo, whitsunday, hook, lindamin, hayman,120km out from able point can see bowen, glouster, double cones,80km out from lucinda can see palm group, hinschenbrook, if you cant see these then def get out of the way cause you'd be really struggling to use a compass in the swell. And jack seriously mate what r ya guna do really, I'm no hero ey but you'd def not enjoy that if thats how you'd start our conversation. My original reply was a joke but obviously none of you seen it in that light which tells me you prob all are sailors or victorians n need to be on a different forum so to continue on the path chosin Be damned if I'd be relying on charts n compass to get me through the reef up here at night, thats the time you anchor up n fish with a few beers then sleep, I trust nothing at night up here that I dont know like the back of my hand. And as far as being able to navigate without aids for my job I have to be able to navigate at night with no lights through rainforest n hills with a 35kg+ pack on using nothing but a map n compass and do it without sleep for 24hrs so I know how retardid you have got to be not to have a back up source of gps, why would any1 want to do it the hard way in this day and age.

[Kero]

Spare hanheld garmin gps with c map card in it plus iphone with navonics app means I'll be doing fine without needing to use my compass n def wont be needing charts thats for sure, Its not called stupid its called well prepared. And if you dont belive that land is visible out that far then you must live somewhere down south where it aint worth being, 100km out from shute i can see the edward islands, hamo, whitsunday, hook, lindamin, hayman,120km out from able point can see bowen, glouster, double cones,80km out from lucinda can see palm group, hinschenbrook, if you cant see these then def get out of the way cause you'd be really struggling to use a compass in the swell. And jack seriously mate what r ya guna do really, I'm no hero ey but you'd def not enjoy that if thats how you'd start our conversation. My original reply was a joke but obviously none of you seen it in that light which tells me you prob all are sailors or victorians n need to be on a different forum so to continue on the path chosin Be
damned if I'd be relying on charts n compass to get me through the reef up here at night, thats the time you anchor up n fish with a few beers then sleep, I trust nothing at night up here that I dont know like the back of my hand. And as far as being able to navigate without aids for my job I have to be able to navigate at night with no lights through rainforest n hills with a 35kg+ pack on using nothing but a map n compass and do it without sleep for 24hrs so I know how retardid you have got to be not to have a back up source of gps, why would any1 want to do it the hard way in this day and age.


D river,
Funny how everyone else here couldn't see the joke!
Have you noticed that you're the only one who is doing it right & everyone else is wrong? ;)
I'm sure there's a more suited forum for you out there somewhere.

[Lucky_Phill]

Every one should remember that this is a G rated site and name calling is against the rules.

Hence edited posts.

The best I have done is see the tops of land ( mountains ) from about 44k's out, on a very clear day.

GGW is 700ml or 8.... metric swigs .... :) :)



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[Isaac]

I find it way too easy..... say, the fishing spot is 100k's offshore and traveling at 50kph ( average ) I'll get there in 2 hours.... tried to do that with knots and miles ????


Phil,

The knot is a unit of speed equal to one nautical mile per hour.

For you example your fishing spot is 30nm offshore and you are travelling at 15knots it will take you 2 hours to get there. Some more useful info here http://en.wikipedia.org/wiki/Knot_(unit)

Cheers Isaac

[Lucky_Phill]

Thanks Isaac.

I do understand the system, but for me, metric is the go.

On land ( where we spend the vast majority of our time ) we talk, write and see metric, so why confuse the brain.... ( read... my brain :) )

Here's a red herring:-

If you are driving up a beach in a current motor vehicle that is obviously graded in metric ( below high water mark and therefore, technically.. on / in the water ) and you break down. Do you tell assistance ( via UHF Radio ) you are 10 k's south of Indian Head or 5.399 568 034 6 nautical miles south of Indian Head ? ;D :o 8-)

Yes I know........ but... with this lousy weather, anyone could go a little crazy !!! ;) ;D ;D




LP


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[honda900]

Just pulled my chart out and it has both a kilometre and nautical mile scale, so guess I will be fine either way. sort of makes the argument somewhat redundant.

regards
Honda.

[mitch92]

Phil,

The knot is a unit of speed equal to one nautical mile per hour.

For you example your fishing spot is 30nm offshore and you are travelling at 15knots it will take you 2 hours to get there. Some more useful info here http://en.wikipedia.org/wiki/Knot_(unit (http://en.wikipedia.org/wiki/Knot_%28unit))

Cheers Isaac


Something dont add up there?? phil said fishing 100k's out? 100km = 53.996nm 50Km/h = 26.998 knots??

Sure can travel at 15 Knots, and travel 30 mile in 2 hours, but you'll be 24ish miles roughly from phil??

Unless yours was another example?

Cheers
Mitch

[testlab]

Try aviation...

Length is in metres (as in runway length, visibility, etc).
Point to point distance is in nautical miles.
Speed is in knots
Altitude is in feet
Fuel is in litres (or imp gallons or US gallons)
Weight is in kgs (or lbs)

When on the water I always carry charts. Always have and always will. I prefer paper charts to give me a 'big picture' view of an area I may not know intimately. I use GPS (and often radar too) to provide me with "where am I now" information rather than "where am I going" (so I don't need to keep changing ranges on the GPS).

When venturing to an unknown location or making a voyage I always mark up charts with stuff I need to know and can see at a glance.

I have taken hand-held GPS with me as backup when flying and on the water. I can honestly say when conditions are crook they are bloody difficult to use. The signal drops in and out and the displays are hard to read when being tossed about (I am talking about in-cabin or flybridge helm stations - the signal should be more consistent in an open helm station but the ride will be worse in smaller boats).

Paper charts are not brillant in those conditons either but they make it far more easy to use a handheld GPS. Instead of staring at a tiny screen under crap conditions you can read off a co-ord/spot on the GPS and then put a finger "on the spot" on the chart and instantly see the big picture including planning a place to hole up if need be, the need to change course to avoid areas where conditions may be worse (bommies, shoals, etc).

Obviously everbodys experience and local knowledge is relevant to them, but there have been times when I have been in familar waters and become disorientated. The GPS has been terrific for helping out then, but when teaching some of my less experienced friends I turn off the GPS and say "now what?"

Oh and to get back on topic... offshore I use distance in Nm and depth in metres. It matches whats on most naval charts these days and I am familar with it. On enclosed waters I may use kms and metres if it matches the local waterways maps.

[trueblue]

Just to change things up a bit......

i was pulled up by water police, and asked to show my navigation equipment. Being clued up on why they were asking i went straight for my chart etc.

They then asked me to calculate a return course compass bearing.

After being satisfied, they then reminded me that I must always consider the gps as a secondary aid to navigation, and that the primary means of navigation should always be continuous knowledge of current position, and ability to navigate home by compass bearing / time tracks.

was he going over the top a bit, yes i think he was.

was he within his rights under the law to ask about my ability to navigate, yes he was.

did it make me think a lot more about it than previously, yes it did.

especially when I have been fogged in during rain, and couldn't see sh!t in the middle of the bay, and then could really see the point in understanding proper navigation skills, for just in case my gps failed.

has my gps failed before - yes it has. a button got stuck on because of a bit of salt getting into the button and the gps unit went into a fit, no more gps

[PinHead]

Spare hanheld garmin gps with c map card in it plus iphone with navonics app means I'll be doing fine without needing to use my compass n def wont be needing charts thats for sure, Its not called stupid its called well prepared. And if you dont belive that land is visible out that far then you must live somewhere down south where it aint worth being, 100km out from shute i can see the edward islands, hamo, whitsunday, hook, lindamin, hayman,120km out from able point can see bowen, glouster, double cones,80km out from lucinda can see palm group, hinschenbrook, if you cant see these then def get out of the way cause you'd be really struggling to use a compass in the swell. And jack seriously mate what r ya guna do really, I'm no hero ey but you'd def not enjoy that if thats how you'd start our conversation. My original reply was a joke but obviously none of you seen it in that light which tells me you prob all are sailors or victorians n need to be on a different forum so to continue on the path chosin Be damned if I'd be relying on charts n compass to get me through the reef up here at night, thats the time you anchor up n fish with a few beers then sleep, I trust nothing at night up here that I dont know like the back of my hand. And as far as being able to navigate without aids for my job I have to be able to navigate at night with no lights through rainforest n hills with a 35kg+ pack on using nothing but a map n compass and do it without sleep for 24hrs so I know how retardid you have got to be not to have a back up source of gps, why would any1 want to do it the hard way in this day and age.

so you use map and compass on land but don't on water...I would much rather trust a chart and compass than a GPS in an unknown stretch of water.

24 hours without sleep..that is the easy part.

going through the scrub like that just sounds like AJ crap.

[whiteman]

D river has a good point about fishing around the reefs. I use a chart for 1st time marks (entered into the GPS) to get me to the approximate point then use the sounder to navigate around bombies and mark spots as I go - then use these marks with confidence later. Charts up this way are far too low res unless you want to stay close to Townsville or Lucinda. And I fish around 80km from shore and can clearly see Hinchinbrook Island for reference for setting anchor, etc. It is very difficult to navigate by compass alone when you are getting bounced around in a tinny in the normal slop we get up this way. If the electronics cut out (and yes they have a couple of times in my boat) then line of sight with approx compass setting is the go. It hasn't happened at night or in a rain storm yet but then I will revert to the compass or the backup hand-held garmin. And I thought charts are mandatory for offshore?

My old mate who is a retired trout pro has never used electronic charts and doesn't need to as he's been well trained and has over 50 years of constant water time. Regardless, he's run into a few bits of coral over the years. I will NEVER get to his level if I live to be 1,000. Give me modern technology every time.

[theoldlegend]

true longitude represents time not distance...but if u take a line from point a to point b and take that measurement to the increments on the side of the chart it will give u the distance in nm of that line. it's important to measure the distance of that line with the increments directly across from its position on the chart as the increments actually change slightly between the top and bottom of the chart because of trying to project a round object onto flat paper!!!

We can blame a bloke called Gerhadus Mercator for that stuff. It's all his fault.

That wasn't his proper name though. His proper name was Gerhard Kremer and his other name was the Latin equivalent, and he preferred to be known by the Latin name.

He was born in 1512 and died on December 2, 1594, although I don't know what time on Dec 2 1594 he died. Probably not that important anyway, because he's been dead for 416 years and 29 days.

I wonder how many leap years are in the last 416 years? Now there's a little project if ever I saw one!

TOL

[Jarrah Jack]

My original reply was a joke but obviously none of you seen it in that light which tells me you prob all are sailors or victorians n need to be on a different forum so to continue on the path chosin

Was gunna say something about you having a go at sailors and Vics but when the quote came up with all those red lines that this spell check on firefox has I thought I'd give you a break.

[Roughasguts]

You can see land from 100km offshore??????????????? $hyte you must have good eyes. Been eating lotsa carrots have we??????

Idiot for using a compass at sea?????????????????? I aint even gonna comment on that one.

He he of course you can see 100km in front of you! ......if your at 10000 feet on a clear day. But with the curvature of the earth at sea level you be lucky to see 25 miles::)

[Fed]

Enter 12 Feet that will allow for 2 people @ 6 Feet tall each.
http://www.boatsafe.com/tools/horizon.htm

[whiteman]

He he of course you can see 100km in front of you! ......if your at 10000 feet on a clear day. But with the curvature of the earth at sea level you be lucky to see 25 miles::)
Is that nautical miles or imperial miles?

[whiteman]

Enter 12 Feet that will allow for 2 people @ 6 Feet tall each.
http://www.boatsafe.com/tools/horizon.htm
And the point is? Land up our way is a little bit higher than a few feet. The mountain behind my place is 3,500' high. Mt Bowen on Hinchinbrook Is is 3678'. Not hard to spot from some distance away.

[fisho64]

.. say, the fishing spot is 100k's offshore and traveling at 50kph ( average ) I'll get there in 2 hours.... tried to do that with knots and miles ????
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50 N miles @ 25 knots =2 hours, its the same calculation, just different measurements.

Where it get complex is I hear CONSTANTLY (I work at sea most of my life) radio stations etc (ABC often) reporting windspeeds as KPH. Usually as we have the BOM report onboard its easy to see that it reads knots and they read out kph. This is a (roughly) 100% error.
If you expect 40kmh winds when its actually 40 knot, you are likely in strife.
I have observed this for many years and amazingly it still goes on...

[D river]

In the weather we've had up here this year I'd like to see any1 get and follow a compass bearing at anymore than an idol, hell I cant even see the gps screen properly sometimes without staring at it for ages so I use land marks or a visual bearing I'll take earlier in ref to the sun to travel anysort of distance and It'd be impossible to have a chart rolled out and follow at 25-30knts Sorry 50-60kph and once on the reef its gps and ref off hinchenbrook the whole way or just polaroid sunny's. At night its all gps in that stuff and anything at pace is done on known plotted tracks. Have had the gps fail out there 1 time and it was no problem at all didnt need the handheld or iphone but was good to have it as a back up if we needed it but also didnt use the compas either just too easy to look at land and use it a a gide, if I cant see the island from there its only cause its under that big cloud thats p*ssing down rain on it so actually I can still see it and then about 20-30k out I can see the sugar jety thats 5km long and lit up like a chrisy tree at night. If the weather is that bad you cant see then you should of checked your weather properly before going out and shouldnt be driving in it anyway as boats dont show up on gps or charts and dont know about you but I cant afford a radar on AJ wages.

[Isaac]

Something dont add up there?? phil said fishing 100k's out? 100km = 53.996nm 50Km/h = 26.998 knots??

Sure can travel at 15 Knots, and travel 30 mile in 2 hours, but you'll be 24ish miles roughly from phil??

Unless yours was another example?

Cheers
Mitch

I used a different example Mitch

[Fed]

And the point is?
Only used the 12' as an example of boat to boat visibility whiteman and to show the heights could be added to conform to the single entry field in the link. Expected everyone to realise that any height could be entered, that's what the calculator is for.