I’m not sure. Who used them besides the Italians? Russians perhaps?Tiornu wrote:How does a scartometer differ from a rangefinder?
Brad
I’m not sure. Who used them besides the Italians? Russians perhaps?Tiornu wrote:How does a scartometer differ from a rangefinder?
Stereo rangefinders were checked and calibrated at regular intervals. Under ideal conditions the amount of error is, as Brad has said, a combination of human error and a degree of error unavoidable with the instrument itself, as no optical instrument is completely flawless. The amount of error on the part of the operator can increase over time, which is why a rangetaker's eyesight was checked frequently and he was required to practice and be scored on a regular basis. In short term, changes can occur as well. The amount of error increases with stress, lack of sleep, and fatigue. In the latter case, eye fatigue can play a part in very long actions and an operator might experience gradual increase in error on his part the longer he is at the rangefinder.I find myself astonished that optical rangefinding could be that good. Presumeably there was calibration carried out against surveyed targets to confirm this? Surely this performance dropped off very rapidly under service conditions?
I apologize for the belated reply. Those rangefinder numbers represent theoretical calculations and representative of a good, well trained operator who has plenty of experience. The figures I gave for the 26.5’ Mk 48 in the Mk 38 directors is likely to be quite accurate since it’s based on actual fleet experience. The Yamato figures are more theoretical because there is very little information on Japanese rangefinder design. Several big questions such as are they stabilized, do they have light enhancing coatings, glare filters etc come to mind.wadinga wrote: What does seem clear is that by 1945 radar has become the primary source of information for both functions. I am still trying to home in on the relative performance of the two techniques, as I think Brad's examples suggest at least the Mk 3 was no better at 20,000yds than optical rangefinding with an 8m Iowa rangefinder but that a Yamato 15m was twice as good, +/- 155yds v +/- 85 yds. Is this real?
However if the spotter switches between measuring the range to the target, and positioning his wandermark on his estimate of where he thinks the MPI of the current salvo is, the rangereader will have to know which he is doing, and when sending to the transmitting room- differentiate. Also there does not seem to be a mechanism for sending right/left error of the MPI from this system.Two men operate the rangefinder-the spotter, who sights on the target and positions the wander marks, and the rangereader, who reads the range.
I am not too sure about the US approach to spotting, but in the German practice, the rangefinder was kept with the Wandermark on target at all times (and thus continued to give range readings) and spotting fall of shot was done with the lateral and vertical lines of diamond markers in the reticle pattern. Each diamond represented an increment of vertical or lateral distance, usually something like 200m increments in range and 50m increments in lateral distance. So if the spotter sees the the farthest and closest splashes as having a spread of say 200m and the right and left splashes as having a spread of 100m, he can easily give a rough estimate of the MPI without taking his Wandermark off the target. The spotter can thus give a verbal estimate to the controlling Artillerieoffizier of the necessary correction for up or down and right or left without interrupting the flow of range data.However if the spotter switches between measuring the range to the target, and positioning his wandermark on his estimate of where he thinks the MPI of the current salvo is, the rangereader will have to know which he is doing, and when sending to the transmitting room- differentiate. Also there does not seem to be a mechanism for sending right/left error of the MPI from this system.
You must find Warship International 1986, No4 and look on p334. According to gunner data,Warship International ref from maybe 15 years ago in which a former Iowa gunnery man said their Topspot 1 rangefinder was +/- 1000 yds at 30,000 yds.
I agree. In the russian practice the command rangefinder station (american and british analogs is Spot or DCT, if I saving correction) usually had 2-3 single rangefinders, one of them give range on target, another on splashes and third could execute either of two tasks. With the exception of italian rangefinder which had built-in scartometer and could measure deviation of salvo directly. However the single imported model with scartometer which used by navy before and during war was an OG3 - Galileo 3m stereo rangefinder, installed on some destroyer leaders. Also I have read that as a last resort possible to use the single stereoscopic rangefinder. However unclearly how effective such method in practice. In case of maximum magnitude the field of view quite limited (~ 1 degree for 8m RF operator!) and some salvos simply will be drop out of sight.It seems IMHO the range of jobs described for the spotter would be very difficult to do from the eyepiece of the rangefinder, so surely somebody else is doing this.
Assessing longs and shorts, as well as right and left limits of the fall of shot pattern is difficult at longer ranges. As you and Mr Skelly surmise, it is easier when the entitre splash from base to top can be seen. When the splash bases are hidden by the horizon one has less time to make an estimate before the water column collapses. as range increases more and more of the splashes will be hidden and less and less time is available for the the spotter to make his estimate. I think this is what Herr Skelly is implying when he says it becomes a matter of sensing longs and shorts.BTW, such question. Mr.Skelly (who was in Iowas's fire control team) asserted that "at 26.000 yards and beyond establishing fall of shot MPI error in relation to target is difficult to impossible as to magnitude - it becomes a matter of sensing longs and shorts..." I.e up to 26.000 yds a possible direct method using? Is it connected with the splash base beyond the horizon or there is something else in mind?
In Germany too, the main spot estimate was done by the control officer at the director. His optics were a similar to a modern stereo panoramic sight. The fire control station in the foretop and forward control station also had a binocular panoramic sight used as a spotting glass, so the whole spotting proceedure was a matter of teamwork with estimates from three sources being used to evaluate fall of shot.In the russian practice the command rangefinder station (american and british analogs is Spot or DCT, if I saving correction) usually had 2-3 single rangefinders, one of them give range on target, another on splashes and third could execute either of two tasks. With the exception of italian rangefinder which had built-in scartometer and could measure deviation of salvo directly.
Oh, don't mention it. There are only few efficient articles about fire control and they almost get by heart.:-)Thankyou for doing what I should have done myself and locating the source. I have that letter and article in front of me and am working through them. Like you I do not understand what "units of error" are, but to get to .1 yds at 30,000 must surely be a mathematically derived theoretical. The article says radar and optical could match at 44,000 yds to within 100yds, Mr Skelly's letter says 500-1000, (which is what I remembered (kind of ).
I do not know really. I only have some of the common knowledge, not in so more details as yours or Tommy. As one book says this is complementary optical system, built-in to the rangefinder. The OG-3 mentioned above can to measure the deviation for salvos landed within interval +/- 15 cabels with it help, i.e. this is about +/- 3000 yds relative to target.Unlike you I have no idea what a Scartometer is, and Google comes up with nothing. Can you enlighten me?
I hope that Mr.Fischer will clarify this.Skelly says 26,000 yds is the limit for direct spotting, the USN manual suggests 18,000, Height of observer is obviously important but how often does one get a clear, sharp horizon?
Seems you are right. Another question that the splash itself has unstable form while for correct focusing is required clearly expressed stable border. Unclearly how rangefinder operator concentrated own attention when necessary to make a "cut". The point of aim the splash base or possible higher, i.e. if the splash slightly hidden behind the horizon?When the splash bases are hidden by the horizon one has less time to make an estimate before the water column collapses. as range increases more and more of the splashes will be hidden and less and less time is available for the the spotter to make his estimate.
Something like slightly improved ww1 technique if take into no account the control position height and stabilization. I read memoirs by Herr Haaze, IIRC, he used for spotting the stereoscopic telescope in the upper part of the conning tower which simultaneously operate as director sight. Germans never used rangefinder exclusively for salvo ranging?In Germany too, the main spot estimate was done by the control officer at the director. His optics were a similar to a modern stereo panoramic sight. The fire control station in the foretop and forward control station also had a binocular panoramic sight used as a spotting glass, so the whole spotting proceedure was a matter of teamwork with estimates from three sources being used to evaluate fall of shot.