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» Online Classroom   »   » Public Discussion of Cel Nav   » HBS July 4-5 logbook question

Author Topic: HBS July 4-5 logbook question
Rich A

 - posted March 18, 2017 03:53 AM      Profile for Rich A           Edit/Delete Post 
Can't believe I'm already asking questions, but here we go.

pg. 8 Log entry #4 (WT 1609) to Log entry #5 (WT 0000) = 7hrs51min (or 55 nm @ 7 knots).

pg. 76 shows the distance between DR 1609 and DR 0000 to be only 35 nm, instead of the calculated 55 nm.

Is there a reason for this? It would seem that starting my trip off with a 20 nm error might be a flawed strategy. Please advise.

From: Lacey
David Burch

 - posted March 19, 2017 03:49 PM      Profile for David Burch           Edit/Delete Post 
Thanks. I will check this.

The 00z positions shown along the route are all "artificial," in that these were not real logbook points; they were added by DR at the time we made the book to make it easier to see where the dates changed, which in principle would make interpreting the plots easier.... assuming they are right!

Their location on the plots (ie the 00z points) should not really affect the results of the fixes, but we need to track your question down to resolve this.

From: Starpath, Seattle, WA
Rich A

 - posted March 19, 2017 06:16 PM      Profile for Rich A           Edit/Delete Post 
Ok got it. The distance from WT1609 to WT0504 = 90 nm, which plots correctly. If the WT0000's are just generic reference points, then it makes sense now. Thanks.


From: Lacey
David Burch

 - posted March 19, 2017 07:11 PM      Profile for David Burch           Edit/Delete Post 
OK. thanks. we are still going to check where the 0000 point should be and try to see why it got plotted wrong.

then when we resolve this we will add an errata.

thanks for pointing this out.

From: Starpath, Seattle, WA
David Burch

 - posted March 20, 2017 01:20 AM      Profile for David Burch           Edit/Delete Post 
the plotted 0000z position on page 76 and 77 is wrong. the 00z DR is 46° 55.7’N 127° 13.7’W'

I went to post this in the errata, but it was already there.


Please check that to see a couple other points that might show up.

From: Starpath, Seattle, WA

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