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Old 19-11-2013, 05:43   #61
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Re: CTS vs Following Rhumb Line - DILUTED THREAD

Originally Posted by Dockhead View Post
I think that in general this is right, and that it is am important insight.

The only thing I would say is that SWL's method is inherently more accurate, and is no more trouble than the traditional method, so the accuracy is without any cost. Therefore, I am convinced that it is superior.

Another thing I would say based on experience -- although they are on the one hand too precise, as variations speed and steering accuracy and wind direction will inevitably conspire to mess them up, at the same time, none of these methods is actually precise enough, because they don't consider the fact that the currents are not precisely perpendicular (and deviations of current direction have a big effect on the results), and because they use coarse-grained current data from tidal atlases.

When I realized all of that, I just stopped doing it by hand altogether and started using a computer, which has been vastly better, not too mention easier.

Using a computer, you deal with unexpected changes in wind or boat speed by rerunning the numbers every couple of hours, which only takes a few seconds. It works a treat; I'll never go back.

The computer also deals brilliantly with the situation which is impossible to do by hand -- strong rotary currents like in the Channel Islands.

I would contend you are inverting the meaning the accuracy and precision. SLs method is demonstratively more precise as it deals more correctly with partial tides etc. However accuracy may only be determined by comparing it with a better "standard" for example you computer program, which presumably has access to small quantum's of tide data. ( ultimately at infinitely small tidal quantums , both RYA and SLs methods coincide )

The same way I can empirically compare the "precision" of my different multimeters , but I need a calibration standard ( thats better then my multimeters) to actually confirm the "accuracy"

SLs methods have definite ease of use advantages in certain circumstances , Ill not argue that


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Old 19-11-2013, 05:49   #62
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Re: CTS vs Following Rhumb Line - DILUTED THREAD

Originally Posted by foolishsailor View Post

...but who has one of those...
Well - ahem, yes - some do

Bit of a bother to program it

I must go down to the seas again, to the lonely sea and the sky,
And all I ask is a tall ship and a star to steer her by
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