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Author
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Topic: Cel Nev on the Great Lakes(Inland Seas)
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Attila
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posted August 08, 2014 11:30 AM
Just wondering what additional steps needed if any, when we are on the great lakes? How does the (Hs) sextant angle changes when we are let say on lake Erie where we are at 173.9 m above mean sea level? We'll still have to count for the dip correction, also for the Index Correction (IC), I just feel there has to be an additional step to count for the difference in mean sea levels.
I have so many questions, but hope you can help me with dis one. Thank you for your time.
Attila.
From: Ontario
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David Burch
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posted August 08, 2014 11:37 AM
No special corrections needed as long as you are looking at the horizon that is far enough away... i.e. more than say 1.5 nmi x square root of (height of eye in ft).
if the horizon is closer than that, then you will need to use dip short instead of the regular dip table. The dip short corrections are covered in depth in our textbook.
From: Starpath, Seattle, WA
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Attila
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posted August 08, 2014 12:53 PM
Pg 147, thank you for that. So as long as I have a horizon over 1.5 nm no special correction needed ,or if the distance to the horizon D in nm is greater than square root of HE in feet. This is exactly the answer I was looking for. Thank you.
From: Ontario
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David Burch
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posted August 08, 2014 01:46 PM
sorry... the distance off must be greater than 1.5 times the square root of eye ht in feet. i.e. if you are standing at 7 ft above water line, then you must be 1.5 x sqrt(7) = 1.5 x 2.65, which is about 4 nmi off.
From: Starpath, Seattle, WA
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Attila
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posted August 08, 2014 03:18 PM
in the textbook, it only says that as long as D in nautical miles is greater than the square root of HE, no special corrections are needed. I could not fined the formula, you have given me in the textbook, only the formula to calculate "Dip Short".
From: Ontario
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David Burch
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posted August 08, 2014 03:46 PM
I have simply added a bit of safety to the formula in the book. i.e. you might be able to get closer to shore and not have to use dip short.
you will discover this as you apply the method. i.e. if D is far enough or H low enough, you will see that dip short is the same as dip from Nautical almanac.
From: Starpath, Seattle, WA
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Attila
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posted August 08, 2014 04:06 PM
Thank you for taking the time to explain and clarify this topic.
From: Ontario
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