I would/do use the gnomonic chart method. Using pure calculations and not plotting the rhumblines on a chart runs the risk of sailing over something you don't want to sail over.
Gaz
__________________
There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
You can use pure calculations for the Great Circle routing as long as you plot the results on the mercator charts. Thus you can see if you need to truncate the route or not.
We would use general charts and plot the Great Circle Course for every five degrees across the Pacific Ocean. This works quite well for my navigation.
It doesn't matter what kind of chart you plot the results of your calculations on as long as the dangers are marked. It is easier on a mercator because rhumb lines are straight and you can draw them with a ruler.
Gaz
__________________
There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
It depends on what the projection of the plotting sheet is. If it is a mercator projection you should see a series of rhumb lines approximating a curve. If it is a gnomonic chart you should get a straight line.
Plotting sheets are normally mercator sheets.
Short answer - yes.
Gaz
__________________
There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
I've never seen a gnomonic chart of a scale suitable for plotting points and then transferring to a plotting sheet, for a transoceanic passage. My advise is to calculate your Great Circle via nav. calculator or h.o. 229 for changes of course every 5 degrees of longitude and, once you go off your coastal chart, plott them on a small scale plotting sheet. You're unlikely to encounter any obstructions where using a G.C. is advantageous.
__________________ The brain is merely a knot that keeps the spinal cord from unraveling.
You're unlikely to encounter any obstructions where using a G.C. is advantageous.
Just don't use the hurricane tracking mercator chart of the North Atlantic, like the skipper of this J-boat did. His GCR took him right over Sable Island, which wasn't on the chart:
Sable Island is not a good place... basically a ship's graveyard in the North Atlantic.
__________________
Sailingdog Telstar 28
New England
You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.
—Cpt. Mal Reynolds, Serenity (edited)
If you're new to the Sailnet Forums... please read this POST.
I've never seen a gnomonic chart of a scale suitable for plotting points and then transferring to a plotting sheet, for a transoceanic passage. My advise is to calculate your Great Circle via nav. calculator or h.o. 229 for changes of course every 5 degrees of longitude and, once you go off your coastal chart, plott them on a small scale plotting sheet. You're unlikely to encounter any obstructions where using a G.C. is advantageous.
Here is a link to Admiralty Charts for plotting Great Circles: http://www.sailgb.com/p/admiralty_ch..._gnomonic_135/
The idea is you just draw a straight line between the start and the end of your great circle route and pull the waypoints off it and plot them on a navigation chart.
As for obstructions, suit yourself.
__________________
There is a tide in the affairs of men,
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
Shakespeare, Julius Caesar IV, iii, 217
Great circle/rhumb line
Linear Mode
