Good point. As Sam has demonstrated, the methodology he used matches the distances in the Olympic log, and that speaks volumes, especially when the other method does not work out this way.
Why do you insist on posting erroneous information? Not until I sent you a private email explaining your error did you acknowledge it in your post of:Samuel Halpernosted Posted on Thursday, May 24, 2007 - 1:33 am:
Distance from Daunt's Rock to corner = 1504+173.6 = 1677.6 miles.
Samuel Halpern: Posted on Sunday, May 27, 2007 - 11:02 pm:
...if you take the data reported on Olympic's log for the distances the ship ran for the first three days and then add the distance from the third day's noon location to the corner you get the total that I gave above. ...
For the Titanic I got a distance to the corner of 1675, a number consistent with those distances to the corner for the Olympic taken from three separate voyages
I am amused by your armchair cohorts trying to support you. If Olympic or any ship runs 1680.4 nautical miles, and it is shown as 1677.6 miles that is incorrect. Also, if the course from off Kinsale is 256 degrees true, that is an error that puts the ship on a grounding course on Fastnet. When a distance is 131 nautical miles, fudging it to be 126 is incorrect.Samuel Halpern: Posted on Thursday, May 31, 2007 - 2:32 am:
Finally, the rhumb line distance from the noon position for June 18 to the corner is 173.6 nm. Total distance adds up to 1680.4 nm.
What I did is add up the distances reported in the log for the first three days to the noon position for June 18, which was 428+534+542=1504. I then added to that the 173.6 nm from noon to the corner to get 1504 + 173.6 = 1677.6 nm. The difference between the two methods is 2.8 nm.
In my post of May 31, 2007 - 2:32 am I was kind enough for the benefit of the readers (who I'm sure are quite amused by all of this by now) to explain to them how YOU were able to derived a distance of 1680.4 nautical miles.Sam, as a marine navigator you disappoint me. Believe me taking the data reported on Olympic's log for the distances the ship ran for the first three days and then add the distance from the third day's noon location to the corner you get the total = 1680.4 nautical miles.
The method I used to get the distance from Daunt's Rock to the corner made use of the run data from the log card itself. As I explained, I simply added up the distances reported in the log for the first three days to the noon position for June 18 (the 3rd day out), which was 428+534+542=1504. I then added to that the remaining 173.6 nm from noon to the corner to get 1504 + 173.6 = 1677.6 nm. It can't get much easier than that.What Capt. Collins did, using meridian parts calculations throughout, was to start from Daunt's Rock LV and go to a point south of the Old Head of Kinsale and then to a point 3 miles south of Fastnet Light. That gave him a distance of 56.1 nm. From there he took a rhumb line course (constant course angle) to the reported noon position for June 16, which by meridian parts calculation, is 372.3 nm. The total distance for the first day was given by adding these two distances together which gave 428.4 nm, which is close to the 428 nm written in the log card. The distance for the second day was given by taking a rhumb line from the noon position for June 16 to the noon position for June 17. That gave 535.7 nm by meridian parts calculation, compared to 534 nm that was written in the log. The next distance was given by taking a rhumb line from the noon position for June 17 to the noon position for June 18. This gave 542.7 nm by meridian parts calculation, compared to 542 nm written in the log. Finally, the rhumb line distance from the noon position for June 18 to the corner is 173.6 nm. Total distance adds up to 1680.4 nm.
Sam: I agree with you entirely. Although, we do not always agree, I do have the utmost respect for you and your ET posting.Your problem I'm afraid is not with me or the method I used. It is with the distance data in the abstract logs taken for Olympic's three westbound voyages in 1911 while she was on the southern route.
That is, also, a fault of too many deck officers, " the easy way"The method I used to get the distance from Daunt's Rock to the corner made use of the run data from the log card itself.... It can't get much easier than that.
What you failed to take into account Capt. Collins is the route the ship was following. Before 8 pm on June 18 they were following the great circle track toward the corner. A little before 8 pm they would have altered course to follow a rhumb line toward Nantucket LV. If you add the two separate distances you will see that they should get a noon-to-corner-to-noon distance that is close to the number entered on the log. I'm afraid you made a very basic mistake here by taking a direct rhumb line between those two noon positions.Example Log Card:
4th day (June 19th): day’s run 525? Mid lat distance is 501.16 nm.
Captain, this time I'm afraid, as a marine navigator, you have disappointed me...I'm afraid you made a very basic mistake here by taking a direct rhumb line between those two noon positions.
Many apologies for resurrecting such an old thread, but I was very interested to read this. Where can I find this information on Olympic's crossings? Is it available online, or in a book?The Olympic did not follow a single rhumb line course from one noon position to the next while on the great circle track to the corner. From detailed data that I looked at from several 1931 Olympic crossings, the logbook shows that they changed true course headings mostly about every 6 hours. (Sometimes as little as 5 hours or as much as 7 hours, but most changes appeared to be about every 6 hours or thereabouts.) This means they were changing course about every 3 degrees in longitude more or less. The distances between two noon positions along the GC track would therefore be less than the single rhumb line distance between the two noon positions because they tried to follow the great circle track fairly closely, more so than what I expected they would do. I believe this is why the distances recorded on those three log cards consistently resulted in a somewhat shorter distance to the corner than what those straight rhumb line distances would give.
Neither. It was shown to me from a private source. The data came from compass course books that were kept. In the 1930s they were using a gyro compass to steer by, thus the ship would steer true courses. But they also recorded the magnetic headings in the columns for the steering and standard magnetic compasses and as well as their deviation errors.Where can I find this information on Olympic's crossings? Is it available online, or in a book?