Correct AOB with OLC GUI

[Antiacus]

I'm probably being dense here, but isn't AOB just relative bearing from the target boat to yours?

So if I set up at say, 800 meters abeam of his course (to starboard) i can just set range to 800 and AOB to 90 right?

I'm not understanding the "subtract 180 if the target is moving away" bit.

Thanks.

[joegrundman]

If you are 90 degree abeam of him then yes that is AOB 90 because AOB is indeed the target's relative bearing to you.

However if the target is presenting an AOB of 90, it cannot be said to be moving away from you.

If the target is moving away from you, it will be showing you an AOB of between 91 and 180.

Becasue the AOB finder can only resolve AOB's of 5-90, if the target is moving away from you, then you should subtract the computed AOB from 180.

It's all perfectly logical

[Puster Bill]

Originally Posted by Antiacus

I'm probably being dense here, but isn't AOB just relative bearing from the target boat to yours?

So if I set up at say, 800 meters abeam of his course (to starboard) i can just set range to 800 and AOB to 90 right?

I'm not understanding the "subtract 180 if the target is moving away" bit.

Thanks.

If you are indeed on a perpendicular course to your target, you can set the AOB to 90 degrees (Port or starboard as appropriate) providing the periscope or UZO is at 0 degrees. Then when you move the periscope/UZO to the actual bearing of the target, the AOB will be correct.

You can also enter the range to his track at the same time, and the vorhaltrechner will give the correct range when you swing the periscope/UZO back on target.

In both cases, that of course assumes that neither you nor the target have changed course.

The reason for the "subtract 180 if target is moving away" is if you are using the Kriegsmarine whiz-wheel to find the AOB (I believe OLC has it. I use one I constructed), the outer scale only goes from just under 6 degrees to 90 degrees. If you get an answer of, say, AOB 70, but the target is moving *AWAY* from you, then you know the AOB is past 90 degrees. So, you have to subtract 70 from 180, giving an AOB of 120.

If it helps you to visualize it, an Angle On Bow of 120 degrees is equivalent to an Angle On Stern of 70 degrees.

Since the wheel doesn't know or care about the difference between AOB and AOS, you have to resolve that difference yourself.

The American SACF/IS-WAS wheel has markings that complete an entire circle (ie., it goes all the way up to 360 degrees), and so you can read an AOB greater than 90 degrees directly off of the wheel. The only problem with using that one is that it is marked in yards, not meters, and that using it without converting the meters that you will get for ranges into yards will cause you to overestimate speeds by a knot or two.

[Siara]

Originally Posted by Puster Bill

If it helps you to visualize it, an Angle On Bow of 120 degrees is equivalent to an Angle On Stern of 70 degrees.

Something is not all that clear here

[snwcrsh]

I always thought the best way to explain was with the flashlight: Imagine a guy standing on the bridge of the target vessel. He holds one flashlight directly in direction of the bow, i.e. the course his ship is heading. The other flashlight he points at your submarine.

The angle between those two beams of lights is the AoB.

If the ship is heading away from you (i.e. the AoB is greater than 90°), you from 180 subtract the AoB. (Effectively the guy with the flashlight would stand at the stern)

[Pisces]

Originally Posted by Puster Bill

The reason for the "subtract 180 if target is moving away" is if you are using the Kriegsmarine whiz-wheel to find the AOB (I believe OLC has it. I use one I constructed), the outer scale only goes from just under 6 degrees to 90 degrees. If you get an answer of, say, AOB 70, but the target is moving *AWAY* from you, then you know the AOB is past 90 degrees. So, you have to subtract 70 from 180, giving an AOB of 120.

If it helps you to visualize it, an Angle On Bow of 120 degrees is equivalent to an Angle On Stern of 70 degrees.

Make that "AOB of 110". But you're forgiven.

[Puster Bill]

Originally Posted by Pisces

Make that "AOB of 110". But you're forgiven.

Humbled. I did the math quick in my head.

I should have just looked at my SACF/IS-WAS.

D'oh!

Im my defense, though, I take more care in getting a good firing solution than I took in writing that post. I've gotten good enough that I can hit to 2K+ consistently, which poses other problems, like making sure the red pixel of a flag at the masthead of you target doesn't have a swastika in the middle of it! I *HATE* coming back after sinking a Dido and several freighters to learn that I received negative renown!

[GoldenRivet]

aob is the angular difference between three points... the target's course, the target and your position.

I think you are thinking of "intercept angle"... Intercept angle is the angle formed where your path intersects the target's path.

[onelifecrisis]

Antiacus, all clear? Or shall I show off my extra ordinary (that's two words on purpose) MS Paint skills?

[Antiacus]

I'm all clear! (and a little shamed)

Thanks so much for the excellent replies.

I was subtracting 180 from the solution rather than subtracting the solution from 180 essentially just trying to use the reciprocal and my head was a little fuzzy from 3am beer and tiredness.

Plus i'm a bit of a trigonomical dunce to begin with You guys, on the other hand, rock. What a fanstastic forum.