Lateral Speed Method

[Efshapo]

There are some similarities with the constant bearing method since my technique exploits the same mathematical constant which is lateral_speed = speed * sin(AOB), the gyro angle being directly related to lateral_speed.

In my opinion, the real new trick here is the use of the horizontal centiradians scale which is really faster than maneuvering the sub to get a constant bearing. This is what I haven't seen anywhere else, and would like to know if it had been documented before.

I understand one could do it using direct bearing change but I wonder if bearing measurement is as accurate as the horizontal scale...

[derstosstrupp]

Originally Posted by Efshapo

Yes, there are some similarities with the constant bearing method since my technique exploits the same mathematical constant which is lateral_speed = speed * sin(AOB), the gyro angle being directly related to lateral_speed.

In my opinion, the real new trick here is the use of the horizontal centiradians scale which is really faster than maneuvering the sub to get a constant bearing. This is what I haven't seen anywhere else, and would like to know if it had been documented before.

I’m not referring to the constant bearing method though. Auswanderungsverfahren, as I said, deals with bearing change. Like I said, the only difference between your method and the traditional method, is that you are measuring the bearing change In centiradians and not in degrees of bearing.

I’ve never seen it anywhere else done with centiradians, that part is new, but the overall method is as old as the 1920s when this was developed in between the wars.

Here’s an old video of me doing it with degrees:

[Efshapo]

From TVRE ( http://www.tvre.org/en/acquiring-torpedo-firing-data ):

The main disadvantage of the Ausdampfverfahren method was the relatively long time needed for suppressing changes of target bearing. That's why, on the basis of this method, another procedure was developed, the so called Auswanderungsverfahren method. This procedure was less accurate than Ausdampfverfahren, but required taking only two target bearings 1 minute apart and measuring (or estimating) the distance to the target during the taking of the first bearing.

Yes, thank you! That's indeed really close to what I'm doing.

Again, I guess bearing reading is probably not as accurate as horizontal scale reading but I'm glad someone gives me a document (or rather the name of a procedure) closely related to what I proposed!

We already had the 4- and 3-bearings method, I guess we could call this one the 2-bearings method.

Thanks again.

[derstosstrupp]

Of course, happy hunting!

[Efshapo]

I just noticed that you had actually already replied this same answer on my video. And I also already thought you were talking about the constant bearing method, I'm so sorry.

Thanks again for you obvious expertise!

[derstosstrupp]

Originally Posted by Efshapo

I just noticed that you had actually already replied this same answer on my video. And I also already thought you were talking about the constant bearing method, I'm so sorry.

Thanks again for you obvious expertise!

No worries at all! German is famous for loooionnnnngggg words and the words for these methods look similar at a glance.

[Efshapo]

BTW, there's another huge advantage in using the centiradians scale instead of turning the periscope, which is that you can use several chronos at the same time.

Of course, you can do it like I did in my video, measuring real and lateral speeds simultaneously. But you can also multi-check your measurements! I recently started to use one chronometer to measure lateral speed from -4 to +4 centirad, as in the video, but also from -5 to +3, and -3 to +5, which gives me 3 time values! I can then check that they are similar, and take the median one, or an average. I then do the same for real speed, using -1, 0 and +1 marks. It's a real gain in accuracy!