Byron Angel wrote:As I believe I have mentioned before, your defense of your position is certainly tenacious,
The RN did exhaustive and extensive testing of stereo versus CI, and they chose CI. I am arguing that the RN trials and their clearly stated conclusions were/are valid. You are arguing that the trials and their conclusions were, in effect, fraudulent. I don't believe that.
Several of these questions have been raised before, but have so far received no response.
A coincidence type range-finder will indeed benefit from use of better quality optical glass, suitable lens coatings, increased aperture size, and a judicious selection of magnification level. But none of that will in any way whatsoever compensate for the need of a coincidence type naval range-finder for a distinct vertical element upon which to make a range cut. The ability of a stereoscopic type range finder to take ranges upon amorphous and indistinct target images which do not offer a strong vertical element is what sets it apart. This was mentioned time and time again in the Fort Cumberland trials, but you for some reason choose to ignore this fact. I'm really not sure why.
There are a number of CI designs such as superimposed coincidence (commonly used on rangefinder cameras in the 1950s and 1960s) and the strip field CI (used in RN AA RFs)that do not need a distinct vertical element upon which to make a cut, but the other factor is that stereo has great difficulty in ranging accurately on indistinct objects and/or in poor lighting and poor accuracy is worse than no ranges at all - which is another finding of Ft Cumberland (see the end of this post). Note the lack of ranges from Washington's multiple stereo RFs. A CI range, if it can be obtained, can be trusted.
Another unique feature of the stereoscopic type range-finder so far not discussed was its ability in naval surface gunnery to accurately spot and measure fall of shot in relation to the target (scartometry) - a function that the coincidence type range-finder was, by its nature, unable to perform.
Unfortunately, this capability was seldom used since it was range dependent and at long ranges, where it was really useful, it didn't work. It also overloaded the RF operators, who really needed to concentrate on range taking. See http://www.admirals.org.uk/records/adm/ ... 86-339.pdf
, p.150. The RN continued to investigate the use of stereo for AA, and they looked at using it for AA scartometry, but never did.
> You cite the referenced NDRC report as convincing proof of the superiority of the coincidence range-finder type over the stereoscopic type on one hand, but deprecate the conclusions of the very same report where it praises the stereoscopic type. On what ground are we to believe, for example, that the very same scientists whose observations you cite in support of your argument can have suddenly missed the mark completely when they praised the UOE performance of the Polaroid stereoscopic range-finder?
The US Army used stereo and then had to reverse their position (20 years later)...doesn't this validate the conclusion that the B&S was/is the best available RF for that task? How, in any way can this be used as an argument for stereo?! I presented evidence showing that stereo doesn't scale well, and all the stereo RFs of aprox equal or greater magnification to the B&S Mk VI proved inferior in the NDRC testing, and as the US Army later admitted in rather convincing fashion, in actual use.
> Can you provide some corroboration of your assertion that the sterescopic range-finder suffers uniquely more severely in terms of "scaleability" than the coincidence type?
I presented several pages of data from the NDRC showing poor scalability for stereo. You chose to ignore that data or dismiss it and the fact that short base, high magnification CI units defeated equivalent longer base stereo units at Ft Cumberland, NDRC trials, and later US Army trials, IMHO, validates the NDRC findings.
> What is your response to the closing remarks of the NDRC report which urged that special attention be paid to the development of stereoscopic type range-finders for use in an integrated AFV fire control system? Were the NDRC scientists wrong again?
The report recommended further development of stereo, presumably based upon the assumption that its inherent problems could be overcome, but the US Army chose to go with stereo straight away, and ended up with a less than suitable FC system and, apparently, even 20 years later stereo was still not suitable because they chose to retrofit stereo equipped tanks with CI rather than an improved stereo.
> How do you square the fact that the USN favored stereo as their principal range-finder for surface gunnery, as did the German navy of WW2, as did the French navy, with even the RN changing its mind to endorse stereo for naval gunnery application by 1943? Were the researchers and scientists of all these navies in error?
(note here - the heavy surface gun batteries of major surface units of the Japanese and Italian navies of WW2 were typically fitted duplex and triplex range-finders of mixed stereo/coincidence types; Japanese and Italian range-finders for AAA control appear to have been stereoscopic.)
The largest navy in the world, the RN with the most experience in actual combat, decided that CI was superior, and one main reason, which I have emphasized repeatedly is that if the two system are equal then CI always wins because of its lower operational costs. The IJN used CI almost exclusively for LA RFs, with Yamato being one of the few units with LA stereo RFs, although according to Anatomy of the Ship, Yamato
, she only had a single LA stereo RF (one of 3 in her 15m triplex RF). We all know how ineffective IJN AA was, so their use of stereo HA RFs was no advertisement for stereo superiority. However, the two best WW2 navies for night fighting capability were the RN and IJN, and they both used CI RFs, almost exclusively for LA ranging ( see Japanese Cruisers of the Pacific War
which states that all IJN cruisers used 100% CI for LA ranging). The RN reported good success in ranging on aircraft, at night with CI RFs, seehttp://www.admirals.org.uk/records/adm/ ... 86-339.pdf
, p 159 - 161.
so under the most challenging conditions CI continued to be useful and proved itself in combat. Stereo, OTOH, did not live up to its billing, but this didn't stop the USN from making outrageously exaggerated claims for stereo based AA systems and this influencing the RN into making a temporary lapse of judgement:PNG19 42-43:
85. As is well known almost all foreign navies have adopted the stereoscopic principle for all or some of their rangefinders, whereas we have always usedthe coincidence type only.
During the past year this policy has again been reviewed, largely because of the extreme difficulty of obtaining a “cut” on the modern aircraft which, from many aspects, presents only a horizontal line on which to range. This time was, moreover, an excellent one at which to give further consideration to the subject since we had access to a large amount of data collected by the U.S. authorities, as well as the benefit of the experience of some of our other allies.
Unfortunately, the US data does not make the case for stereo being more efficient than CI, even under adverse conditions and their AA overclaiming during combat provided a completely false picture of stereo AA ranging effectiveness.
Not to unduly belabor this, but it bears repeating that I am not trying to make a case that one type of range-finder is categorically superior to another in all respects. To even approach the issue from such a mindset is in my opinion foolish. Both types had their uses, their advantages, and their unique defects. The only reason I am glazing everyone's eyes over is to press forward the point that resolving such technical issues are great deal more complicated than pulling isolated bits and pieces of data from selected artificial tests and holding them up as definitive proof of anything. Here is an excellent example of the falsity of doing so. Let us examine the Grand Fleet Gunnery & Torpedo Memoranda of WW1 and see what its has to say about the performance of its 9-ft Barr & Stroud coincidence range-finders -
Falkland Islands - (fought in excellent basic visibility at ranges of 10-16,000 yards)
"Rangefinders found of little use due to long range, spray from enemy short shots, and funnel smoke".
Dogger Bank - (fought in excellent basic visibility at ranges of 15-20,000 yards)
"Little use could be made of the range-finders as few cuts could be obtained, whilst the range was too great for accurate readings to be taken;"
Action between 5th LCS and German 1SG - (fought in poor light conditions at ranges of approx 14-15,000 yards)
"The range was approximately 16,000 yards, but this is poor estimation, as owing to the bad light no ranges were obtained."
Jutland - too voluminous to wade through tonight. Read the Jutland Despatches, The Fighting at Jutland, the ONI Staff Appreciation of Jutland,
Campbell, and the RN Staff Analysis of Jutland (all now miraculously available on the internet)
Second Heligoland, 17 Nov 1917 - (fought under basic visibility of 15,000 yards, at ranges of approx 10-15,000 yards)
"Two ships appear to have got good results, others report few readings were obtained, and one ship reports a total failure.
Ranges were seldom obtained before fire was opened, so that on practically all occasions fire was opened with a guessed range.
Periods of fire were so spasmodic, and visibility so poor (Byron note - Germans made great use of obscuring smoke) that rangefinder
observations generally were of little value for rate-keeping."
I do not seek to draw any momentous conclusions from the above excerpt other than to point out that tests are tests, actual combat is actual combat, and conclusions drawn from the former do not necessarily equate to the latter.
For whatever it's worth to anyone .....
No, I am not making a blanket case for CI superiority either, but when both types of RF have equally well engineered mountings and optics, then it is likely that the CI units will be superior in overall use. The fact that an early model 9ft CI RF had problems with ranging at long range and/or in poor visibility is hardly surprising. The 9ft UB7, OTOH was proven to range with high accuracy out to 12000 yds against aircraft and ships, and outperformed a 13.5ft stereo RF. From PNG 1922:The series of trials under report show that, in addition, with the modified structure (i.e., less vibration) the stereo has lost its superiority at high speeds, and further that on difficult objects, provided the coincidence rangefinder is able to get any ranges at all, the stereo is worse as regards accuracy and consistency, and only scores through obtaining more ranges per minute. On several occasions in low visibility with ill-defined object, the stereo was able to range when the coincidence could not, but on comparing the ranges obtained with the true ranges they were found to be very much in error, and in practice would have been useless and misleading.
The IJN, as I have stated used CI exclusively on their cruisers, and the IJN were deadly efficient at night... so in actual combat in WW2 seems to validate the CI's performance in low visibility situations.