British v German rangefinders

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José M. Rico
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Re: British v German rangefinders

Postby José M. Rico » Sun Jun 26, 2011 10:28 pm

Byron Angel wrote:..... I appreciate your comment and reciprocate the sentiment. These sorts of topics deserve to be discussed in a collegial and decorous manner. This forum need not be an intellectual gladiatorial pit, which seems to occur from time to time.

I wish more people here kept that in mind. Thanks for posting Byron! :ok:

lwd
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Re: British v German rangefinders

Postby lwd » Mon Jun 27, 2011 1:50 pm

Does anyone know how the US FC systems at the time of Jutland compared to the British or German systems? I have read that the US "standards" were considered very deficient by RN standards at the time but this was at least in large part a training problem from what I've read although equipment may have played a part as well.

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Re: British v German rangefinders

Postby Byron Angel » Tue Jun 28, 2011 2:27 am

lwd wrote:Does anyone know how the US FC systems at the time of Jutland compared to the British or German systems? I have read that the US "standards" were considered very deficient by RN standards at the time but this was at least in large part a training problem from what I've read although equipment may have played a part as well.


..... A good book on this subject is "U.S. Battleship Operations in World War 1" by Jerry W Jones. According to the author, when 6th Battle Squadron first arrived at Scapa Flow -
[ 1 ] The US battleships lacked follow-the-pointer (FTP) gear for their main battery turrets. FTP for turret train was only installed during 1917 and FTP for gun elevation not until late 1918.
[ 2 ] US range-finders, although of better performance due to their relatively greater baselength, were sighted too low in the ships and were frequently washed out in the heavy weather often encountered in the North Sea.
[ 3 ] The need to transfer so many experienced officers and trained specialists in order to assist in the rapid expansion of the wartime navy and the influx of new unseasoned recruits had markedly influenced the performance of the existing commissioned ships.
[ 4 ] Main battery salvo patterns were excessively large by Grand Fleet standards - on an order of 2x to 3x larger.
[ 5 ] The US ships were still in the throes of having new design directors fitted - a process which proceeded throughout 1917 and into 1918.
[ 6 ] On a positive note, the Sperry/Ford fire control systems fitted to US battleships gave a generally good account of themselves.

It is a well done book and worth the modest space it wil take up on the bookshelf.

B

lwd
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Re: British v German rangefinders

Postby lwd » Tue Jun 28, 2011 2:09 pm

Thanks for the info and the source.

delcyros
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Re: British v German rangefinders

Postby delcyros » Wed Jun 29, 2011 8:06 pm

Let me also express thanks for providing these informations.

Thorsten Wahl
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Re: British v German rangefinders

Postby Thorsten Wahl » Thu Jun 30, 2011 7:21 pm

From a textbook of optical measurements procedures

"A comparison of stereoscopic rangefinder with other optical rangefinders shows that all procedures are based on the same geometric basis.
Thus they were of same accuracy in general.

Stereoscopic measurement has the advantage, that the accuracy of measurement is not affected by blurred boundaries, such as explosive clouds.
Detached targets wich wich differ from a more distant background can be easisest measured with this procedure.

Goals wich are in rapid motion, or when the measurer is on a rolling ship, then the stereoscopic image measurement is also superior.
Additionally this procedure is also able to deliver a permanent stream of range difference,"

This data should be useful input for the fire control.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: British v German rangefinders

Postby dunmunro » Thu Jun 30, 2011 11:11 pm

Thorsten Wahl wrote:From a textbook of optical measurements procedures

"A comparison of stereoscopic rangefinder with other optical rangefinders shows that all procedures are based on the same geometric basis.
Thus they were of same accuracy in general.

Stereoscopic measurement has the advantage, that the accuracy of measurement is not affected by blurred boundaries, such as explosive clouds.
Detached targets wich wich differ from a more distant background can be easisest measured with this procedure.

Goals wich are in rapid motion, or when the measurer is on a rolling ship, then the stereoscopic image measurement is also superior.
Additionally this procedure is also able to deliver a permanent stream of range difference,"

This data should be useful input for the fire control.


NDRC testing showed that stereo RF accuracy does not scale with increasing magnification and baselength, even under ideal, laboratory conditions:
http://www.sfu.ca/~dmunro/images/RF_extract.pdf
Ft Cumberland trials, showed that while only stereo could range on smoke, there was no difference when ranging through smoke.

The NDRC only contains two detailed trials where B&S CI RFs were pitted against stereo RFs but in both cases a B&S CI unit was the winner. The first trial has already been quoted and the 2nd trial is presented on page 4 and 5 of RF_extract.pdf. In the event the US Army opted for a stereo RF in their M47/48 tanks but were later forced to remove all the stereo RFs and retrofit them with CI units, simply because the stereo units were just not suited for combat, and their operators could not get consistent results. Again, I have to emphasize that the NDRC report shows that the US Army/USN expended very large sums on stereo developement, operator selection and training, but at the end of the day, competitive trials showed B&S CI to be superior.

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Re: British v German rangefinders

Postby Byron Angel » Fri Jul 01, 2011 5:54 am

dunmunro wrote:NDRC testing showed that stereo RF accuracy does not scale with increasing magnification and baselength, even under ideal, laboratory conditions:
http://www.sfu.ca/~dmunro/images/RF_extract.pdf
Ft Cumberland trials, showed that while only stereo could range on smoke, there was no difference when ranging through smoke.

The NDRC only contains two detailed trials where B&S CI RFs were pitted against stereo RFs but in both cases a B&S CI unit was the winner. The first trial has already been quoted and the 2nd trial is presented on page 4 and 5 of RF_extract.pdf. In the event the US Army opted for a stereo RF in their M47/48 tanks but were later forced to remove all the stereo RFs and retrofit them with CI units, simply because the stereo units were just not suited for combat, and their operators could not get consistent results. Again, I have to emphasize that the NDRC report shows that the US Army/USN expended very large sums on stereo developement, operator selection and training, but at the end of the day, competitive trials showed B&S CI to be superior.



..... Thanks for making the NDRC pages available for perusal - fascinating reading. However, I must admit to being rather mystified by the dramatic conclusions you have drawn from this text.

[ 1 ] The initial discussion of the tests of the M1/M2 stereoscopic height-finder confines itself to an examination of the fact that increases in magnification did not confer increases in accuracy of readings that were in accord with those predicted solely on the basis of basic optical theory. This was well known as early as WW1 when it became evident that better reading accuracy provided by increased magnification was offset to some degree by reduced image brightness resulting from said magnification increase. The consistency of RCS (range correction setting) for both 12x and 24x settings is a minor point - stating that the same correction setting for differences in operator, temperature, weather, distance, etc, on any given day would serve equally well for either magnification setting. The rest of the discussion revolves around UOE (units of error) and quantified the observation that improvements in accuracy versus magnification fell considerably short of theoretical expectations. This phenomenon applies equally to both coincidence and stereoscopic range-finders and, in fact, no comparison of any sort between the two design types was broached by the authors.

[ 2 ] The second discussion of Harvard University test of the influence of base-length by testing long base-length stereoscopic range-finders (18 - 46 ft) at distances over water up to 6,400 yards (akin to using a sniper rifle to hit a milk carton on the other end of one's kitchen table) simply observed that accuracy tended to increase with base-length, although again not to the degree suggested by theory. The influence of base-length is a design fundamental which applies equally to both coincidence and stereoscopic range-finders, and, once again, the authors offered no discussion of relative merits of coincidence versus stereoscopic range-finder design in this section.

[ 3 ] The third discussion of further Harvard University tests evaluating the effect of magnification upon stereoscopic acuity over ranges between 50 yards and 6,400 yards using magnifications ranging from 1x through 40x concluded that all the range-finders tested consistently delivered sub one percent average range errors at all ranges and magnifications tested, a value which the authors found “unexpectedly low. Yet again, no comparison was made between performance of coincidence versus stereoscopic instruments.

[ 3 ] The final excerpt relates to an evaluation of range-finders for use by the Tank Corps – instruments to be fitted into large numbers of AFVs. Bausch & Lomb conducted comparative field tests of the following instruments –

Keuffel & Esser invert coincidence (1M, 12x)
Keuffel & Esser superimposed coincidence (1M, 12x)
Keuffel & Esser stereoscopic reticle (1M, 12x)
Barr & Stroud Mk VI (1M, 14x)
Perkins & Elmer superimposed coincidence (48”, 6x)
Polaroid stereoscopic, illuminated reticle (43”, 1x)

The selected operators were ten “untrained” enlisted Tank Corps personnel. Approximately 15,000 readings from about 600 to 6,000 yards were said to have been taken over a three week period. In the hands of these “untrained” operators, the coincidence range-finders gave the best performance in terms of percent of error. This is not surprising IMO given untrained operators certified as possessing no better than standard visual acuity. Use of the coincidence method is more intuitively obvious to the untrained operator than the stereoscopic type – a fact with which I have personal experience – and the lack of operators with proper stereoscopic acuity would have affected the results delivered by the stereoscopic instruments. On the other hand, however, the Tank Corps was seeking an instrument that would be deployed for use in the tens of thousands, as opposed to the hundreds only as required by the Navy. The interesting upshot of the test was that the UOE (a measure of instrument precision) of the Polaroid stereoscopic instrument was pointedly mentioned as being dramatically superior to all other competing instruments, with even the Barr & Stroud Mk VI (the best of the coincidence range-finders) making a “poor second”.

To make a long story short here – and I recommend that all interested parties peruse the document themselves in order to get a fully balanced appreciation - the Barr & Stroud Mk VI coincidence range-finder was recommended for use by the Armored Force as “the best immediately available instrument” for the wide-scale use intended. However, the performance of the Polaroid instrument and, apparently that of other stereoscopic instruments, was sufficiently impressive to induce the Fire Control section of the NDRC itself to advise with respect to the development of an AFV fire control system - “In the further investigation of an instrument, consideration should be given to a stereoscopic instrument of the illuminated reticle type because such an instrument could be of extreme value for correction of range as well as obtaining initial range for opening fire”, a position further endorsed by a letter from the Chief of Section 7.4 NDRC to the Office of the Chief of Ordnance which mentions the “the scheme contemplates the use of a range finder of stereoscopic type”.

In closing, I do not by any means see here a “smoking gun” validation of the superiority of the coincidence range-finder over the stereoscopic type.


B

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Re: British v German rangefinders

Postby dunmunro » Fri Jul 01, 2011 8:59 am

The B&S was also compared, indirectly to a 1.5m USN stereo RF:

The results of this experiment indicate that the experts were better than the novices on all instruments There is relatively little difference between these two classes of observer on the coincidence instrument. There were relatively great differences between the experts and the novices w ith the stereoscopic instruments. There was little difference in the results for all for the instruments when used by experts. The Mark 58 regular reticle rangefinder
( http://www.hnsa.org/doc/rangefinder/index.htm ) was poorest, for targets of this type, for both novices and experts...

P.5 of the pdf.
.

and in testing by B&L, expert and novice observers were used, and again B&S CI bested the stereo competition, and two other CI RFs. I have followed up on the use of stereo in US tanks, and I'll repeat it again: stereo was found to be unsuited for combat and replaced by CI, so the original NDRC recommendation held up 10 years later. An interesting finding was that the 1x Polaroid stereo RF had very low UOE, and undoubtedly would beat a 1x CI with the same base-length, but the problem with stereo, as I've taken pains to point out, is that it doesn't scale up with increasing magnification and base-length, as CI does, so at roughly equal base-lengths and appropriate magnification, CI wins.

We have the RN Ft Cumberland trials: Little difference but CI recommended for ease of use. NDRC stereo versus 18ft CI, 13.5ft stereo and a 9ft CI, and the 9 ft CI was noticeably better than a 13.5ft stereo, and the finding was no difference between stereo and CI, which of course is actually a powerful endorsement of CI and finally the tank RF trials and B&S CI won again. The most obvious finding was that only experts could get the best out of stereo but even novices could compete with experts when using CI, but again if stereo is no better than CI, then why bother? This is exactly the conclusion reached by Ft Cumberland; stereo just isn't worth the effort because it doesn't produce greater accuracy to make up for it's much greater operational costs.

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Re: British v German rangefinders

Postby Byron Angel » Fri Jul 01, 2011 12:51 pm

dunmunro wrote:The B&S was also compared, indirectly to a 1.5m USN stereo RF:

The results of this experiment indicate that the experts were better than the novices on all instruments There is relatively little difference between these two classes of observer on the coincidence instrument. There were relatively great differences between the experts and the novices w ith the stereoscopic instruments. There was little difference in the results for all for the instruments when used by experts. The Mark 58 regular reticle rangefinder
( http://www.hnsa.org/doc/rangefinder/index.htm ) was poorest, for targets of this type, for both novices and experts...

P.5 of the pdf.
.

and in testing by B&L, expert and novice observers were used, and again B&S CI bested the stereo competition, and two other CI RFs. I have followed up on the use of stereo in US tanks, and I'll repeat it again: stereo was found to be unsuited for combat and replaced by CI, so the original NDRC recommendation held up 10 years later. An interesting finding was that the 1x Polaroid stereo RF had very low UOE, and undoubtedly would beat a 1x CI with the same base-length, but the problem with stereo, as I've taken pains to point out, is that it doesn't scale up with increasing magnification and base-length, as CI does, so at roughly equal base-lengths and appropriate magnification, CI wins.

We have the RN Ft Cumberland trials: Little difference but CI recommended for ease of use. NDRC stereo versus 18ft CI, 13.5ft stereo and a 9ft CI, and the 9 ft CI was noticeably better than a 13.5ft stereo, and the finding was no difference between stereo and CI, which of course is actually a powerful endorsement of CI and finally the tank RF trials and B&S CI won again. The most obvious finding was that only experts could get the best out of stereo but even novices could compete with experts when using CI, but again if stereo is no better than CI, then why bother? This is exactly the conclusion reached by Ft Cumberland; stereo just isn't worth the effort because it doesn't produce greater accuracy to make up for it's much greater operational costs.



..... No one is arguing the ability of a coincidence range-finder to obtain accurate ranges. No one is arguing that a stereoscopic range-finder is innately mechanically more accurate. No one is arguing that coincidence range-finders are not easier to use for the typical operator and therefore more suitable in cases of large-scale deployments. It is however equally evident that the particular nature of stereoscopic range-finders enables them to measure ranges under visibility and imagery conditions where a coincidence range-finder is unable to do so. The USN thought so; they fitted their most modern BBs with stereo. The RN came to the same conclusion, if their 1943 Progress in Naval Gunnery report on stereo is to be believed. The Kriegsmarine and just about every other major navy in the world fitted their capital ships with stereo. Why is all this simply dismissed by you?

Sorry to be sharp here, but your repeated recitations of the same specific portions of these two documents do not serve to advance the discussion. You seem to focus on the information that supports your position and dismiss information that is contrary to it or calls it into question. For example, unless you possess a great deal more detail on the Bausch & Lomb tests of the Polaroid stereoscopic range-finder that is not available to us, your characterization of the commentary about the Polaroid's UOE performance is a mischaracterization of the text. The paragraph CLEARLY states that the Polaroid stereoscopic range-finder had a dramatically better UOE performance, outpacing even the B&S Mk VI that had otherwise won the overall test. I see nothing whatever in the text that qualified that statement on grounds of magnification. If there is more info bearing on this, please do share.

And what do you make of the NDRC's final recommendations to pursue development of stereoscopic range-finders for the tank force? The NDRC apparently came to that conclusion based upon exactly the same tests you cite as proof that coincidence range-finders are the obvious choice. Please explain.

- - -

For whatever it's worth, a very close friend of mine was as a gunner on the M60 in the late 1960's. He trained on a stereoscopic range-finder and his vehicle was fitted with one. I'm not sure how that squares with your information, or how meaningful it is, but take it for what it's worth.

B

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Re: British v German rangefinders

Postby dunmunro » Fri Jul 01, 2011 8:35 pm

Byron Angel wrote:


..... No one is arguing the ability of a coincidence range-finder to obtain accurate ranges. No one is arguing that a stereoscopic range-finder is innately mechanically more accurate. No one is arguing that coincidence range-finders are not easier to use for the typical operator and therefore more suitable in cases of large-scale deployments. It is however equally evident that the particular nature of stereoscopic range-finders enables them to measure ranges under visibility and imagery conditions where a coincidence range-finder is unable to do so. The USN thought so; they fitted their most modern BBs with stereo. The RN came to the same conclusion, if their 1943 Progress in Naval Gunnery report on stereo is to be believed. The Kriegsmarine and just about every other major navy in the world fitted their capital ships with stereo. Why is all this simply dismissed by you?

The paragraph CLEARLY states that the Polaroid stereoscopic range-finder had a dramatically better UOE performance, outpacing even the B&S Mk VI that had otherwise won the overall test. I see nothing whatever in the text that qualified that statement on grounds of magnification. If there is more info bearing on this, please do share.

And what do you make of the NDRC's final recommendations to pursue development of stereoscopic range-finders for the tank force? The NDRC apparently came to that conclusion based upon exactly the same tests you cite as proof that coincidence range-finders are the obvious choice. Please explain.

- - -

For whatever it's worth, a very close friend of mine was as a gunner on the M60 in the late 1960's. He trained on a stereoscopic range-finder and his vehicle was fitted with one. I'm not sure how that squares with your information, or how meaningful it is, but take it for what it's worth.

B


You are making a very effective case for CI...just as the RN did at Ft Cumberland.
Ft Cumberland trials found that the main reasons for the superior performance of the Zeiss stereo units under adverse visibility was their greater light gathering ability through larger apertures and better mounting design. When a CI unit was designed with similar features it had similar adverse lighting capability, and the final recommendation by Ft Cumberland was for a B&S FX CI unit, optimized for low light capability. Again, during WW2 the RN got hoodwinked into believing that stereo was superior since the USN was apparently using it to blast the IJNAF out of the sky...however, as it turned out the USN's claims were inflated by nearly an order of magnitude, and the USN's AA performance was no better than the RNs, and probably worse. Other navies did use stereo, although the IJN and RM used stereo and CI together, and the USN included CI, usually as a turret RF, in at least one turret, which as we've seen was the only RF able to obtain a range against an enemy BB.


The NDRC volume on rangefinders looks mainly at stereo because the US armed forces mainly used it. There is only the two example of CI versus stereo, but in both cases a B&S CI unit proved superior. As I've said before B&S had patents on superior forms of CI, and many countries did not want to use a foreign made or designed RF (witness the NDRC B&S CI recommendation which were rejected by the US Army...)

A UOE (A UOE is usually the theoretical performance based upon 12sec of arc error at the stated range, magnification and baselength) is based upon the base length and magnification of a RF. What the NDRC was saying was that a 1 power 1m Polaroid had lower UOE than a 14 power 1M CI unit, of course they assume that the reader realizes that one UOE in a 14 power 1m instrument is 14 times smaller, than one UOE in a 1 power, 1m instrument. The researchers made the logical conclusion that if they could make a stereo RF with increased magnification, without increasing the UOE, that it would be the best possible RF...unfortunately they didn't realize that stereo just doesn't scale up according to the theory of geometric precision, so we see a 24x stereo versus 12x with the same baselength only gains ~1.2x in precision rather than 2x, even under laboratory conditions and this is not problem with the optics or visibility, but is an inherent limitation of stereo.

The final improvement inaugurated in the M60 involved replacement of the M48 tank's stereoscopic range finder, adopting in its place a coincidence range finder which was easier to use and more effective in actual service. ..
United States. Army Materiel Development and Readiness Command. Development and Engineering Directorate
M60 Main Battle Tank. In early 1956 the US Army decided to improve the the M48 Patton tank. Improvements included...a coincidence range finder...Historical dictionary of the U.S. Army
Typical of its evolutionary nature, the original M60 resulted from mating a105mm gun and an AVDS-2 diesel engine with an M48. Combat units inEurope first received the M60 in Decem-ber 1960, and a total of 2,205 M60swere built. Subsequent modifications made the M60-series more distinctive.These changes included a longer turretmore suited to the 105mm gun, bettersuspension, a redesigned commander’s cupola, a T-bar instead of a steeringwheel, better armor protection, an electrical computer, and a coincidence range-finder. The last device proved much simpler to operate than the stereoscopic rangefinder. The viewer observed the target as a split image. Aligning the image determined the range. These modifications resulted in the M60A1 that re-placed the M60 on the production line,starting in October 1962. The production run stopped in 1980 after 7,948 M60A1s had been built. American Tank Development During the Cold War, Armor, Sept 1997.

However, the RF used prior to the upgrade was stereo, and AFAIK, all stereo units were eventually replaced by CI.

Edit: I am not trying to be difficult or argumentative, but I am defending the conclusions of the Ft Cumberland trials, because I believe that they have stood the test of time and are validated by the NDRC's studies 20 years later. I do not believe that the Ft Cumberland trials were rigged or biased, but the conclusions reached at Ft Cumberland were done so on an objective and scientific basis.

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Re: British v German rangefinders

Postby Byron Angel » Sat Jul 02, 2011 4:21 am

As I believe I have mentioned before, your defense of your position is certainly tenacious, but IMHO ultimately unconvincing. I plan on making this my last post on the issue, but in so doing will also ask some questions to which I hope you will respond. 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.

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.

> 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?

> 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?

> 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?

> 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.)

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 .....

B

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Re: British v German rangefinders

Postby dunmunro » Sat Jul 02, 2011 8:13 am

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, see
http://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:

STEREOSCOPIC RANGEFINDERS

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 .....

B


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.

Byron Angel
Senior Member
Posts: 730
Joined: Sun Mar 06, 2011 1:06 am

Re: British v German rangefinders

Postby Byron Angel » Sat Jul 02, 2011 1:01 pm

Sorry, dunmunro, but for me your reply just smacks too much of cherry picked data for me to accept your argument.

We will just have to go our separate ways on this, I'm afraid.


B

Thorsten Wahl
Senior Member
Posts: 643
Joined: Mon Apr 27, 2009 4:17 pm

Re: British v German rangefinders

Postby Thorsten Wahl » Sat Jul 02, 2011 4:15 pm

I pretty sure german optics of the WW1 timeline were somewhat better than their british counterparts.
I remember reading about a british offer via a neutral country regarding sniper optics for rubber.

Incidentally my textbook is from the end of the fifties. Hence it should include also summarised knowledge from the worldwars.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!


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