TDC Woes

[Cathy Howat]

What is the best way to plot an angle on bow for a mathematically challenged 60 yo noobie skipper?

[TorpX]

Ok, I'll try to give you a quick lesson on the TDC.

First, know that the AoB is just one part of the firing solution. To compute a proper firing solution, you need four things:

1. Aob - often estimated by 'eye'. Many in this game, use plotting with the map-contacts, to determine this on the nav-map.

2. Range - usually estimated by use of the stadimeter, or RADAR.

3. Speed - usually estimated by using the plot; distance moved divided by time. Rule of thumb: distance in yards moved in three minutes / 100 gives speed in knots (approximately). So, a target that moves 800 yards in 3 min. can be said to have a speed of 8 knots.

4. Bearing - this is self-evident from index ring on periscope or TBT.

If you are new to the game, or rusty, I would advise to use the map-contacts option. This will give you certain and precise locations to plot on your charts, and you can get a feel for the way the AOB compares to the view of the target you see. You should periodically pause the game, and study the dials and outputs of the TDC, so you can develop an understanding of the geometry involved.

Note that many different methods have been used to compute firing solutions, according to the inclinations of the players. If you don't use the map-contacts option, it is much harder to estimate AoB, and range, (and thus speed computations are likely to be off), so the whole business becomes very uncertain.



In the diagram below, the target ship is at T0, moving toward T1, and the sub is at U0 moving toward U1. The Aob is the angle measured from the target's bow to the bearing line of your sub. It can be port (left) or starboard (right). [Maybe you already knew this?]

As I said before, you can determine the Aob by measuring it off the plot, after you have marked several observations. This is probably the easiest way, if you are using map-contacts. In real-life, skippers usually estimated it by 'eye-balling', or with calculations involving the aspect ratio.

I won't say this, or any way is 'best', that might lead to arguments here, as everybody has their own favorite.

Note that the Aob is likely to change throughout the approach, even though the target is following the same course. This will sometimes lead to confusion.

[Cathy Howat]

Thanks for that

[Aktungbby]

Cathy Howat! http://en.wikipedia.org/wiki/Torpedo_Data_Computer

[Jimbuna]

Looks like your sorted Cathy, welcome to SubSim

[Cathy Howat]

Thanks for the help guys, fair winds and following seas

[fireftr18]

Welcome aboard Cathy!
Help will always be given to those who ask. Whether they deserve it or not.

The crew I have polishing the propellers seem to be having some trouble.
Go help them.

[TorpX]

Originally Posted by Cathy Howat

Thanks for the help guys, fair winds and following seas

Is any of this helping you?

Sometimes, we might assume too much, or too little prior knowledge. Feel free to ask follow-up questions.

HERE is a tutorial you can download about Aob.

HERE is a download program that has a 'training mode' that will generate random ship views, where you can try to estimate the Aob, and see how well you do. I've used this one, and consider it to be very useful in this regard. (You don't have to get caught up in the other mathematical features of the program.)

[Pisces]

Originally Posted by TorpX

...
In the diagram below, the target ship is at T0, moving toward T1,

I don't see it. Aside from the text all I saw was an empty quote window. You may want to check post #2.

[Cathy Howat]

Got myself a plastic protractor and ruler, now I work it ou on the screen for real

[TorpX]

Originally Posted by Pisces

I don't see it. Aside from the text all I saw was an empty quote window. You may want to check post #2.

Hmmm.......... it shows up for me.



In any case, Aktungbby's diagram is just as good. The Aob is marked as θ_Bow in that diagram.

[Pisces]

Originally Posted by TorpX

Hmmm.......... it shows up for me.



In any case, Aktungbby's diagram is just as good. The Aob is marked as θ_Bow in that diagram.

Nevermind, I'm using an ancient version of the Opera browser. Chrome works ok with it.