I can offer the following:One thing I do agree with Dave about is that there can only be one standard compass. It is the standard to which other compasses aboard are adjusted. There are a number of things I want to set forth as what I understand. If I am wrong then I welcome correction:
1. I can possibly understand the designation of a standard compass on the wheelhouse roof of Olympic which would render the midship compass to an unknown role.
2. What I can't understand is that while the change in compass locations on Olympic was a retrofit, the same cannot be said of Britannic.
3.While Britannic was being planned for mercantile service, her Specification Book lists both a wheelhouse roof compass and a midship compass.
4. This Britannic compass configuration can be confirmed by photos of HMHS Britannic.
5. It is obvious that the wheelhouse roof placement of a standard compass would be more convenient.
6. It is most likely that the midship standard compass location would have the least magnetic interference.
These observations still don't explain why if the wheelhouse roof compass was the standard compass then what purpose would the midship compass serve? The opposite statement would also hold true. Attached are two entries in the Britannic Specification Book. The one specifies all compasses aboard but does not designate which would be the standard compass. Another interesting side note is the description of the midship compass platform. In the Shipbuilder journal for Olympic it describes the compass platform as "brasswork". In the Britannic Specification Book the compass platform is described as galvanized ironwork.
.View attachment 45170
View attachment 45171
While all three vessels were built from essentially the same plans, the effect of the earth''s magnetic field on the so-arranged mass of ferrous metal relative to the position of the Standard Compass would not be known until the first vessel went into service. Titanic went into service less than a year after Olympic consequently, data on induced Standard Compass errors and the positions of compensating magnets on the binnacle was still being collected. You may be surprised to know that the run these ship's were on also had to be considered/
The siting of a standard compass binnacle mid-ship on Titanic was an indication of the shortage of understanding as to how induced magnetism by the earth's field effected the compass combined with the normal practice on standard vessels where the navigation and control center was traditionally amidship or nearly so. In fact. it was found that judicious arrangement of the compensating magnets in the binnacle would allow the standard binnacle to be sited anywhere on the deck. The next big problem was the changing of generated electricity-carrying cables near the compass from DC to AC.
In 1913, the Sperry Gyro Company began producing gyro repeaters for ships in the UK. The RN already had them.
The year following the Titanic disaster was a game-changing one with regards to ship's steering and navigation compasses.