Oh no, not another manual targeting procedure!!!

[ronbrewer]

Hello everyone,

I've been playing SH3 on manual targeting ever since it came out in 2005 and have had my share of learning all kinds of manual targeting methods. Like a lot of you I started out with the 3:15 procedure and eventually started doing the collision course method using slide rules and whiz wheels that was posted about a year ago. However, in the last couple of months I've been doing manual navigation along with manual targeting and found out just how difficult it can be to get a good torpedo solution when you no longer have that GPS type of accuracy on the map that shows exactly where your sub is located. Reading through the different posts about the common behavior of Uboat approaches to a target I found the following themes:

1) The Uboat would do an end around using just the smoke on the horizon and then close in on a rough estimate of a collision course.
2) The Uboat goes to periscope depth as soon as the target's smoke stacks are seen since waiting any longer gives the enemy the opportunity to spot you from the bridge when it becomes visible on the horizon.
3) The sub was always in motion and never did the hummingbird affect that could make it pop up on the surface and spoil the stealth.
4) The hydrophone was used a lot more than the periscope to get into a good position to have the target's AOB 90 cross your bow.

It's at this point that different methods were used to determine the target's speed and true course (which is what I've read was entered into the German TDC instead of AOB). One procedure that I have found good success with is the right triangle method where the Uboat would use tables of numbers to determine speed based on a particular range covered.

Using the right triangle method means as you close in on the target you position your sub so that when the target reaches AOB 90 you have the target's bearing at 20 degrees (or 340 degrees if starboard of the target). You only have to take one range measurement at that moment in time and then start the stopwatch. The tables of numbers will have everything else for you once you get the time it takes for the target to reach a bearing of zero (cross in front of your bow). It also doesn't matter that your sub is moving during this time since you are basically traveling down the hypotenuse of the right triangle and it won't affect the time of the target to make it to a zero bearing. However, you do want to be going slow (around 2 to 4 knots) so that you remain hidden and so that you don't beat the target to the crossing point! Once you look up the speed on the tables you have everything you need for a firing solution. The target will be at AOB 110 when it crosses your bow and the range you took at AOB 90 is still good enough for an estimated torpedo impact time since your sub is moving down the hypotenuse. You can enter an AOB 110 on the TDC well before you start this procedure since you will position your sub to make it accurate. Below is a drawing of the sub and target's position and path of travel.



The steps for an attack are as follows:
1) Set up the TDC for AOB 110 (port or starboard depending on attack position).
2) As the target approaches AOB 90 get your sub in position to have it at bearing 20 degrees (340 degrees for starboard attack) when it actually reaches AOB 90.
3) Start the stopwatch and take a good range measurement. Lower the periscope since the 20 degree run may take a while.
4) Flip to the right table that is the closest match to your range measurement.
5) Enter the range into the TDC while waiting and use the hydrophone to see when the target is close to zero bearing.
6) Raise the periscope and stop the stopwatch when the target crosses your bow.
7) Find the closest match on the table for the seconds shown on the stopwatch and enter it onto the TDC. Open the tube doors.
8) Go back to periscope and swing it to the target that has passed your bow as you entered the speed.
9) Wait a second or two for the auto TDC to adjust to the new periscope bearing (not modeled in the game but was done in real life) and launch the torpedo!

For an example of the numbers used in one of my attacks:

1) Attack on the target's port side and had a range of 1172 meters at bearing 20 when target reached AOB 90.
2) Rotated the range dial to a little less than 1200 on the TDC.
3) Used the table for 1200 meters to calculate speed. The table shows the target will travel just under 436.76 meters since that equals tan20 * 1200.
4) Stopwatch displayed a little above 112 seconds so I chose a speed of 7.5 knots for the target (table had 7.51 knots for 114 seconds and 7.78 knots for 110 seconds).
5) Moved the periscope to about 354 degrees and fired the torpedo at the middle of the target (auto TDC adjusted to AOB 116).

I have the spreadsheet for ranges of 1000 meters up to 2900 meters. The formulas used are tan20 * AOB 90 range to get the distance the target will cover on short leg of the right triangle. And then distance covered / seconds * 1.96 to convert to knots. If anyone is able to host the file for downloads let me know and I'll pass it along. Below is a snapshot of the tables for 1000 meters to 1300 meters (may need to save it as a jpg to get the original size):



Like I said in the beginning, there are a number of manual targeting methods available and I've found that this procedure works fine now that I do manual navigation as well. Below is a list of pros/cons for this method:

Pros: Sub can always be on the move to maintain depth, no calculators or slide rules needed, AOB and range entered at leisure, not tied to game map.

Cons: Need accurate AOB 90 identification (one of the easier AOB's to identify since the bridge is square), need accurate range calculation, for fast moving targets you may need to do an end around after determining speed if you delay looking through the tables and entering speed on the TDC after the target reaches a zero bearing.

By the way, if you have to do an end around then to get the target's true course just subtract 70 degrees from your sub's true course (or add 70 degrees if you are starboard of the target). Since you have the speed and true course you can just come straight in for an AOB 90 attack after the end around, provided the target hasn't changed course and/or speed.

Hope this procedure helps some of you out. At some point in the near future I want to offer another spreadsheet I have that provides lead angles for torpedoes in case any of you want to simulate a defective TDC after depth charges or just to see how the WWI sub captains had to use the law of sine's to point their sub ahead of the target since gyro angles hadn't been designed yet.

Thanks,
Ron

[Heibges]

I use a similiar method to find range. I have a MILS chart which basically gives me instantaneous range.

I don't know how you guys calculate speed at the last minute without using Pause.

I generally use the matching speed method if I am on the surface. But this depends a lot on the visibility.

[jmr]

Heibges, would you mind sharing your MILS chart?

[CaptainAsh]

Originally Posted by Heibges

I use a similiar method to find range. I have a MILS chart which basically gives me instantaneous range.

I don't know how you guys calculate speed at the last minute without using Pause.

I generally use the matching speed method if I am on the surface. But this depends a lot on the visibility.

Periscope method : you have to be still and place your periscope on a static bearing. You have to know the exact length between two specific plots of your target (the easyest of course is the bow and the stern as identification book is giving you the ship length). Start your chronometer when the first point cross your crosshair and stop it when the second point cross the crosshair. Double the length and divide all by the amount of seconde. Here is your speed. The useful part is that the faster the ship is, the faster you get his speed
There s an issue though. The closer you re from the ship path, the closer it must be to have a good reading and if your right on his path you can't get any speed. It s really rare for me to be in that situation but it happens if you re shooting him from his own trail with magnetic pistol. Not such an handicap though cause the if your eels' path is the same as the target path, speed doesn't really mater, you will catch him sooner or later

[ronbrewer]

Originally Posted by Heibges
I use a similiar method to find range. I have a MILS chart which basically gives me instantaneous range.

I don't know how you guys calculate speed at the last minute without using Pause.

I generally use the matching speed method if I am on the surface. But this depends a lot on the visibility.

The tables already have the speed calculation done ahead of time. What you end up doing at the last minute is just finding the best match on the table with the seconds on the stopwatch and then adjusting the speed dial on the TDC in the conning tower before opening the tube and getting back on the periscope to launch the torp.

[Puster Bill]

Originally Posted by ronbrewer

However, in the last couple of months I've been doing manual navigation along with manual targeting and found out just how difficult it can be to get a good torpedo solution when you no longer have that GPS type of accuracy on the map that shows exactly where your sub is located.

I might be a little confused (wouldn't be the first time), but what difference does it make to your torpedo solution if you don't know exactly where you are? After all, for all intents and purposes when you are attacking the assumption is that your boat is the 'center of the Universe'. All target data is in relation to your boat, ie., range, bearing, AOB. Only target speed is independent of your position, but that is a scalar, not a vector.

So I'm not following why manual navigation would make targeting harder. It seems it would certainly make interception harder, but your procedure assumes the target has been spotted.

[Heibges]

Originally Posted by jmr

Heibges, would you mind sharing your MILS chart?

I had a complete chart but lost it. I was in the process of making a new one when I got really busy at work and stopped. Let me see if I can find it at home.

Basically what I did what make a single mission with a non-moving enemy ship. I got lined up at 90° angle, so I perfectly bisected the ship with my bow. TDC was automatic so I could see the exact range. I started at about 3000m away.

Using the scale on the UZO, I measured the length of the ship at a number of distances between 2400m and 400m.

After this I changed the enemy ship in the mission, and started over.

I'm not sure what the scale is on the UZO, but I called it MILS because I was familiar with that term. Each unit on the UZO is probably 5 or 10 mils.

Anyway, the chart looked something like this.

Ship..................1200m.........600m
C2 Merchant........6mils...........12mils
C3 Merchant........7mils............14mils

So if I measure the length of a C2 merchant, and it takes up 12 units in the UZO, I know the ship is 600m away.

[ronbrewer]

Originally Posted by Puster Bill
I might be a little confused (wouldn't be the first time), but what difference does it make to your torpedo solution if you don't know exactly where you are? After all, for all intents and purposes when you are attacking the assumption is that your boat is the 'center of the Universe'. All target data is in relation to your boat, ie., range, bearing, AOB. Only target speed is independent of your position, but that is a scalar, not a vector.

So I'm not following why manual navigation would make targeting harder. It seems it would certainly make interception harder, but your procedure assumes the target has been spotted.

Sorry about that. What I meant by manual navigation is that you use a transparent .tga file for your sub so it is invisible on the map. Some of the manual targeting procedures have you draw a couple of lines from the center of your sub to a specific range/bearing for a target ship. You can no longer do this under the manual navigation mod so I spent some time looking into a procedure that doesn't require the map and only needs one range snapshot. After reading about some of the geometry tables that were used by Uboat weapon officers (both WWI and WWII) I came across the right triangle procedure that has the sub slide down the hypotenuse during the speed calculation and doesn't require whiz wheels or slide rules for the last few seconds of the torpedo solution. Plus it allows you to manually turn the dials on the TDC in the conning tower (has always been one of my favorite parts of the sub simulation) without pausing the game and avoiding the notepad entries on the periscope screen that kind of take away part of the immersion for me.

Thanks,
Ron

[Canovaro]

Thank you for sharing, have to think about this a little.

[Maraz]

That's brilliant!

When do you exactly switch to auto TDC? After entering target speed?

It would be great having all the tables you made (have you tried filefront to upload the files?).

It would be interesting if you could share other methods and tables used historically.

Cheers
Maraz

[Puster Bill]

Originally Posted by ronbrewer

Sorry about that. What I meant by manual navigation is that you use a transparent .tga file for your sub so it is invisible on the map. Some of the manual targeting procedures have you draw a couple of lines from the center of your sub to a specific range/bearing for a target ship. You can no longer do this under the manual navigation mod so I spent some time looking into a procedure that doesn't require the map and only needs one range snapshot. After reading about some of the geometry tables that were used by Uboat weapon officers (both WWI and WWII) I came across the right triangle procedure that has the sub slide down the hypotenuse during the speed calculation and doesn't require whiz wheels or slide rules for the last few seconds of the torpedo solution. Plus it allows you to manually turn the dials on the TDC in the conning tower (has always been one of my favorite parts of the sub simulation) without pausing the game and avoiding the notepad entries on the periscope screen that kind of take away part of the immersion for me.

Thanks,
Ron

Ahhh, OK, that makes *MUCH* more sense now. I don't bother with the map view when in action, just for those long periods between contacts. Still, you could do a manual polar plot (like using a maneuvering board). I'm thinking about checking the bookstore where I work (a college) to see if they have some polar plot paper. That way I don't have to use an American maneuvering board to manually plot contacts.

By the way, Hitman is working on a whiz wheel/circular slide rule based on one that was actually used for targeting in U-boats during WWII. He's already made some good progress:
http://www.subsim.com/radioroom/showthread.php?t=113591

[ronbrewer]

Originally Posted by Maraz
When do you exactly switch to auto TDC? After entering target speed?

That's right. Once I adjust the speed dial on the TDC I click the button to turn the light red so that it will start updating the gyro angles based on periscope movement. I also open the tube doors right after this since all torp settings are done.

I didn't mention it in the original posting but I also configure the torpedo pistol setting, running speed, and depth during the target's 20 degree run while the hydrophone guy whispers the updated target bearings. Makes the atmosphere in the conning tower a little tense.

One thing I haven't found good info on, historically speaking, is when the weapon officer would open the tube doors. I've been going on the assumption that they should not open until all TDC input data is complete. I also found out the game doesn't let you shut them if you go below 20 meters when evading DD's so I keep them shut until right before firing. Though it's not modeled in the game open tube doors should reduce the sub's depth ability.

Also, thanks for the heads up on the Filefront website. The following link is has the spreadsheet for right triangle attacks:

http://files.filefront.com//;7409015;;/

And this link has the spreadsheet that computes lead angles based on AOB and torpedo impact times (for defective TDC simulation or WWI style solutions):

http://files.filefront.com//;7409021;;/

Both are in Excel format and on the second one just enter in different AOB numbers to get updated lead angles. You'll find the same angles for AOB 80/100, 70/110, etc. I just printed out each table and stapled them together in a booklet format. Basically what you do in the game is set the TDC button to a green light so the periscope swings freely and the gyro angles stay at zero. You then have to position your sub to provide the lead angles for the torp based on the target's AOB. For example, if you get on a perpendicular course to the target you know that it will be at AOB 90 when it crosses your bow. Let's say the target is going 9 knots and you have the torp speed set to 40 knots. The spreadsheet shows a lead angle of 13 degrees needed for these speeds so you would turn the sub 13 degrees to the left (or right for a starboard attack) and then turn the periscope back to a 13 degree setting (or 347 degrees if starboard) and fire the torpedo when target's center reaches a bearing of 13 degrees (AOB 90). The torp will run staight ahead due to zero gyro angle and range really won't come into play. However, if you do a range check you can use the second tab of the spreadsheet to get an estimate of the torpedo impact time.

After doing this on a few patrols I really learned to appreciate that TDC!!

Thanks,
Ron

[ronbrewer]

Originally Posted by Puster Bill

By the way, Hitman is working on a whiz wheel/circular slide rule based on one that was actually used for targeting in U-boats during WWII. He's already made some good progress:
http://www.subsim.com/radioroom/showthread.php?t=113591

Yes, I saw that thread on Monday and I'm really looking forward to his work. He did a great job on the American version. When there is bad weather or poor visibility I think the slide rule method using a collision course is still the best way to intercept since it's tough to do a range snapshot and you have to get really close to verify AOB.

[MudMarine]

I understand that the S-Class Boats in the campaign does not have a TDC. Is this correct?

If this is correct those tables will be very useful.