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Boat Forum / Sailing / September 2008Distance question
Apologies if it's been done already but I can't find the answer. What's the furthest distance you can sail in a straight line (great circle)? Cheers. > Apologies if it's been done already but I can't find the answer. > What's the furthest distance you can sail in a straight line (great > circle)? > > Cheers. How can a straight line be a great circle? You could sail the Southern Ocean at a latittude which takes you south of Cape Horn ad infinitum so long as you can avoid the icebergs. Dennis. >> Apologies if it's been done already but I can't find the answer. >> What's the furthest distance you can sail in a straight line (great [quoted text clipped - 5 lines] > Ocean at a latittude which takes you south of Cape Horn ad infinitum so > long as you can avoid the icebergs. I should add that if you are really sailing, not motoring, the question is unanswerable as the wind direction changes dramatically every so often! Dennis > Dennis. >> Apologies if it's been done already but I can't find the answer. >> What's the furthest distance you can sail in a straight line (great >> circle)? >> > How can a straight line be a great circle? Er, because a great circle route is a er straight line. It's the shortest route between two points on a globe. >You could sail the Southern Ocean at a latittude which takes you south of >Cape Horn ad infinitum so long as you can avoid the icebergs. Well no, that might give you a constant heading on the compass but your track if you could see it would be a steady curve to port or starboard. Tim w > Apologies if it's been done already but I can't find the answer. > What's the furthest distance you can sail in a straight line (great > circle)? About 10,000 miles at a guess either N-S in Atlantic or Pacific, starting and ending in the ice. Off course if the artic melts you can probably get to 20,000 miles. :) >> Apologies if it's been done already but I can't find the answer. >> What's the furthest distance you can sail in a straight line (great [quoted text clipped - 3 lines] > starting and ending in the ice. Off course if the artic melts you can > probably get to 20,000 miles. :) It looks like you should be able to sail from California, or somewhere in Central America, head off at about 225 degrees, pass under NZ and Oz, miss Antarctica, and come back north hitting Africa somewhere... it may be that if you start further south, with a more westerly heading, you may miss Africa and manage to cross the Atlantic too. I really need a globe and a piece of string, working this out on Google Earth isn't that easy. What the total distance would be, I have no idea. And how you'd manage to keep a straight line, when you've "gone round the bottom" and are heading more north again... how would you know what your heading should be? Could this be the only sailing feat not yet to have been achieved? Neil, when you decide the set off, let me know, I'd like to follow your progress. :) Justin.  SignatureJustin C, by the sea. > Apologies if it's been done already but I can't find the answer. > What's the furthest distance you can sail in a straight line (great > circle)? > > Cheers. You can sail in a straight line for the rest of your life at latitude 55 to about 63 south. No land masses between those latitudes. You can just go round and round and round. Prevailing westerlies to boot. http://encarta.msn.com/map_701516656/South_Pole.html (zoom all the way to minus) I've done it three or four times around in my Swan 60 just to be able to say I did it. But, I wouldn't recommend it. Very cold and too many icebergs. Wilbur Hubbard Not an answer to the question, but interesting trivia, I understand the record for the longest single tack is 2,300 nautical miles on port tack. >> Apologies if it's been done already but I can't find the answer. >> What's the furthest distance you can sail in a straight line (great >> circle)? > > You can sail in a straight line...[...] > ... just go round and round and round. [...] Something wrong there. Tim w Wilbur Hubbard wrote: >> Apologies if it's been done already but I can't find the answer. >> What's the furthest distance you can sail in a straight line (great [quoted text clipped - 4 lines] > You can sail in a straight line for the rest of your life at latitude 55 to > about 63 south. Yes, of course, but a constant direction course (you're implying straight east or straight west, right?) is no great circle course except east/west at latitude 0. Regards, -is Signatureseal your e-mail: http://www.gnupg.org/ On Sep 1, 7:18 am, "Wilbur Hubbard" <wilburhubb...@thefarm.invalid> wrote: > > Apologies if it's been done already but I can't find the answer. > > What's the furthest distance you can sail in a straight line (great [quoted text clipped - 11 lines] > > Wilbur Hubbard Wilbur, you can't. That's a curve. >Apologies if it's been done already but I can't find the answer. >What's the furthest distance you can sail in a straight line (great >circle)? > >Cheers. It depends on how many times you go round! A great circle will take you back where you came from, eventually. If you mean "How far can I sail without hitting land", I don't know but I'd guess you can manage at least half the circumference of the world; that is about 20,000 km. The Pacific is awfully big! Paul >> Apologies if it's been done already but I can't find the answer. >> What's the furthest distance you can sail in a straight line (great [quoted text clipped - 10 lines] > > Paul MicroSoft Street and Trips program lets you enter two points and then will show a great circle path between the two. Vietnam to Ecuador is about 11200 miles of water. And 14N 128W to 15N 54E gives me about 12200 miles just skimming the antartic. I think I could go further but the program wants to give me the least distance and therefore flips and goes the other way. It looks like Baja to Sudan might be the longest possible route. Maybe 14000 or 15000 miles. hpeer wrote: >>> Apologies if it's been done already but I can't find the answer. >>> What's the furthest distance you can sail in a straight line (great [quoted text clipped - 14 lines] > > Vietnam to Ecuador is about 11200 miles of water. Water miles or land miles? -is > hpeer wrote: >>> [quoted text clipped - 19 lines] > > -is MicroSoft Streets and Trips = statute miles, not nautical miles hpeer wrote: > MicroSoft Street and Trips program lets you enter two points and then > will show a great circle path between the two. [quoted text clipped - 4 lines] > antartic. I think I could go further but the program wants to give me > the least distance and therefore flips and goes the other way. Just subtract the distance it tells you from the Earth's circumference. For a quick start, assume a spherical earth with radius of 6371 km. For a very rough sketch, assume the original French revolutionary definition of the km as 1/40000 of the earth's circumference, or the rough definition of a nautical mile as 1/21600 of the earth's circumference. > It looks > like Baja to Sudan might be the longest possible route. Maybe 14000 or > 15000 miles. If you want to compute the distances yourself: it's r * g (expressed in radians) where cos(g) = sin(latA) * sin(latB) + cos(latA) * cos(latB)*cos(longB - longA) Regards, -is Signatureseal your e-mail: http://www.gnupg.org/ On Sep 3, 4:02 pm, Ignatios Souvatzis <u502...@beverly.kleinbus.org> wrote: > > MicroSoft Street and Trips program lets you enter two points and then > > will show a great circle path between the two. [quoted text clipped - 7 lines] > Just subtract the distance it tells you from the Earth's circumference. > For a quick start, assume a spherical earth with radius of 6371 km. You can't do that on Google Earth, as once you pass the half way mark you have no accurate way of knowing whether you are maintaining course on the same great circle. Paul {Hamilton Rooney} wrote: > On Sep 3, 4:02 pm, Ignatios Souvatzis <u502...@beverly.kleinbus.org> > wrote: >> Just subtract the distance it tells you from the Earth's circumference. >> For a quick start, assume a spherical earth with radius of 6371 km. > > You can't do that on Google Earth, as once you pass the half way mark > you have no accurate way of knowing whether you are maintaining course > on the same great circle. Err... I think I see - so while you can compute the long way between two points on coasts of the Pacific, you don't know whether they hit some land in between... too bad. We must get an old-fashioned globe, then. -is Signatureseal your e-mail: http://www.gnupg.org/ On Sep 3, 7:33 pm, Ignatios Souvatzis <u502...@beverly.kleinbus.org> wrote: > > On Sep 3, 4:02 pm, Ignatios Souvatzis <u502...@beverly.kleinbus.org> > > wrote: [quoted text clipped - 14 lines] > -- > seal your e-mail:http://www.gnupg.org/ If you play around with Google Earth you'll see it more clearly. Possibly 18000 miles plus, but I can't be sure if it hits land - from Pakistan to Siberia, via Cape Horn (keeping west of Madagascar). >Paul {Hamilton Rooney} wrote: >> On Sep 3, 4:02 pm, Ignatios Souvatzis <u502...@beverly.kleinbus.org> [quoted text clipped - 12 lines] > >We must get an old-fashioned globe, then. or a boat? SignatureMartin Martin wrote: >>(...) We must get an old-fashioned globe, then. > > or a boat? Alas, my boat isn't suitable for ocean trips. -is Signatureseal your e-mail: http://www.gnupg.org/ On Sep 4, 2:48 pm, Ignatios Souvatzis <u502...@beverly.kleinbus.org> wrote: > >>(...) We must get an old-fashioned globe, then. > > > or a boat? > > Alas, my boat isn't suitable for ocean trips. Alas, even if it were, it wouldn't help to answer the question. It requires a globe, not a boat! >On Sep 4, 2:48 pm, Ignatios Souvatzis <u502...@beverly.kleinbus.org> >wrote: [quoted text clipped - 6 lines] >Alas, even if it were, it wouldn't help to answer the question. It >requires a globe, not a boat! Not having an accurate globe didn't stop Magellan :o) SignatureMartin > On Thu, 4 Sep 2008 02:35:49 -0700 (PDT), "Paul {Hamilton Rooney}" > [quoted text clipped - 14 lines] > > Martin But he didn't know where he was going, and when he got there he didn't know where he was, and when he returned he didn't know where he'd been! But more seriously - he couldn't know whether he was sailing in a straight line unless it was N-S or along the equator. Now we have it cracked - computers and GPS. >> On Thu, 4 Sep 2008 02:35:49 -0700 (PDT), "Paul {Hamilton Rooney}" >> [quoted text clipped - 18 lines] >know where he was, and when he returned he didn't know where he'd >been! but he had got himself "an old-fashioned globe" :o) >But more seriously - he couldn't know whether he was sailing in a >straight line unless it was N-S or along the equator. >Now we have it cracked - computers and GPS. SignatureMartin > On Thu, 4 Sep 2008 03:19:04 -0700 (PDT), "Paul {Hamilton Rooney}" > [quoted text clipped - 33 lines] > > - Show quoted text - Yes, but he still couldn't do the straight line thing! AFAIK it's not possible by traditional navigation methods - except in the special circumstances already mentioned. I am willing to be corrected, of course. On 4 Sep, 18:25, Martin <m...@address.invalid> wrote: Yes, but he still couldn't do the straight line thing! AFAIK it's not possible by traditional navigation methods - except in the special circumstances already mentioned. I am willing to be corrected, of course. Navigators absolutely did sail great circle routes by traditional methods. You have to change your heading as you go along but calculating a compass course for a great circle route every day or every watch was one of the standard navigation skills. Tim w > On 4 Sep, 18:25, Martin <m...@address.invalid> wrote: > [quoted text clipped - 9 lines] > > Tim w Well, almost. Didn't that involve lots of small deviations from the great circle? You couldn't change course every second - but following a computerised course allows you to do that and more. >On 4 Sep, 18:25, Martin <m...@address.invalid> wrote: > [quoted text clipped - 7 lines] >course for a great circle route every day or every watch was one of the >standard navigation skills. Also done by airline pilots at one time. SignatureMartin > >On 4 Sep, 18:25, Martin <m...@address.invalid> wrote: > [quoted text clipped - 12 lines] > > Martin Not exactly - they did a succession of curves, approximating to a straight line. >Yes, but he still couldn't do the straight line thing! AFAIK it's not >possible by traditional navigation methods - except in the special >circumstances already mentioned. I am willing to be corrected, of >course. We still can't do the straight line thing. We haven't yet built a boat that can sail in a straight line across the Solent, never mind half way round the world. -- Alastair We have evidence that on Thu, 04 Sep 2008 03:19:04 -0700, Paul {Hamilton Rooney} wrote: >> On Thu, 4 Sep 2008 02:35:49 -0700 (PDT), "Paul {Hamilton Rooney}" >> [quoted text clipped - 16 lines] > But he didn't know where he was going, and when he got there he didn't > know where he was, and when he returned he didn't know where he'd been! Bzzzzt. He didn't return. > But more seriously - he couldn't know whether he was sailing in a straight > line unless it was N-S or along the equator. Now we have it cracked - > computers and GPS. SignatureDick Georgeson Whenever you find that you are on the side of the majority, it is time to reform. -- Mark Twain > We have evidence that on Thu, 04 Sep 2008 03:19:04 -0700, Paul {Hamilton > [quoted text clipped - 21 lines] > > Bzzzzt. He didn't return. I didn't know that. I've just been reading it up. Thanks for the correction. Martin wrote: >>On Sep 4, 2:48 pm, Ignatios Souvatzis <u502...@beverly.kleinbus.org> >>wrote: [quoted text clipped - 8 lines] > > Not having an accurate globe didn't stop Magellan :o) Yeah, but he didn't sail the longest great circle course, either. -is Signatureseal your e-mail: http://www.gnupg.org/ On Sep 4, 6:28 pm, Ignatios Souvatzis <u502...@beverly.kleinbus.org> wrote: > >>On Sep 4, 2:48 pm, Ignatios Souvatzis <u502...@beverly.kleinbus.org> > >>wrote: [quoted text clipped - 10 lines] > > Yeah, but he didn't sail the longest great circle course, either. We don't know what that course is! -- Neil Barker > On Sat, 30 Aug 2008 04:26:43 -0700 (PDT), Neil Barker > [quoted text clipped - 7 lines] > It depends on how many times you go round! A great circle will take > you back where you came from, eventually. Can you sail over the land? On Sep 1, 7:12 pm, Paul Cooper <paul.coo...@invalid.bas.ac.uk> wrote: > On Sat, 30 Aug 2008 04:26:43 -0700 (PDT), Neil Barker > [quoted text clipped - 7 lines] > It depends on how many times you go round! A great circle will take > you back where you came from, eventually. Can you sail over the land? He meant sailing east or west from a point south of Cape Horn. No land there, just the Southern Ocean. Dennis. > On Sep 1, 7:12 pm, Paul Cooper <paul.coo...@invalid.bas.ac.uk> wrote: > [quoted text clipped - 16 lines] > > Dennis. He asked whether the question referred to how far you can sail without hitting land. >> "Paul {Hamilton Rooney}" <PaulVRoo...@gmail.com> wrote in messagenews:9e18d684-61ed-429d-8064-89ff578ada6e@s9g2000prg.googlegroups.com... >> On Sep 1, 7:12 pm, Paul Cooper <paul.coo...@invalid.bas.ac.uk> wrote: >> [quoted text clipped - 19 lines] > He asked whether the question referred to how far you can sail without > hitting land. If the route involves the southern oceans then allowance must be made for the ice of the Antartic, which spreads surprising far north. I know of somebody who was criusing the S Atlantic (Argentina, Falkland Islands, South Georgia and onward to Cape Town). He left S Georgia Late April (start of autumn down there), at 54 deg S, and for the first few nights had to heave too because of the risk of bumping into icebergs. >>> "Paul {Hamilton Rooney}" <PaulVRoo...@gmail.com> wrote in >>> [quoted text clipped - 25 lines] >If the route involves the southern oceans then allowance must be made for >the ice of the Antartic, which spreads surprising far north. Antarctic! >I know of somebody who was criusing the S Atlantic (Argentina, Falkland >Islands, South Georgia and onward to Cape Town). He left S Georgia Late >April (start of autumn down there), at 54 deg S, and for the first few >nights had to heave too because of the risk of bumping into icebergs. He would never have had that problem on/with the Norfolk Broads. :o) SignatureMartin >>If the route involves the southern oceans then allowance must be made for >>the ice of the Antartic, which spreads surprising far north. > > Antarctic! Nah, he's referring to them naffin' great trucks they have down there ;-) >>I know of somebody who was criusing the S Atlantic (Argentina, Falkland >>Islands, South Georgia and onward to Cape Town). He left S Georgia Late >>April (start of autumn down there), at 54 deg S, and for the first few >>nights had to heave too because of the risk of bumping into icebergs. > > He would never have had that problem on/with the Norfolk Broads. :o) 'Scuse me, I've had to break the ice to get out of my dyke and onto the broad before now. I took two Norweigian students sailing one February, I was dressed in full survival gear and they had a T-shirt on under their jackets. They said it was quite a warm day for February, in fact they threatened to take their coats off if it got up to zero degrees. The ice was a good quarter of an inch thick, my Vivacity was rising up on it then breaking through. TonyB >>>If the route involves the southern oceans then allowance must be made for >>>the ice of the Antartic, which spreads surprising far north. [quoted text clipped - 20 lines] >ice was a good quarter of an inch thick, my Vivacity was rising up on it >then breaking through. You are lucky you didn't cut your boat in half along the water line :o) I had something similar in NL, when a lake froze one February when we were about 3 miles from our destination. I did have visions of being frozen into the ice. SignatureMartin >On Sep 1, 7:12 pm, Paul Cooper <paul.coo...@invalid.bas.ac.uk> wrote: >> On Sat, 30 Aug 2008 04:26:43 -0700 (PDT), Neil Barker [quoted text clipped - 15 lines] > >Dennis. Sometimes it worries me, the number of people on this forum that don't appear to know what a 'great circle' is. (But sometimes it doesn't) -- Alastair > On Wed, 3 Sep 2008 09:25:50 +0100, "Dennis Pogson" > [quoted text clipped - 22 lines] > Sometimes it worries me, the number of people on this forum that don't > appear to know what a 'great circle' is. (But sometimes it doesn't) Well, the navigation skills of someone who thinks that you can pick any line of latitude and sail along it in a straight line are rather worrying. But there's sailing and then there's sailing..... >>On Sep 1, 7:12 pm, Paul Cooper <paul.coo...@invalid.bas.ac.uk> wrote: >>> On Sat, 30 Aug 2008 04:26:43 -0700 (PDT), Neil Barker [quoted text clipped - 21 lines] > -- > Alastair My old monochrome laptop, circa 1990, had a programme which calculated a Great Circle route from anywhere to anywhere on earth, in fact I still have it somewhere on my recent PC's. You simply enter the Lat/Lon of your start and destination, then for each longitude you enter it gives you a latitude to aim for, plus a course to said latitude. Old trig, uses "have" functions (1-cos/2). Easy to use if that is your poison. Don't find it necessary to use it on the West Coast as my eyes seem to work OK, and anyway any old GPS will give you the GCC to any waypoint, won't it? Dennis. Dennis. >> On Sat, 30 Aug 2008 04:26:43 -0700 (PDT), Neil Barker >> [quoted text clipped - 9 lines] > >Can you sail over the land? with a land yacht? SignatureMartin |
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