Tactics Tank cannon lateral correction

[Mormegil]

Someone in the forums mentioned this as a bug in the T-34: The shot lands to the left of the aim point by a meter or so. Just to clarify, this isn't the 10-20 meter / tank length aim off bug.

Turns out it's not a bug, but a historical sort of parallax error. The lateral tank sights were zeroed to about 300 meters (or could be in real life, and are in game). That means at 300 meters, the shot lands right where the vertical cross-hair lands. Closer than 300 meters, it lands to the right, and further, it lands to the left.

So take that into account when aiming at tanks further out. A bit of geometry tells us, since the sight is offset about 20cm (I think), at 600 meters, aim point will be 40cm (almost half a meter). So take that into account when aiming for that ammo box.

In the first image, you can see the aim point in green, and the hit point in red on a tank at over 600 meters away.

You can see in the second image I'm uploading, the shot crosses the vertical line. If the sights and gunbore were perfectly parallel, the shot would only approach and never quite cross the center-line.


Note, this is true for both tanks.

 

[Vesper11]

Source? Why does it says zero when its actually at 300m? And considering that average range for tank combat was 500m why was it set at 300m (which is pretty close to 500m meaning that its going to be below 300m pretty soon)?

 

[Mormegil]

Source? Why does it says zero when its actually at 300m? And considering that average range for tank combat was 500m why was it set at 300m (which is pretty close to 500m meaning that its going to be below 300m pretty soon)?

Source is a PM from Alan Wilson. I asked him about it, as I thought it was a bug, and reported it in the bug section.

I'm not sure what you mean that says zero. The range only adjust the elevation, and on these tanks have no correction for lateral aim (left / right), so adjusting the range makes no effect on the lateral aim. Alan Wilson mentioned most tank gunners ranged it to about 300m.

 

[Vesper11]

NVM, I was confused by the screenshots.

 

[Jippofin]

All due respect, but the Russian engineers are not and were not idiots. Lateral error is extremely easily corrected mechanically on huge machines like tanks. I do not know, but I do not believe that tank designed at the eve of the second world war wouldn't have it's sight compensated for lateral error.

It is like making a car and leaving the steering wheel out.

 

[Mormegil]

All due respect, but the Russian engineers are not and were not idiots. Lateral error is extremely easily corrected mechanically on huge machines like tanks. I do not know, but I do not believe that tank designed at the eve of the second world war wouldn't have it's sight compensated for lateral error.

It is like making a car and leaving the steering wheel out.

This was not an error, and I'm not implying Russian engineers were idiots. The tank sights were purposely zeroed in at 300 meters laterally by the gunners.

I would assume there was no mechanism to rezero the lateral cross-hair tied to the range adjustment, which just changed the elevation cross-hair.

Either way, you can see for yourself the tank shot clearly crosses the center-line. If the gun bore and gun sight were perfectly parallel, this wouldn't happen (assuming no wind).

 

[Jippofin]

I would assume there was no mechanism to rezero the lateral cross-hair tied to the range adjustment, which just changed the elevation cross-hair.

Question is, why would you assume that? Lateral correction is simple to make and the lack of severely reduces the efficiency of the main armament of the tank by adding unnessecary variable.

Why wouldn't the engineers do a sight with lateral correction?

 

[Mormegil]

Question is, why would you assume that? Lateral correction is simple to make and the lack of severely reduces the efficiency of the main armament of the tank by adding unnessecary variable.

Why wouldn't the engineers do a sight with lateral correction?

I'm not talking about the cross-hair. I'm talking about where the sight itself is pointed. Making that adjust based on the range would require another entire mechanism. Since it's only 40cm off at 600m, it probably wouldn't have been considered a priority.

The reason I'm assuming there was no mechanism for it is because Alan told me they had to be manually zeroed, and were often done so at 300m.

Anyway, whether you believe it or not, it happens in game. You can choose to ignore this effect, or you can choose to take it into account when shooting.

 

[Jippofin]

Based on T-26 commanders tales of cutting single trees by shooting cannon shells at them at will I tend to believe their sights were laterally corrected.

T-34 optics were to be used to distances up to 3-4 kilometers. What is a "only" 40cm off at 600m will be 20 meters(!) off the mark at 3km. Do you think that is acceptable accuracy for tank main gun? The fact that it is in the game makes me only believe that the game is incorrect.

I know from personal experience that a bit more modern tank cannons are not affected by lateral error. Sighting in distance makes no difference in this. And of course cannons, just like all projectile weapons, have to be manually zeroed. Point is: range adjustment not only moves the sights up & down but also compensates for the horisontal convergence so that the round actually hits the reticle in the given range. Otherwise it would be rather useless, or wouldn't it? We would actually roughly zero in the cannon at 50m and then just confirm on range and fine tune.

Lateral error is actually quite significant. Easiest way to see this is to look at T-72 reticle, as the coax-mg was not corrected laterally. Look at the picture:
[url]http://www.kotsch88.de/feuerleit/t-72/tpdstrich1-2.jpg[/URL]
You will see small arrow heads under the main reticle with numbers 0.5 -18 under the main t-shaped reticle. These represent the points were the coax mg will hit from 50-1800 meters. 50 is right from the red lasing circle, and the 18 is way down on the left side of the sight centerline.

Leaving that kind of error in the sights when simple fix is available (turn the sight or move the reticle sideways according the ranging wheel), I don't think so.

 

[Vesper11]

Its even simplier to fix if you tilt vertical line a bit sideways, thus even if only the horisontal line moved the gun remained accurate. Its kinda hard to believe that there was no fix like that. What soviet engineers lacked in technology they made up in design.

edit: Alan Wilson, you did a very very bad job with t-34, shame on you!
p.s. Also 5 canister rounds missing.

 

[Field Marshal Rommel]

Source is a PM from Alan Wilson.

That is not a primary source.

 

[Vesper11]

http://www.pro-tank-t34.ru/tankovyj-periskopicheskij-panoramnyj-pricel-pt-4-7/

Thats a commanders periscope on T-34. Look at 9 and 11.
9 — маховичок механизма боковых поправок; (lateral correction mechanism handwheel)
11 — маховичок привода механизма углов прицеливания; (angle aiming actuator mechanism handwheel)


Alan Wilson, NKVD would've shot you on sight you german spy!

p.s. google translate the whole page if you want, its quite accurate.

 

[Mormegil]

That is not a primary source.

Umm, this is a primary source for In-Game, since he decided to put this into the game. This is the RO2:HOS Tactics section, not the history forum.


BTW: The same effect happens with the Panzer IV.

Personally, I preferred it in RO1, where they were parallel.

 

[Amizaur]

I'm sure there were some "official" ways of adjusting the sights that were taught.

On the other side, what would prevent a tank commander/gunner from adjusting THEIR sights as they wanted them? Zeroing for example on 1000m or just in infinitum (pararel to the gun) ?

And from numerious soldier memories, seems for me this is what they did. They adjusted the sights in a way they preferred or in a way that was comfortable/easy for them. At least the experienced crews and if the vehicles were not iterchanged between crews.

What's the point of having the sight zeroed and point-accurate on 300m but having an error on longer ranges ? As someone said, 60cm error for 600m means 120cm on 900m, 150cm on 1200m and so on. Isn't it much more simple to have ONE single 60cm error on all angles, just remember to aim 60cm left from intended aimpoint ?

What I would ask for, would be:

The T-34 co-axial MG to be fixed. It should fire along the main gun, and currently it fires way down.

Currently the axis of T-34 tank gun optics is same as barrel axis. But but the aiming marks are above the center. So the gun - thought the barrel is visibly pararel to the sight axis - is forced to "fire upwards" so it "can hit" where the 0m aiming marks are.

The MG seems to fire just straight so it fires way down, along the sight axis. I hope this will be fixed and the MG could be used to help rangefinding and - well, shot the infantry.

They way I would fix it would be to remove the "addedpitch" from the shell, and instead rotate the optics axis down by the same amount.
Tried this correction before - in previous game - and worked great.
Now not the sight center, but the upper (0m) aiming marks would be pararel to the gun, so the gun could actually fire straight and hit where the aiming marks are pointing. As the range increases and the shell drop is increasing, the lower marks would show where the shell is going to land.

Also because of currrent system, changing the range setting on the tank sight actually changes the angle at which the tank gun shells are shot :| Some angle values are added to shell launch-angle for each range setting. One cant' - like in real life - observe where the shell has landed and estimate the range using the aiming mark and range scale. Because the range scale doesnt' reflect shell ballistics. After changing the range setting and firing another shell, it will fly different trajectory ! Even though the gun barrel was not moved at all.

Would be much better and realistic to simply re-do the sight reticle texture so it just reproduced the in-game shell ballistics. This is the way the sights are really done. The sights has to reflect shell ballistics - not the other way (shell ballistics corrected to reflect the sight texture).

Then there would be no range-dependant shot-angle corretion needed. Much more simple AND realistic. Just move the horizontal marks on the sight texture to proper places - some pixels up, or some pixels down - so they reflect the shell ballistics.
I'm planning to do it, when the texture export feature is available and some tank-range map too...

Regards

P.S. Also pleeeeaaaase make more range settings for T-34 ! Make it possible to set range every 100m up to at least 1000m (2000m would be better).. Now my target is very often "in between" with big defference between both...
You don't have to change the texture, the aiming mark can stop between range marks, after all...
Or do it just with "smooth" regulation - as they really were . Press the button to smoothly increase, or decrease ;P

 

[Mormegil]

What's the point of having the sight zeroed and point-accurate on 300m but having an error on longer ranges ? As someone said, 60cm error for 600m means 120cm on 900m, 150cm on 1200m and so on.

Just to be pedantic, it's 20cm offset per 300m range. So 120cm would require 1200m range.

Isn't it much more simple to have ONE single 60cm error on all angles, just remember to aim 60cm left from intended aimpoint ?

I completely agree - except it would be 20cm, which is even better. That's how it was in RO1, and I found that to work quite well.

The T-34 co-axial MG to be fixed. It should fire along the main gun, and currently it fires way down.

I believe that's a bug with the rendering of the tracers, that was fixed, but seems to have come back in the later patches. Instead of looking at the tracers, look for the bullet puffs. Either way, the ballistics of the MG rounds can differ from the tank shot being used. Hence, the separate MG range marks (which you can't select).

Also because of currrent system, changing the range setting on the tank sight actually changes the angle at which the tank gun shells are shot :| Some angle values are added to shell launch-angle for each range setting. ...
Then there would be no range-dependant shot-angle corretion needed. Much more simple AND realistic. Just move the horizontal marks on the sight texture to proper places - some pixels up, or some pixels down - so they reflect the shell ballistics.
I'm planning to do it, when the texture export feature is available and some tank-range map too...

I think you may be confused with RO1 (T-34/85 and German tanks). In RO2, changing the range merely moves the horizontal cross hair up and down on the T-34, and the targeting reticule on the Panzer IV up and down. It doesn't move the gun at all. If you don't adjust the elevation of the gun, the shot lands in exactly the same place.

 

[Amizaur]

If it's 20cm then my mistake

As for different MG and cannon shell ballistics - I am aware of that. Still up to let's say 600m MG could be used to judge distances and aim the tank gun.

Here are ballistics of 76mm shell fired from ZIS-5 gun (ballistics same as F-34), and DT tank machinegun, taken from original Polish tank crew training manual printed in 1947, the data I believe was taken from Russian tank manuals and ballistic tables:

ZIS-5 gun, AP projectile (not specifically named), V0=662m/s (somewhat different than 655m/s used in RO2).
left is AP shell for ZIS-5 gun, right is obr. 1908 bullet fired from it's co-axial DT tank machinegun.

..76mm.AP.shell.662m/s.........7,62mm.bullet.840m/s

RNG......Vel........drop..TOF....RNG.....Vel........drop....TOF...

0m......662m/s...0,0m..0,0s...0m......840m/s...0,0m....0,0s
100m...651m/s...0,1m..0,1s...100m...758m/s...0,16m..0,13
200m...641m/s...0,4m..0,3s...200m...658m/s...0,44m..0,26
300m...631m/s...0,8m..0,4s...300m...605m/s...0,88m..0,42s
400m...621m/s...1,6m..0,6s...400m...539m/s...1,68m..0,60s
500m...612m/s...2,8m..0,7s...500m...481m/s...3,04m..0,80s
600m...602m/s...4,0m..0,9s...600m...431m/s...5,2m...1,02s
700m...593m/s...5,6m..1,1s...700m...390m/s...7,6m...1,26s
800m...583m/s...7,2m..1,3s...800m...357m/s...11,2m..1,52s
900m...574m/s..10,0m..1,4s...900m...330m/s...16,4m..1,8s
1000m..564m/s..12,8m..1,6s..1000m..308m/s...23,2m..2,11s

1500m..519m/s..32,0m..2,6s...1500m..236m/s..92,0m..2,82s

2000m..478m/s..64,0m..3,6s...2000m..---m/s.....---m..3,6s

(The Drop is calculated as 4x maximum height of trajectory - which is given in tables rahter than drop - and it's rather approximate as the values in tables were rounded to nearest 0.1)

as you can see, up to 500m there is no big difference between both trajectories (diference lower than 20cm), it starts to increase after 500m (the MG bullet losing speed and dropping much more), at 600m the difference being 1m, at 700m - 2m, 800m - 4m, 900m - 6.5m, 1000m - 10m

HE shell for ZIS-5/F34 is listed in those tables with V0 = 680m/s - so the same like in RO2.

I think you may be confused with RO1 (T-34/85 and German tanks). In RO2, changing the range merely moves the horizontal cross hair up and down on the T-34, and the targeting reticule on the Panzer IV up and down.
It doesn't move the gun at all. If you don't adjust the elevation of the gun, the shot lands in exactly the same place.

Well, I have observed it in the game and was quite sure what I'm seeing. That changing the range setting changes the shell trajectory in T-34. So I've assumed that the shell/sight code is similar as in RO1. Checking to be sure.

Hm, indeed - in T3476_AP code there is no "angle correction for given range setting" table anymore... I'm confused.

P.S. Everything is fine, the table was just moved elsewhere but it's still in the code. Every range setting launches the shell at slightly different angle, so it is "compatible" with the range scale texture.
Well, I would do it the other way - make a sight texture that reflects shell ballistics - but it's just me .

It doesn't move the gun at all. If you don't adjust the elevation of the gun, the shot lands in exactly the same place.

Check it in game, please. Mine shots doesn't. In T34 only.

PzIV doesn't need this correction as there is no "fixed" range scale on the texture. German tank sight works great and in a proper way. It's only not very fortunately zeroed too .


edit: In game velocity profile for T3476 and PzIVF2 AP shells. I cant' measure them in RO2 now, so I measured them (setting all important parameters like speed and BC the same) in RO1. Now IF the RO2 native ballistics are same as in RO1, then:

PzIVF2 T-34/76
BC 1,8 1,55

Range Velocity Velocity

0 740,0 655,0
100 723,2 636,7
200 706,7 618,9
300 690,7 601,6
400 675,0 584,8
500 659,6 568,4
600 644,6 552,5
700 629,9 537,1
800 615,6 522,1
900 601,6 507,5
1000 587,9 493,3
1100 574,6 479,5
1200 561,5 466,1
1300 548,7 453,1
1400 536,3 440,4
1500 524,1 428,1

It's somewhat different than the profile in ballistic tables above. The shells here are slowing down noticeably faster than they should. And the actual impact speed is used for penetration calcs in RO2.

Instead of using square of it... but that's another story. I believe the ballistics engine is still in developement phase and much of fine tuning is going to take place, after other more critical issues are resolved.

 

[Mormegil]

Check it in game, please. Mine shots doesn't. In T34 only.

Checked it, and I stand corrected. It's odd, both the horizontal cross-hair moves, AND the gun bore angle apparently moves. I found if I targetted the top of a building, lifted my mouse, and fired hitting the building, if I increase the range, the cross-hair moves down, but without moving the mouse, the shot now sails over the building.

 

[[TW]Wilsonam]

Amizaur is back

Well, quite likely there is some "fine-tuning" to do on the gunnery. There are still reports of some anomalous performance - not just worrying about the zeroing of the sights.

But I'm much more comfortable about the penetration calcs this time around. As always, there is huge potential for debates on the base data, of course...

 

[Field Marshal Rommel]

But I'm much more comfortable about the penetration calcs this time around.

Then explain why the PTRS is penetrating through the front turret of the T34/Panzer at +200 meters.

 

[Amizaur]

Hi Wilsonam

Yes, IMO the current ballistics system is a HUGE improvement over the RO1 system.
A good start - every important parameter is really used in the system now.

So it's absolutely possible to fine-tune it with small code / stats modifications to make it work very nicely .

It's more of "what one want's to have" (I mean "proper" penetration ranges and probabilities, behaviour) than "what is possible to have".

Regards!