TDC updating newbie question

[Zosete]

Hi there. Been watching this forum for years, and finally I decided to try GWX as my first SH3 experience.

I play with manual targetting but I haven't unchecked the WO yet to compare my measures to the accurate data.

I don't understand how the TDC updates. I make all my calculations on the map and enter them manually. The notepad is too cumbersome for me and the speed values it returns are always way off...

I set the values, then I turn the TDC auto on again. The target is locked in my uzo/periscope... but the values don't change. Sometimes the AOB updates itself (poorly), but the distance meter always remains the same.

What am I doing wrong? The only thing I set on the notepad is the ship type, just in case. Do I need to have some values set on the notepad? I've read the manual and it recommends entering yourself the data in manual targetting.

As it stands right now, the only method for me is making calculations just before firing. Everything I set in advance is a waste of time and another chance for the target to spot me. I'm sure I'm doin' something wrong. I've tried going back and forth to the periscope with a lock on the ship, but nothing.

Thanks in advance.

[Aktungbby]

Zosete! a long silent run!

[Jimbuna]

If you enter the data in manual targetting you can have officer assistance enabled to help check your calculations.

[BigWalleye]

Originally Posted by Jimbuna

If you enter the data in manual targetting you can have officer assistance enabled to help check your calculations.

If I understand correctly, the OP wants to know why the U-boat's "TDC" doesn't update position like the TDC on an American sub does. If that is the question, the answer is that the German version (called a TVR) doesn't have a Position Keeper function, as the American TDC does. It won't update target position. The TVR will calculate lead angles though, which the TDC doesn't do. They are two similar, but different boxes.

[Zosete]

. It won't update target position. The TVR will calculate lead angles though, which the TDC doesn't do.

Thanks. So it only updates AoB? That's not a big incentive to put the TDC in auto. You might as we'll leave it in manual position. But both the SH3 and GwX faqs and docs insist on turning auto back on once you've entered the data. How does this exactly work?

[Zosimus]

Originally Posted by Zosete

Hi there. Been watching this forum for years, and finally I decided to try GWX as my first SH3 experience.

I play with manual targetting but I haven't unchecked the WO yet to compare my measures to the accurate data.

I don't understand how the TDC updates. I make all my calculations on the map and enter them manually. The notepad is too cumbersome for me and the speed values it returns are always way off...

I set the values, then I turn the TDC auto on again. The target is locked in my uzo/periscope... but the values don't change. Sometimes the AOB updates itself (poorly), but the distance meter always remains the same.

What am I doing wrong? The only thing I set on the notepad is the ship type, just in case. Do I need to have some values set on the notepad? I've read the manual and it recommends entering yourself the data in manual targetting.

As it stands right now, the only method for me is making calculations just before firing. Everything I set in advance is a waste of time and another chance for the target to spot me. I'm sure I'm doin' something wrong. I've tried going back and forth to the periscope with a lock on the ship, but nothing.

Thanks in advance.

Well, the distance meter doesn't auto-update, but that's not generally a problem as even extremes of distance only make at most a 1 degree difference in the firing solution.

Most people set up their firing by going ahead of the ship and lying in wait at an exact 90º angle facing the ship. To do so you must determine the ship's course and speed. If you have map updates on, that's fairly simple. Once you are within sight of the ship you can zoom in all the way and use the drawing tools to drop an x on the stern of the ship. That can take some practice to do effectively, but once you've got the hang of it you can get it working easily.

From there hit O and start the stopwatch. Then go back to the map screen (F5) and pull the stopwatch part down from the top (the little brown section) and you'll be able to observe the ship as it moves. I recommend that you time the ship for 6:28.8 seconds and then measure the distance it has moved. You can also draw a line from the mark you put through the bow of the ship and it will tell you the ship's course. Multiply the distance the ship has traveled by 5 and you'll have its speed.

Then proceed away from the ship and ahead to where you can set up the firing solution. Submerge and creep slowly ahead until you're at a good range (maybe 1km is about right) from the line you've drawn. Turn the observation scope until the gyroangle reads 000 (make sure the target speed is set to 0 before you do this) and that will be the true 0 of your periscope. Then go back to the TDC (F6) and set AOB 90º port or starboard, depending, set the ship's speed, range to the ship when it passes you, and all the data.

I normally set for impact torpedoes at 4 meters depth. Others try to ID the ship and set the torpedo to underrun it with magnetic triggers. I've never had success with that, and historically, it seems the Germans didn't either.

[Zosete]

I think I'm not getting through... I know how to get into position and get all the data I need with a protractor in 5 seconds. I can even get a one hit KO with a magnetic pistol 1 meter under the keel.

My question is how does the ¿vorkschaffel?? Auto update system works. Exactly. Does it only get AoB? Do you need to have the ship
Locked? Do you need to switch to f3/Uzi view to get the update?

And the most important one: is there any intersection point in the torpedo trajectory as shown on the map? when should I fire?

I dont wanna limit Myself to 1.000 meter range shots in perpendicular, I want to try Hail Marys from afar and I'm not sure if the TDC takes into account everything so you can fire anytime as long as the calculations are right (and gyro is low) or you have to choose the timing.

[BigWalleye]

Originally Posted by Zosete

I think I'm not getting through... I know how to get into position and get all the data I need with a protractor in 5 seconds. I can even get a one hit KO with a magnetic pistol 1 meter under the keel.

My question is how does the ¿vorkschaffel?? Auto update system works. Exactly. Does it only get AoB? Do you need to have the ship
Locked? Do you need to switch to f3/Uzi view to get the update?

And the most important one: is there any intersection point in the torpedo trajectory as shown on the map? when should I fire?

I dont wanna limit Myself to 1.000 meter range shots in perpendicular, I want to try Hail Marys from afar and I'm not sure if the TDC takes into account everything so you can fire anytime as long as the calculations are right (and gyro is low) or you have to choose the timing.

For a "normal" ( near 90 degrees) attack, the range does not matter. To use the TVR, select manual input. Enter the target speed and the projected AoB at torpedo impact. (For the normal attack, that will always be 90 port or 90 starboard. Make sure you enter the correct one!) Don't even bother with the range dial. Turn the scope to zero bearing. (Or to 180 if you are firing a stern tube.) Engage autoupdate. Now move the scope so the gyro angle is zero. When the part of the ship you want to hit is directly under the vertical wire in the scope, press "Fire!" If you are properly set up, the torpedo will run straight and strike the target at the aim point.

Of course, the closer you can get to the target, the better. Just stay outside the torpedo arming distance (about 300 m).

The farther from 90 degrees your setup is, the more important range becomes. So get as close as the situation and the escorts will allow, because that minimizes the effect of range errors.

The lead angle calculation is not essential. But it is nice to have.

[Zosimus]

Originally Posted by Zosete

I think I'm not getting through... I know how to get into position and get all the data I need with a protractor in 5 seconds. I can even get a one hit KO with a magnetic pistol 1 meter under the keel.

My question is how does the ¿vorkschaffel?? Auto update system works. Exactly. Does it only get AoB? Do you need to have the ship
Locked? Do you need to switch to f3/Uzi view to get the update?

And the most important one: is there any intersection point in the torpedo trajectory as shown on the map? when should I fire?

I dont wanna limit Myself to 1.000 meter range shots in perpendicular, I want to try Hail Marys from afar and I'm not sure if the TDC takes into account everything so you can fire anytime as long as the calculations are right (and gyro is low) or you have to choose the timing.

Have you read http://www.subsim.com/radioroom/showthread.php?t=206381 ?

[Pisces]

Originally Posted by BigWalleye

For a "normal" ( near 90 degrees) attack, the range does not matter. ...

Sorry, a 90 degree set up has nothing to do with range settings becoming meaningless. It is the gyro angle being 0 (or close to it) that makes the range setting become meaning less. If the torpedoes do not have to turn (gyro = 000), then the TDC does not have to account for the parallax angle that develops when the torpedo does need to turn and and sees the target from a different approach angle at the end of the turn.

As an aside: Parallax is the situation where you see a close object at a different direction (different things on the background horizon) than a person standing 10 meters or yards away. And is (part of) the means how your eyes perceive distance at close range. Your eye balls turn towards each other to aim at the object in focus. Your brain does the triangulation.

It might be that in this 90 degree setup you choose, by default, to wait until the target is almost in front of you. And therefore get the gyro-angle to be close to 0. But it isn't the differences in own course and target course that makes the difference in chances of hitting. Try firing at the target when your boat is aligned parallel to the target course and it comes to the bearing of 270 or 90. (which is also what the gyro angle will be close to) As you fire to your port or starboard side, you might get a hit. But it won't be the point on the hull that you aimed for at different distances. You will expect this to happen if the torpedoes move straight ahead out of the tubes. If the torpedoes need to turn, close distance makes it worse.

Ever wondered why torpedoes tend to miss when you fire too late or early? The target is on a bearing far away from dead ahead, and the distance is close. This enhances the correction that the torpedoes need to make for the parallax deviation. If the range is still from an older moment and thus further away, the torpedo is not properly aimed.

[Pisces]

Originally Posted by Zosete

I think I'm not getting through... I know how to get into position and get all the data I need with a protractor in 5 seconds. I can even get a one hit KO with a magnetic pistol 1 meter under the keel.

My question is how does the ¿vorkschaffel?? Auto update system works. Exactly. Does it only get AoB? Do you need to have the ship
Locked? Do you need to switch to f3/Uzi view to get the update?

While I do of course not know what exactly goes on in the code, I think I have a fair grasp on how it functions to us TDC users.

Locking a target is not necessary for the TDC to work. That is to say, IT IS needed for the notepad method to work. But not to make the torpedo calculations based on your dialed in inputs in the F6 TDC page. The game needs to match the mastheight in the recognition manual with the observed target in front to calculate range with the stadimeter. It could have been done differently, but Ubisoft decided this was the way it had to be done. As the game cannot recognise shapes in the view, the game relies on you to point at a 3d model select it by locking. Allowing the chosen mastheight to be applied for the range calculation. Also, when calculating speed, it needs to measure how much the periscope changes bearing as it follows. So it makes this easy for you by locking on the 3d model center. From this small turn, the initial range, and the AOB you have put in, it calculates the distance the target moved and in how much time. From those last 2 you get a speed. But it al starts with how accurate the range measurement and AOB was. However, I digress with notepad method info.

The Auto update mode of the TDC means that as you rotate the periscopes/UZO, the TDC also updates the AOB in the same step. The periscopes/UZO are directly linked to the bearing dial. That means that when you look at different targets in a convoy for example (which could be in all directions around you), the TDC has the same instantaneous course for all things it looks at. If it didn't you would have to manually correct each for change in bearing. As all targets in a convoy or small group move in the same direction with the same speed (if you go by unnoticed), this is very user friendly.

It does not update the distance to the target. It keeps and uses the last entered distance, or the last Stadimeter measurement you sent with the notepad, to account for torpedo turns at close range. Why it does not update the range? Good guess. No idea myself. I am not familiar with the real world German TDCs to know if they had this feature.

As explained in my previous message above, it's of little importance anyway if you let the torpedoes go at the target straight ahead out of the tubes. But you can't always force the tactical situation to your desires, and sometimes you must account for large gyro angle turns at close range. As a secondary use of this dial, it is probably used to calculate the impact timer on the stopwatch after you fire a torpedo. I have never tested this though if this is as accurate as you enter it, or if the game calculates it anyway by cheating with unit coordinates in the world. But I wouldn't call this a required part of it's functionality to get the torpedoes on target. It's made to make your life easier finding out when, and build up suspense.

When you input the target speed (and torpedo speed setting) and the AOB, then the TDC has enough information to calculate the rough lead angle getting the torpedoes towards a moving target. It is of course based on the periscope/Uzo looking towards the target. It calculates how much the torpedo needs to turn away from the periscope view to get onto the target in the future. So you do not have to set the bearing manually in the F6 TDC screen to do that. Or wait a few seconds to get the proper timing. Just look at it when you want to fire. Point on the hull where it needs to hit. It can be that accurate if all is done well.

It also does this correction for the actual torpedo trajectory right after leaving the tube. The parallax thing. The end result is the gyro angle that you see near the notepad. This is the angle that the torpedoes turn to finally. Aside from the range changing as the target approaches or recedes, the updates happen instantaneously while you move the periscope. This is quite a nice feature in the heat of battle. As that means several things less to worry about. And when you have to think while under pressure, mistakes start to spawn. Automation definitely helps.

Why you cannot see the settings change? There might be a hidden bug in the game, or only in some TDC Gui mods that make the TDC get stuck after some unknown event. The following might not apply to your mods selection, but who knows, it might help. For example, it was noticed in the OLC gui mod that the TDC dials and iirc the Attackdisk dials (a rotating bearing-course-AOB conversion wheel feature based on a real sliderule disk) in the 2D user interface got stuck after some unidentified cause. Dragging the dials just wouldn't budge. The solution however was simple. Go into the 3D command room, and go to the TDC station. On the side panels near the floor there is a 3D red button with the same function as the Auto-Manual TDC button on the F6 page. Flip it, and the TDC/Attack disk becomes unstuck again. Something unknown causes the 3d button and the 2d button to go out of sync jamming the device inoperative.

Try it and see if it helps.

And the most important one: is there any intersection point in the torpedo trajectory as shown on the map? when should I fire?

I dont wanna limit Myself to 1.000 meter range shots in perpendicular, I want to try Hail Marys from afar and I'm not sure if the TDC takes into account everything so you can fire anytime as long as the calculations are right (and gyro is low) or you have to choose the timing.

You fire when you want to! The TDC steers the torpedo to the future position of the target when you hit the button. The torpedo will meet the target, assuming all data that you have put in is correct. And it doesn't change course or speed of course. Also, the tubes must be opened previously, so it doesn't have to do that for you and cause a delay. Whether or not you hit, is often the question if the chosen time and situation was right to make best use of things working in your favour. As your settings can never be totally perfect, and you must account for errors. When to fire? The game cannot tell you that. That is your tactical decision. It does have the infamous green/yellow/red triangle , but that is a meaningless indicator of bearing (or gyro angle, I'm not sure. it's hard to distinguish between them in terms of color coding.) It says nothing about the probability of hitting it.

The TDC F6 page does show a prediction of the torpedo path, and assumed impact point (based on set range). But depending on the realism/difficulty settings, you might not get the target itself shown. So it might be of little use, as you can't plot in that tactical map. It's a different map, it's separate from the navigation map.

Hitting the target in it's flank and up close and personal has the least chance of missing it because it shows it's broad side. At close range it's length gives the most margin for error on the lead angle of the torpedo. Allowing for misjudgement in target speed and AOB or distance. Far away, head on or tail AOB requires much more accuracy in the inputs to make a hit. You have to get yourself into situations (position and orientation) that give the best odds and wait until the best time comes.

[BigWalleye]

Originally Posted by Pisces

Sorry, a 90 degree set up has nothing to do with range settings becoming meaningless. It is the gyro angle being 0 (or close to it) that makes the range setting become meaning less. If the torpedoes do not have to turn (gyro = 000), then the TDC does not have to account for the parallax angle that develops when the torpedo does need to turn and and sees the target from a different approach angle at the end of the turn.

As an aside: Parallax is the situation where you see a close object at a different direction (different things on the background horizon) than a person standing 10 meters or yards away. And is (part of) the means how your eyes perceive distance at close range. Your eye balls turn towards each other to aim at the object in focus. Your brain does the triangulation.

It might be that in this 90 degree setup you choose, by default, to wait until the target is almost in front of you. And therefore get the gyro-angle to be close to 0. But it isn't the differences in own course and target course that makes the difference in chances of hitting. Try firing at the target when your boat is aligned parallel to the target course and it comes to the bearing of 270 or 90. (which is also what the gyro angle will be close to) As you fire to your port or starboard side, you might get a hit. But it won't be the point on the hull that you aimed for at different distances. You will expect this to happen if the torpedoes move straight ahead out of the tubes. If the torpedoes need to turn, close distance makes it worse.

Ever wondered why torpedoes tend to miss when you fire too late or early? The target is on a bearing far away from dead ahead, and the distance is close. This enhances the correction that the torpedoes need to make for the parallax deviation. If the range is still from an older moment and thus further away, the torpedo is not properly aimed.

Sorry if I confused you with my use of the word "normal." Apparently you are not familiar with the mathematical use of "normal" meaning "perpendicular to." A normal attack is an attack perpendicular to the target track, specifically to achieve a zero gyro angle.

Your lengthy discussion of "parallax" is perplexing, as parallax is only a small part of the fire control problem. A Typ VII U-boat had an LOA of 67 m, so if the periscope were set at about 2/3 of the length, the parallax correction at a firing bearing of 45 degrees would only be 1.9 degrees. At 2000 m, this reduces still further to a correction of only 0.8 degrees. At its maximum effect, at 90 degrees firing bearing, the parallax correction at 1000 m is only 2.6 degrees. At 1000m, a cargo ship of 140 m LOA subtends an angle of 8 degrees. So the impact of parallax is not going to spoil too many shots. And, since the parallax correction actually decreases with range, if parallax were a critical factor then it would follow that torpedoes should be fired at maximum range to minimize the effect of parallax error. I don't think I have ever heard that advice before.

EDIT:

Reread your post and realized there is further confusion over terminology. What you are calling "parallax" includes offsets due to parallax, but also those due to torpedo reach and torpedo turning radius.

From US Navy Submarine Torpedo Fire Control Manual, SLM-1, dated May, 1950:

121. PARALLAX CORRECTION TORPEDO TUBE:
The angular correction compensating for the longitudinal distance between the muzzle doors and the periscope. See Plate I, figure 4.

126. REACH:
The initial straight path of the torpedo, measured in yards. Symbol: M. (See Plate I, figure 3).

136. TORPEDO TURNING RADIUS:
The radius of the circular track, in yards, of the torpedo from the end of the initial straight path to the beginning of the final straight path. Symbol Z. (See Plate I, figure 3)

While torpedo tube parallax correction is small and can be ignored in practice, the reach and turning radius corrections are, taken together, quite significant.

I do not have historical data for the reach or turning radius of a WW2 German torpedo, but I have measured something more pertinent: the actual reach and turning radius of a Typ G7a as used in SH3. Reach is 90m, turning radius is 98 m. So for a 45 degree gyro angle, the offset is 280 m ontrack plus 30 m crosstrack.

[Zosete]

Specially to Pisces for that lengthy post. With everyone's suggestions and my in-game observations and rereading the FAQs I think I made my mind up on some things.

1. The only thing that gets auto updated is the AoB. For that, you need to have LOS. Periscope up suffices and lock is not necessary (but recommended).

2. You DO need to switch it back to automatic because the data you enter updates the torpedo bearing. Fundamental.

3. I should have realized before that the trajectorie is just for info. Once you get accurate data you could fire anytime for a perfect hit (of course, that's when the other variables factor in and you'd better choose the perfect split second).

Now I only have one question left. AoB is relative to course rather than ship angle, right? I mean: if i'm trying to catch a ship that it's zigzaging slowly in front of me, his bow swings wildly but the "average" course is relatively unchanged. I still don't get if the TDC is able to update AoB when the target changes its course. I reread your posts but I'm a bit puzzled about this.

[Sailor Steve]

Originally Posted by Zosete

Now I only have one question left. AoB is relative to course rather than ship angle, right? I mean: if i'm trying to catch a ship that it's zigzaging slowly in front of me, his bow swings wildly but the "average" course is relatively unchanged. I still don't get if the TDC is able to update AoB when the target changes its course. I reread your posts but I'm a bit puzzled about this.

AOB is the angle he sees you at. If he's heading directly toward you the AOB is 0. If his lookout would say "Periscope at 20 degrees!" then the AOB is 20.

[BigWalleye]

Originally Posted by Zosete

Specially to Pisces for that lengthy post. With everyone's suggestions and my in-game observations and rereading the FAQs I think I made my mind up on some things.

1. The only thing that gets auto updated is the AoB. For that, you need to have LOS. Periscope up suffices and lock is not necessary (but recommended).

2. You DO need to switch it back to automatic because the data you enter updates the torpedo bearing. Fundamental.

3. I should have realized before that the trajectorie is just for info. Once you get accurate data you could fire anytime for a perfect hit (of course, that's when the other variables factor in and you'd better choose the perfect split second).

Now I only have one question left. AoB is relative to course rather than ship angle, right? I mean: if i'm trying to catch a ship that it's zigzaging slowly in front of me, his bow swings wildly but the "average" course is relatively unchanged. I still don't get if the TDC is able to update AoB when the target changes its course. I reread your posts but I'm a bit puzzled about this.

The TVR updates AoB assuming the target sails straight ahead. If you estimate AoB based on target's base course, then the TVR will not know about zigzags. If you enter a new AoB when the target zigs, then the TVR's calculated deflection will be correct as long as the target remains on that course. Base course is useful to you for planning your approach, but it doesn't figure into the firing solution.