Hi, Ian. One question about one of your components. What is a navigational rangefinder? Where it was usually placed in a ship? That device can also be used for targeting? (I was searching in the www but I only found data of the traditional optical rangefinders). Thanks and cheers!
Posts:5106 Joined: July 26th, 2010, 9:38 pm
The literature describes the small rangefinder above the pilot house of the North Carolina class battleships as the "Mark 35 navigational rangefinder". This same piece of equipment is visible on quite a few other ships of the same time frame. This rangefinder is (I believe) different from the Mark 35 gun director (the single-purpose GFCS fitted to the Porter and Somers class DDs and the Erie class PGs).
Several other sources have mentioned the use of short-base tactical rangefinders for navigation assistance in the days before radar. I'm sure they could also be used to generate range data for targeting, but I don't think they were integrated into the computers aboard the ships (e.g. they could not be used to generate a fire control solution automatically, like the integrated optical rangefinders in the enclosed gun directors).
They probably had the same use as the PIL 'Position-in-Line' rangefinders carried on some larger RN ships during the interwar period. I assume they were used for formation keeping, distances etc. and navigational bearings.
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My historical two cents. Bradley Fiske (USN officer and a holder of numerous patents for navigation aids), is credited in American records as the man who invented and introduced a device into American service that was later called a telemeter. This was a calibrated telescope that measured distances between ships by using a height-finder method based on known mast heights of certain ship classes. Coupled with horizon range tables that were published in a navigator's atlas prepared by the US Naval Observatory, the telemeter could convert angle measurements directly into distances to a target by built in trig computation in the telescope mount itself. It was not precise enough for gunfire as it could only provide a scalar solution with no correction for cross motion, but it was the first instance in the American navy of a ranging instrument better than iron sights and the weather eye. This was in 1888. As far as I know, other navies had inventors who either duplicated or originated their own versions of the Fiske telemeter at about the same time. It is not something historically unique to Fiske. The British and the Germans, I know, were using similar devices for station keeping in formation by 1895 aboard their capital ships. I suggest that modern optical fire control systems, thus, can trace their origins back to such early American, British, and German systems.
I see no reason why a gun director or an optical system similar to a gun director setup, could or would not be part of a US warship's standard nav-aids systems in the 1920s.
Curiously; one of the early USN considerations for the Huhlsmeyer system was as a radio-ranging nav-aid system for station keeping. From there to radar is not that big a leap.