Navigation really has only one requirement: predict the future course (and sometimes speed) of a vessel endeavoring to reach a specific destination. There is no other purpose for navigation in the life of a ship other than determining how to get where it's going. We should not confuse the data necessary to perform that predictive function with the actual purpose of the exercise. In 1912 it was impossible for a navigator to know the course to a destination without knowing the ships location first. That is, even Joseph Boxhall with his nav training could not find his way anywhere if he did not know the latitude and longitude of his starting point. Dropped in the middle of an ocean, he would have been lost despite all of the accouterments of a navigator. (Today, the GPS system “knows” where the satellites are, so can find a lost navigator, but that was in the future beyond Boxhall’s lifetime in 1912.) So, there was an absolute need to know at all times the answer to the question, “Where am I?”
Surprisingly, for the importance of the "where am I?" question to under way navigators (prior to GPS) those working in 1912 chartrooms almost never knew exactly where they were. The best they could do is calculate where they probably were a few minutes or hours ago. The one exception was taking departure at the very start of a voyage when the time a ship passed a known landmark gave an accurate “real time” fix. After that, everything was an approximation. Even star sights did not fix the ship where it was, but at best approximately where it was. A round of celestial sights took time, so the first sight of a series was customarily “advanced” to the time of the last. Then, the computations began. It might be minutes or hours before the whole set of sights was reduced to a position somewhere behind the ship.
To keep as tight a handle on “where am I?” as possible, dead reckoning was employed between fixes. This is a sort of human-powered inertial navigation system. It is based on predicted speed and predicted direction from the last fix. The trouble is that ships don’t always go as fast as they should or in the direction they are heading. Currents and windage play havoc with dead reckoning. This is why dead reckoning was (and continues to be) discontinuous. The navigator plots carefully from one fix to the next, but knowing the DR track line is never accurate. It always produces a DR position in error some distance from the better position obtained by the next fix. What happens then? Well, the navigator forgets everything that he has done and starts over again with the new fix as the origin for a new DR plot.
This discontinuous nature of dead reckoning due to its built-in errors must be accounted for in trying to recreate the ship's track from Daunt Rock or anywhere else. The ship's DR would have been restarted several times daily depending upon the availability of star sights. Had a graphical track line been kept in Titanic, it would not be a smooth, continuous pencil line from start to wreck. Rather, it would be a series of discontinuous lines, each one originating at a fix but terminating in open ocean some distance from the next fix.
However, no such track line exists because in 1912 they did not plot course lines on a chart as we do today. DR positions were created entirely through a set of mathematical processes usually lumped together (not quite correctly) as "The Sailings." Latitude and longitude were determined directly without charts, protractors, and parallel rulers. A disadvantage of this system is that it deprived the navigator of a graphic representation of the ship’s progress. Often, this visualization makes navigational errors more obvious than if pure numbers are presented as tiny pencil crosses on a chart.
There is no doubt in my mind that Sam is correct about much of the "navigation" put into the record by the various officers. A lot of things appear to have been ex post facto creations to smooth over troublesome areas in the story. I fear that Sam is making the same mistake on the chart he presented. But, before Sam and I start to cross dividers, the plot he presented is the same as I was drawing until about six months ago. It was only then that I realized that traditional re-creations of Titanic’s dead reckoning do not take into account the single most important set of coordinates; nor do traditional forensic plots begin with the concept that navigation is predictive, not historic in its nature.
The key piece of information missing from Sam's plot and from the plots that I was doing is the first set of CQD coordinates. Titanic sent two different locations, not one. Boxhall's famous set was the second. But, the ignored first set of coordinates given by Captain Smith to the Marconi operators, 41 44 N; 50 24 W, is the more critical to understanding of what took place.
Make no mistake, both sets of coordinates are "incorrect" with regard to the actual location of the wreck. But, that conclusion hides the truth. Neither one was meant to be the location of the ship, but rather both were predictions of where Titanic "ought to be" at some specific time that night. To understand the two sets of CQD coordinates you must understand what the navigators who created them were predicting. To my mind, the longitude of the first set of coordinates from Captain Smith strongly indicate it was a prediction of the ship’s midnight position. The second set by Boxhall was a prediction of where Titanic should have been 20 minutes earlier at the 11:40 p.m. time of the accident.
I have come to believe the two CQD coordinates are separated by the element of time. Specifically by 3/10ths of an hour or 18 to 20 minutes.
An axiom in navigation is that two locations separated by time for the same object represent a line of position. That is, if Titanic were to have ever been at those two locations at times separated by about 20 minutes, it could have done so only by steaming in a straight line from one to the other. Like it or not, the two CQD positions tell us that the men who created them thought Titanic was on a course from Boxhall's 41 46 N; 50 14 W to Smith’s 41 44 N; 50 24 W.
The direction of travel contained within the two CQD coordinates is near enough to 255 degrees to make no difference. The distance on my plot between the two coordinates is about 7.3 miles, which in 20 minutes requires 22 knots--exactly the speed Boxhall said Titanic was making turns for at the time of the accident.
So, using evidence in the form of the two undisputed sets of CQD coordinates, it appears that Smith and Boxhall thought the ship was steaming on a 255 course at 22 knots. The speed fits the historical record of Boxhall’s testimony. But, why 255 degrees? That was not the course to New York.
To answer that question we have to ask another one. What was the proper course to North America? I believe it was about 266.5 degrees from "The Corner." Simple subtraction shows the 255 degree line between the CQD coordinates is about 11.5 degrees different from the proper course. Anyone with “old school” navigational experience should not have bells going off in his head. 11.5 degrees is essentially one compass point. And, in 1912 it was still customary to give steering orders in points, not degrees as we do today.
If we take the line of position back to where it crosses the 266.5 track line, what does that tell us? Well, at 22 knots this crossing lies 5:40 from "The Corner." Quartermaster Rowe said the ship turned "The Corner" at 1745. The officers spoke of 1750 or 1755. Taking the middle number, 1750, and adding 5:40 to it gives a time for the crossing of 2330 hours ATS, or 11:30 p.m. in everyday speech.
So, using the historical record we have found that the two CQD positions when put into context with the ship's course and speed from "The Corner" indicate something momentous: Titanic changed course one point to the south at 11:30 p.m. ATS.
NO, this course change did not result in the accident. Or, at least it did not directly cause the accident. The importance of this revelation is that it shows Titanic under Captain Smith did not go steaming pall mall into an ice field. The evidence that has been on the record for almost a century shows a completely different story from the slanderous account of a sleepy captain letting his ship speed headlong to its doom.
Turning one point to the south at 11:30 p.m. ATS shows a prudent Captain Smith taking an active hand in the safe conduct of the voyage. He was intended to take his ship around the southern end of the ice field. Such an action ties in perfectly with Boxhall's testimony about the captain doing a lot of plotting during the hours leading up to the accident. Smith did not plot ice for the enjoyment of making tiny “X” marks on the chart. He was trying to predict the safe way through the ice danger while at the same time keeping the voyage as short as possible. (Remember, his boss Ismay wanted a fast trip.)
Why an 11:30 p.m. course change? Well, because of the requirement to check the steering compass against the standard compass every half hour. The most efficient time to make a course change would have been when an officer had to go to the compass platform anyway. Hence, 11:30 p.m. allowed the course change and compass check to be combined for convenience.
Now the question remains, "Why the westerly error in the two CQD positions?"
Sam and I both know that is a matter of time.
-- David G. Brown