Will the accuarcy of an stereoscopic rangefinder be affected by misidentifing the tar

[vadupleix]

Will the accuarcy of an stereoscopic rangefinder be affected by misidentifing the target?
I just read the following sentence in Peter Lienau's article 'German Optical Rangefinders' :

Unknown to the British, stereoscopic systems also have an advantage in that they cannot be "spoofed" by changing the profiles of the target, which meant that the British wasted a great deal of effort during WWI by adding various extra details to their ships with that intent.

but i can't figure out how can the size of a target misleading the range?

thanks a lot~

[Dreadnought]

Perhaps what they are implying is that the Brits added various visual obstructions that would "catch" the eye of the German optical operators and focus their attention or confuse their vision. Since you couldnt fool the instrument itself (outside of fouling from exaust gases, fogging etc) fooling the operator of that instrument was probably worth the effort. Remember you had to be able to focus your eyes and attention at all times even during battle, rough seas etc and concentrate to get a proper range bearing. Somewhere along the same lines of painting false bow waves on ships to confuse size and speed, and the "dazzle" cammo paint jobs some ships recieved that plain out annoyed your vision. If you could disrupt the optical operators vision and concentration then perhaps he may make a mistake in his ranging to target and miss all together.

[Gun Grape]

Will the accuarcy of an stereoscopic rangefinder be affected by misidentifing the target?
I just read the following sentence in Peter Lienau's article 'German Optical Rangefinders' :

Unknown to the British, stereoscopic systems also have an advantage in that they cannot be "spoofed" by changing the profiles of the target, which meant that the British wasted a great deal of effort during WWI by adding various extra details to their ships with that intent.

but i can't figure out how can the size of a target misleading the range?

thanks a lot~

As you reference stated. It won't. Stereoscopic sights work off the Parallax principle.

The British countermeasures would have worked if they had used the Stadia (mil relation) method of determining distance. Because it changes the known height of the object measured. Messes the WoRm formula up because the measured angle is off. GIGO.

[vadupleix]

Cuz there goes the saying that Hood was misleaded for they wrongly identified the Prinz Eug as Bismark, so they got the wrong range (As they got there salvo far behind their target, I guess that may also be mistake in bearing), that is to say the size of a target(not painting of it) may affect the result of target range&bearing, by what way?

[Gun Grape]

Mis identifying the ship wouldn't give them the wrong range.

What, most likely, caused the range error was the fact that they could not use their 30 foot optical range finders due to weather and instead had to rely on the 15 foot one in the spotting top.

The mis ID of the ships meant that PoW was firing at Bismark while Hood fired at Prinz Eugen, instead of them concentrating their fire on one ship.

One thing that you must remember is that during this battle all the ships are moving and changing speed and direction.

Luck plays more of a part in naval gunfire battles than anything else.

An example is the USS Mass vs the Jean Bart. Jean Bart tied up at dock,

Mass fired for an hour and a half, expended over 200 rounds at the Jean Bart
and hit her 5 times.

[DonBelt]

Ahh, but Big Mame hit a number of other ships around the Jean Bart as well as some shore installations in the process- so it wasn't a total loss. I'd place it under "fire for effect".

[Gun Grape]

Not a total loss. But she was aiming at the JB at the time.;)


Not the most accurate weapon in the world.

The article is trying to blame the inherent inaccuracies of a gun, and its performance in battle on optics.

I would love to see what the range spread on Hoods guns were at that distance.

[USSWisconsin]

JB hit 7 times by BB59

An example is the USS Mass vs the Jean Bart. Jean Bart tied up at dock,

Mass fired for an hour and a half, expended over 200 rounds at the Jean Bart
and hit her 5 times.

Jordan and Dumas, French Battleships 1922-1956, describe seven 16" hits on JB

#1 0725 hit the deck at 33 deg, ripped through refrigeration plant, pentrated both AD's entered 6" magazine (empty) exploded against armored bulkhead , base of shell ripped into the turbo generator room.
#2 0735 went through forefoot didn' explode, caused flooding
#3 0737 went through funnel at 31 deg, ripped through upper decks, exited port side clipping the top edge of the AD, didn't explode
#4 0737 hit wall of dock, went through shell plating bounced off main belt at frame 88, buried in harbor bottom, did not explode, shrapnel from concrete quay took out AA battery crews, caused flooding
#5 0806 hit turret #1, destroyed 90mm subcaliber gun, jammed turret (JB's only operational turret).
#6 0806 hit barbette #2 broke up, and the base of the shell penetrated the upper decks and ricocheted off the main armored deck, and secondary barbettes on a long destructive trajectory through the middle of the ship.
#7 0810 struck quarterdeck near starboard catapult, penetrated 100mm inclined AD, exploded in a fuel tank under steering gear, nose of shell exited bottom of ship, caused extensive flooding.

If she had a full load of 6" ammunition in her magazines - JB probably would have exploded on the first hit. As it was her only operational main turret was jammed, which probably would have put her out of action in a sea battle. The 7 hits were spread out over 45 minutes in two separate barrages - firing resumed when JB fired again.

[Gun Grape]

Thats the first reference that said 7 rounds, one of those a ricochet off the dock.

So it was a hit but could not be used as an example of good gunnery;)

Either way, and I'll accept 7 hits. Over 200 rounds fired against a ship that was tied up to the dock. At 200 rounds thats somewhere around 3.5% accuracy.

Which backs up my assertion that, except for a point blank shoot out, luck plays a bigger part than the type of range finder or any deceptive measures that were used.

As an end note it was aircraft from the Ranger that finally silenced the JB

[blidgepump]

Just wondering...

GG;

An earlier thread offered the chance to question what is considered good shooting in the Navy for large guns (i.e. 8-inch and larger)

As I'm still looking for that answer, I have at least learned that you consider 3.5% accuracy "A Poor Score" and I offer no argument.... :)

[Pacfanweb]

Question about the JB: When was she "sunk"? By Mamie's shells, or by bombs a couple days later?

[USSWisconsin]

Question about the JB: When was she "sunk"? By Mamie's shells, or by bombs a couple days later?

That is sort of subjective, since the berth she was in wasn't very deep, she never went under water, her weather deck was above water with her keel on the bottom. Her stern touched bottom after flooding from the 16" hit aft, and the first 16" hit knocked out her generators -reducing her pumping ability.
But the damage that really made sure she couldn't be fixed and open fire again was from dive bombers. The French had managed to fix turret one after it was jammed by a 16" strike. The first round with 500# bombs did significant damage, but not much more than the 16" shells, but the second strike with 1000# bombs pealed her decks back like a can opener -- they couldn't just hammer them down and open fire again. Most sources say the air strikes finally put her out of action.