Simple question plus pro navigation quesiton in here

Cool, this thread exploded a bit because it's an interesting subject. Intercepting is our bread an butter. For now, I'm using the "Intercept Theorem" from the French forum and practiced with that to see my options. I want an intercept persé, but I draw a line parallel to the enemy's route at 1200m distance, so I have time to set up the perfect angle. My plan is to practice that first, because you have to draw fast and accurate. the enemy ship is moving you know

Then, I'll move on the next methods here. Eventually I anticipate that none or 100%, but all of them combined will provide great insight. Practice is the key I noticed.

Two (three) things are needed to take into account: the moving ships and your sub operates at different speeds. It catches up and gets in advance on the surface for speed. But then it needs to go down, so your intercept-planning must take a slow moving sub into account for the next 5 km as well.

I'm only at mission 5 now (excluding the erprobungsstelle in SH3Commander), but I'm learning.

Edit: maybe I take a break and evaluate YellowFin's formula's first. I'm drawn to it like a seeking torpedo or something

Originally Posted by Sailor Steve

One option is to use SH3 Commander, which lets you assign yourself your own locations.

I play with this since the beginning (lol few days ago). How do I assign coordinates to patrol? I don't want to leave the 2nd yet.

[bstanko6]

But if you plan the attack at night you don't have to dive.

This is why I don't use the heavy math. As long as you know the target speed, and direction, you can plot when and where to attack. You can stalk your target until dusk with enough information.

Ugh I need a stopwatch in the nav room badly. Is it easy to port the existing stopwatch in periscope room to the nav room?

Originally Posted by bstanko6

But if you plan the attack at night you don't have to dive.

This is why I don't use the heavy math. As long as you know the target speed, and direction, you can plot when and where to attack. You can stalk your target until dusk with enough information.

Yeah, I most likely won't use the math either. But for the learning phase I think it's good to explore this subject, also from the mathematical perspective. I'm sure it will add greatly to the phenomena of "insight".

[YellowFin]

Obviously the interception course should not be used to basically collide with your target. The idea is to get into the general vicinity of the interception point.

Usually I do the calculation with a lower speed than I'm actually going to sail at or I adjust the course after calculation slightly s.t. I arrive earlier, i.e. I increase/decrease the angle s.t. my track gets shorter while I sail at the speed used in the calculation. This way I arrive on scene early and I can acquire the target either through spotting or hydrophone.

One of the two main methods of obtaining an attacking position described in the U.Kdt.Hdb [1] (an original tactical manual for Submarine Commanders published by the German Kriegsmarine) can roughly be summarized as follows:

1. acquire a visual or acoustic bearing of the target (by intercepting it)
2. move away or closer to target s.t. you can keep track of target without being detected. I try to keep the target at the horizon and almost completely faded out.
3. overtake target while taking frequent bearings in regular intervalls (every 5-10 min, and write down the time of the first bearing for the speed calculation later) and plotting them on the map. You don't need the distance to target at this point all though it doesn't hurt to keep an eye on it, in case the target changes course or speed
4. once sufficiently ahead of target (I usually got about 11 km in good visibility) turn in to cross its bow, while still taking bearings and plotting them
5. slow down as you approach 0° AOB, use recognintion manual to identify 0° AOB and plot this relative bearing on map. It will cross all the previous bearings you've taken and it represents the exact heading of the target. Knowing the length of the intervals and the time of the first bearing you can calculate a very good estimate of target's speed
6. dive and go on a course exactly opposite to the target's heading about 1.5 km off of target's track, at ahead 1/3
7. keep taking bearings to have an informed estimate of distance to target
8. Since you are on a course parallel to the target, relative bearing of target = AOB, verify using recognition manual
9. once the target is 2-4 km away turn in (for bow shot) or away (for stern shot) at 90°, slow ahead after executing turn

Check out my play through here, where I demonstrate all the methods I have described.

Happy hunting

[1] A (partly inaccurate/confusing) translation of the original U.Kdt.Hdb.

Did you manage to plot an interception course with the tutorials ?

Originally Posted by Kendras

Did you manage to plot an interception course with the tutorials ?

I even made a screeny during the planning phase but I accidentally left the time compression on so I couldn't make a second to show the near perfect result! I used the "Intercept method" from the French forum! I'll post screeny of planning phase any sec. I'm totally excited.

Edit: added screeny planning
http://i.imgur.com/zX70S8M.png

The main thing I didn't account for is that when my ship was at 4.5 Km from the victim, I submerged, so my speed slowed down a lot. I need to find the visual geometric trick to compensate for that. I'll make it my standard to dive at 5Km distance from enemy. Secondly... I need to adjust for the time I need to get to periscope depth from, say, 30 meter depth.

Edit 2: Right now hasing that guy and trying again. This time I try to compensate for the both the items I mentioned above (slow speed due to submerging and loss of time due to going back to periscope depth at slowest speed). I'll try with a threshold of 1000 meter (was 200m, total of 2000 meters distance from interception point).

Good job !

Near perfection, almost creepy. I was a bit too harsh on self-criticism in my screenshot. Next practice: YellowFin's math. I'm almost jumping from excitement!
(Notice that I assumed my speed as follows because I slow down due to diving: ((real_speed + 8knots)/2 ) * 1.1

http://i.imgur.com/VsjS1h9.png

Also, I notice the stopwatch-method (3m:15s of recording) puts the automatic periscope speed estimation to shame. Learning as you go.

Originally Posted by YellowFin

<snip advice>

Check out my play through here, where I demonstrate all the methods I have described.

Happy hunting

I am now as I type this. Just a quick note: I see you have no Anti Aliasing as well. I just fixed mine. You're not interested in that? Cheers.

[YellowFin]

Originally Posted by Machariel

I am now as I type this. Just a quick note: I see you have no Anti Aliasing as well. I just fixed mine. You're not interested in that? Cheers.

Hey, thanks for your comment! Nice YT avatar btw

Is the aliasing the ugly fine lines that are shown as dashed lines, like the antennas and such? Yes, I'm very interested in fixing that.

[YellowFin]

Originally Posted by Machariel

Near perfection, almost creepy. I was a bit too harsh on self-criticism in my screenshot. Next practice: YellowFin's math. I'm almost jumping from excitement!
(Notice that I assumed my speed as follows because I slow down due to diving: ((real_speed + 8knots)/2 ) * 1.1

http://i.imgur.com/VsjS1h9.png

Also, I notice the stopwatch-method (3m:15s of recording) puts the automatic periscope speed estimation to shame. Learning as you go.

The forumla beta = asin(v_g/v_e * sin(alpha)) will not work with that correction, it assumes true persistent speeds (at the time of the calculation) until interception. Or are you calculating an average with your correction?

I take from your posts that you look for an approach course when you are already in visual range of the target. I use the intercept course formula for intercepting a map contact from a B-Dienst message, e.g. when a convoy pops up at the other end of the grid square, or a grid square over from where I am patrolling. That means they're usually dozens if not hundreds of kilometers away. With the intercept course I get into a range of about 5-10 km from the target's supposed track and then the tedious work of determining its exact speed and heading begins (combined with getting into an attacking position).

My method:

1. Get map contact from B-Dienst or friendly u-boat
2. intercept using formula until about 5-10 km from supposed track
3. check horizon, usually I have the target abeam, either slightly ahead (if I used the calculation tel quel), or behind if I made sure to arrive early
4. if no visual of target can be obtained -> dive and try to get acoustic signal
5. If you are way too early hunt up supposed track surfaced with intermittent dives if visibility is bad until target is found. To decide whether you're behind or in front of target, check time of map contact, the correctness of your calculations and whether or not the target might have turned.
6. once found, overtake by 5-10 km, turn in to get 0° AOB and obtain exact heading
7. move off track by ~1.5 km and approach slowly on an opposite but parallel course
8. turn in for shot at 90° AOB

If you want to go for the perfect, well prepared 90° angle shot I recommend you overtake your target by ~10 km. You can go down to ~5 km at night or in bad visibility.

Tactical advice from the U.Kdt.Hdb. :

(I'm paraphrasing)

Stay surfaced for as long as possible without risking detection. Speed and maneuverability are much better on the surface. The submerged movement is for the surprise attack only.

I still sometimes make the mistake of diving immediately after taking 0° AOB bearing. The smart thing to do is to speed up again (I usually slow down to make sure I don't miss exact 0° AOB) and take a position 1.5 km off track and turn for opposite but parallel course and then dive, because all this maneuvering while submerged takes a lot more time

In German engineering language we differentiate between dive-boats and submarines (ger. Untersee-), and according to this definition only types XXI and onward count as true submarines. Our U-boats (Type II, VII, IX) are meant to dive only for the actual attack and for evasion. They stay surfaced for most of the time.

I hope these tips are helpful. Have a nice weekend everyone!

[Sailor Steve]

Originally Posted by Machariel

I play with this since the beginning (lol few days ago). How do I assign coordinates to patrol? I don't want to leave the 2nd yet.

When you first open Commander there is a blank slot at the bottom left. Put the cursor on it and it says "Leave blank for SH3 generated patrol grid." Type the grid you want into that slot.

Originally Posted by YellowFin

Hey, thanks for your comment! Nice YT avatar btw

Is the aliasing the ugly fine lines that are shown as dashed lines, like the antennas and such? Yes, I'm very interested in fixing that.

I have only the day before yesterday solved mine. Here's the thread: http://www.subsim.com/radioroom/showthread.php?t=230507

Originally Posted by YellowFin

<snip tactics>

For the first question, yes I use a guesstimated average taking submerged speeds into account. The formula is only to develop insight. Eventually the graphical interception method using Thale's theorem can be done on a whim. So everything becomes relative after practice and experience.

I have practiced with the B-radio map contact through bstanko's YT channel. I can find the target if it's not too far away. But the hydrophone is too in-accurate I noticed compared to visual acquisition for approach angle. But I'll check this comment again and see if I overlooked something.

Originally Posted by Sailor Steve

When you first open Commander there is a blank slot at the bottom left. Put the cursor on it and it says "Leave blank for SH3 generated patrol grid." Type the grid you want into that slot.

Yes, I've found it. It wasn't blank, it revealed where my next assignment would be.