TDC

[Frederf]

I think I see the misunderstanding here and it's likely in part to my overly particular nature. I'm saying that ownship motion is not necessary to have a valid solution at the moment of firing. If, at the instant of firing, targetRange-AoB-targetSpeed are correct then the solution is correct.

The ownship motion only comes into play keeping a correct solution correct over time, which is replacing the previous solution with a newer solution. The ownship course and speed are not involved in the individual solutions themselves. I would like to highlight the distinction between a solution proper and an evolution of a solution. The former consists of a picture using (relative) target position & motion while the latter is an operation that needs (relative) motion of ownship as well as (relative) target position & motion to transform one picture into the next.

As for the German TDC, it's been a while since I've used it last so I had to remind myself. The only "update solution helper" that it has is a tie between the periscope bearing and the AOB setting which is something the American TDC doesn't do. So as periscope bearings are made the AOB updates to maintain the relative target couse using a very simple mathmatical relationship. The effect is that not only does changing ownship heading degrade the solution, so does any change in range. The German TDC (outside of constant range special cases) is a perfect example of a TDC that provides only instantaneous solutions.

I'm pretty confident that the German TDC doesn't have ownship speed and course information because such data only have 2 possible uses:
1. Continuous solution a la PK
2. Converting/duplicating all relative courses and bearings to their magnetic equivilent like the American TDC does with its inner/outer ring dials.

[Rockin Robbins]

In any event, the German TDC is just a really neat piece of machinery, and with a little ingenuity taking the place of American technology, I don't think it gives up much in the way of effectiveness.

I was showing another Subsim member how the Americans weren't the only ones who could take blind shots. Simply set up a Fast-90 and keep the blasted scope down. Fire when the sonar bearing is at the correct lead angle. Boom! A blind shot just like the high falutin' American prima donnas! Make sure the shot is set for the proper gyro angle beforehand! You want that gyro angle as small as possible to mitigate effects of sonar bearing error.

Of course, sonar bearing is not as accurate as a periscope bearing. You want to close the range as far as possible. But it's a darn sight better than popping up the scope, being seen and watching that CV do its imitation of a top fuel dragster and be at 30 knots in five seconds...

[Frederf]

Reading through those TDC manual pdfs I found out what the "target length" dial is for. The TDC allows for direct input of sound bearing (which is 0.5° accurate in the real thing at the proper filter frequency or better) and using the range, AOB, and half the target length, will correct the sound bearing into the equivalent visual bearing on center of target.

I'm curious about developing a quick and dirty method of converting sound bearing to visual bearing for sonar PK checking and even more accurate sonar targeting.

[Rockin Robbins]

The bearing conversion is done in-game. Our sonar bearing points to MOT.

Hey, did you see those inputs for distance between perisope and torpedo tubes? The inputs for torpedo speed? There are all kinds of fascinating things going on there with all sorts of interesting implications. For instance, they could have actually transplanted an American TDC into a little bitty U-Boat and made it work in pretty short order! Or used the same TDC in an S-Boat or Fleet Boat.

The TDC was built into two cases, side by side, so they could fit through the hatches and it could be installed without taking cutting torches to the hull.

But what really interests me are the photos of the difference and trigonometry modules. Yikes! They were doing with shafts and gears what we think takes a microprocessor. Those TDCs, German, Japanese and American, were art masterpieces as much as utilitarian machinery. Their designers were brilliant as any computer engineer of today.

[Frederf]

Originally Posted by Rockin Robbins

The bearing conversion is done in-game. Our sonar bearing points to MOT.

I haven't found this to be the case. I've had really, really good PK solutions that stick on the target like white on rice over several minutes and the sonarman on follow nearest contact is shouting bearing that are consistently 1-3degrees behind.