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 » Online Classroom   » Inland and Coastal Navigation   » Public Discussion of Inland and Coastal Navigation   » 1210TR WB Prob 9-9 errata

Author Topic: 1210TR WB Prob 9-9 errata
 Marksail2 posted March 05, 2020 11:05 AM                   Gentlemen, In working through the exercises in the Navigation Workbook 1210 TR, Problem 9-9 specifically I think I found an error. The solution given was Set 053 T and 1.13 Drift. I don’t see how this can even remotely be correct. I’ve included MY solution clearly showing the Set to be 290 T and drift 1.29 kts over 2h10m giving an offset distance of 2.8 nm If I’m wrong please forgive me. If so I’d like to know how I miscalculated. Respectfully,Mark Starr From: Mark Starr
 David Burch posted March 05, 2020 11:08 AM                   Thanks. we will look into this. the solution did not show up. if it was a graphic (the only option to typing it out) has to be <800 px across and size <300 kb From: Starpath, Seattle, WA
 David Burch posted March 05, 2020 11:11 AM                   Mark, Toby said he got the solution directly from you to helpdesk, and he will post it for you. From: Starpath, Seattle, WA
 David Burch posted March 05, 2020 11:13 AM                   Here it is. From: Starpath, Seattle, WA
 Capt Steve Miller posted March 05, 2020 04:13 PM                   I worked the problem on the 1210TR chart. I found that the answer given at the end of the work book is correct at set is 54° and the drift is 1.13.Looking at your work I noticed that you were using a traveling time of 2 hours 10 minutes. When subtracting the starting time of 0915 from the end time of 1045 the elapsed time is 1 hour and 30 minutes. You traveled 9 nm not the 13 nm that you were using.Also, the True course is 90°, I do not know how you came up with 89.4°Hope this clears up the confusion. From: Starpath
 Marksail2 posted March 06, 2020 08:23 AM                   A rookie mistake for sure! One that NEEDS to be learned at the drafting board NOT the Navigation table! Taking the two times 1045-0915 = 130 which I saw as 2h 10m. If I had done it correctly I would have seen 1h30m which in turn threw my STD calcs way off! Goodness knows if I had done this at sea where I would be ??? LOL That's why I'm working through these exercises.BTW - again perhaps I'm wrong but my 1210TR chart shows a magnetic variation of 15degrees 15' W in the area of concern. Taking a 105M - 15.15 gives a heading of 89.45 degrees T That was my logic behind my solution. Was that in error?It is my hopes that others learn from my simple yet serious mistake!Wishing all calm seas and following winds!/\/\ark From: Mark Starr
 David Burch posted March 06, 2020 09:06 AM                   Usually in the introduction to our workbooks we state what variation should be used for the whole chart... to simplify things. Also as a practical matter it is difficult if not impossible to do any compass work better than ± 1º From: Starpath, Seattle, WA
 Marksail2 posted March 06, 2020 09:42 AM                   My corrected solutions From: Mark Starr
 Marksail2 posted March 06, 2020 09:42 AM                   From: Mark Starr
 Marksail2 posted March 06, 2020 09:54 AM                   Oops … arrow on graphic for current needs to be point TOWARD 54 degrees set. From: Mark Starr

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