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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Relative bearings
From: Gary LaPook
Date: 2015 Apr 17, 17:33 +0000
The relative bearing to the target was displayed on the azimuth scale on the submarine's periscope so could be read out with great accuracy. The "angle on the bow" was an estimate, a "judgement," made by the submarine's skipper based on his observation of the aspect of the target ship. They were trained on silhouettes of the different types of enemy ships, head on, forward bow, broad on the beam, etc. so that he could  estimate the "angle on the bow" (actually the relative bearing on the target ship of the submarine's periscope, (hopefully  not seen)). This angle was used to calculate the course of the target ship and was used, along with the relative bearing and an estimate of the target's speed, to work out a "firing solution," the course to aim the torpedo in order for it to lead the target and cause a hit. The skill of the skipper in determining the "angle on the bow" was probably the most important thing in obtaining hits.This could be worked out by plotting or a vector diagram or, more accurately, by the "target data computer" a mechanical computer using cams and gears to do the computation.

gl

To: garylapook@pacbell.net
Sent: Thursday, April 16, 2015 11:01 AM
Subject: [NavList] Re: Relative bearings

```On 4/16/2015 12:36 AM, Paul Hirose wrote:
>
> Unless terminology has changed since WW2, "angle on the bow" doesn't
> mean relative bearing in submarines. Well, actually it does, but it's
> the relative bearing from target ship to sub, increasing port and
> starboard from the target's bow. For instance, port 90 angle on the bow
> means the sub is on the target's port beam, regardless of the relative
> bearing *to* the target.

Thank you Paul. I did indeed post, "Angle on the bow appears to be from
the observer's bow to the target, while target angle is from the
target's bow to the observer." I either misread or ran into one of
"those" sites, which like me, professed knowledge it did not possess.

After spending a goodly amount of time with the Wikipedia article and
illustrative photographs trying to reconcile the seemingly contradictory
results, it suddenly dawned on me that the "Angle on the bow is a
variation of target angle used by United States Navy submarines"
statement also referred to the *target* vessel, not the sub. After that
things fell into place.

http://en.wikipedia.org/wiki/Target_angle

> That meaning is also made clear by former fleet boat skipper Edward
> Beach in his classic war novel "Run Silent, Run Deep". If you've seen
> the movie you'll hardly recognize the book, which puts less focus on
> interpersonal drama and more on technical detail.

I have not seen the movie or read the book. I did however listen to a
radio play on a set the size of a dresser in rural Indiana circa 1957. I
recall the ending was distressing to a young boy.

There also seems to be a submarine computer simulation by the same name.
```

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