speed calculations.

[psykopatsak]

First off, hi all, i am new here, and this is my first thread. i started subsumming with SHIII a while back, then SH4, then i got bored of it, and went back to SHIII with GWX3.0. everythings great so far, except my best save was corrupted >:C

so i was wondering here, always when i've tried full realism, there is always one thing that never ever works unless im stationary - the speed calculation.

from what i understand, its based on the bearing changing in relatoin to range, but if my sub is moving too, the calculation gets screwed. 2 knots can become 11 knots, wich is unacceptable!:nope:

so i wonder to all you people who plays at 100%, help me tick the last box so i can rightfully earn my next 100K tons, mwahaha!:arrgh!:

[Freiwillige]

The TDC takes your speed into account. Although it loses accuracy the faster you go so keep it under 2 knots and your golden.

If at periscope depth 2 knots is good...no periscope wake to spot.

[Morts]

what i used to do when i played on 100% was i marked the ship when i spotted it, then i stalked the ship for up to 10 hrs, placing a marker on it every hour and measuring the distance. after the 10 hours passed i would measure the distance from the first mark to the last, i would then check a speed chart and see what speed would travel that distance in 10 hrs, only missed 1 shot doing it this way :yeah: and that was due to bad weather :arrgh!:

[psykopatsak]

well if the TDC takes my speed into account, how come that when i was travelling at six knots, the enemy went 11 knots, then i stopped to 0, and using the same range and AOB got me 2 knots...

[Snestorm]

The notepad method never worked for me.
Morts has a more foolproof method than I. That'll yield you a result as close to 100% accurate as possible.

I don't do any plotting. Generaly, I gather my information at long range, on the surface. It requires a-lot of time, heading changes, and eventualy speed variations. I do use The Watch Officer as knowing whether the range is increasing, decreasing, or constant throughout the proceedure is the key. On first sighting a contact, it can be helpful to dive and listen. Following him on the hydrophones can save a-lot of time, and risk of detection, while improving your intel on his general course. Then surface again and gather more intel.

The simplest, and more accurate, way is to follow him. (This is still not as accurate as Morts' method.)
The fastest way is to keep him at 090/270 tracking his range. When you think you're running paralel to his course work on matching his speed.

Once I get this information I decide on an attack plan.
F.eks. I'm attcking his starboard side, with my bow straight on.
UZO pointed at 000.
Next I go to the TDC.
Bearing: Should already read 000.
AOB: 90 Starboard.
Range: 1000 meters.
Speed: 7 knots.

Then I work my way in. In the final stage of the attack the UZO is pointed to where the Gyro Angle reads 000. When he gets there . . . . F I R E.

Warning: Don't use the Weapons Officer for anything as he will void out all your inputs.

Tak, Morts. Din måde er god.

[psykopatsak]

ok, ill do one of those if i have the time for it, otherwise i just take the speed and see if its messed up, and change it to what it looks like from experience...

[Hitman]

I do it like the real life Kaleuns did,

If I have the chance to stay surfaced and/or I detect the target from its side or stern, I steer paralell course and overtake him, getting his speed and course in the process by matching bearing and speed with the target

If I meet the enemy from a 45º AOB at most, I approach with dog leg curve and get the speed by using the fixed wire method

If I make a night surface attack or simply suddenly meet the enemy in any conditions, I estimate his speed by the bow wake and his course by eyeballing his AOB, and get close to make all possible errors count less.

[skookum]

If you happen to come across the contact while surfaced, take a visual range and bearing while he is still on the horizon. Plot the position on the map. Then wait three minutes and take another range and bearing Submerge right away. Plot the second position on the map. If you timed 3 minutes precisely between fixes then simply measure the distance in yards between the two fixes and divide by 100 to get the target's speed. Course is found simply by connecting the fixes with a line extending in the direction of travel.

[irish1958]

If you happen to come across the contact while surfaced, take a visual range and bearing while he is still on the horizon. Plot the position on the map. Then wait three minutes and take another range and bearing Submerge right away. Plot the second position on the map. If you timed 3 minutes precisely between fixes then simply measure the distance in yards between the two fixes and divide by 100 to get the target's speed. Course is found simply by connecting the fixes with a line extending in the direction of travel.
SH3 is in meters, and the interval should be 3m15s.
(39/36X3=3.25, or 3m15s)

[Platapus]

here are two good ways to get the speed of your target

If your target is approaching your submarine with an AOB of 20-160 use the first method. The closer to AOB 90 the better but we often have to take what we can get.

You must have identified your target ship and know its length in meters.

1. Point your sub just a few degrees ahead of your target

2. Point your periscope at 000. Do not lock the periscope view to the target. Periscope must remain motionless.

3. When bow of the target ship touches the periscope hairline start your stopwatch (I have a real stopwatch, I find it easier to use than the in-game one)

4. Do not move your periscope.

5. When the stern of your target touches the periscope hairline, stop your clock. Note time in seconds that it took for the target to pass "through" the periscope hairline.

6. Lower periscope. We are trying to be sneaky you know.

7 Use this formula

1.94 X (Length of target ship in meters) / (Seconds it took your target ship to pass through the periscope hairline) = Speed in knots

No need to determine range. No need to determine AOB (However the closer to 90 AOB the better. No need to compensate for the speed of your submarine (This is why you are headed straight toward your target)

If your target is approaching your submarine with a large AOB (80-90 degree AOB), there is another technique that is a bit harder to use but pretty useful. Presented with a deep bow of appreciation and gratitude to Hitman for his help in translation. :salute:

You must have identified your target ship and know the height of the mast in meters

1. Point your sub either directly toward (bearing 000) or directly away (Bearing 180) from the target ship.

2. Make note of the speed of your submarine and maintain this speed.

3. Lock the scope to the target and note how many marks on the vertical scale cover the target ship from the water line to the top of the mast. For example, the number of vertical marks from the water line to the mast of your target is 2 marks. With this method, it is more likely you would be using the low power setting on the scope.

4. Start your stopwatch.

5. When the target ship “Doubles” its height on the vertical scale (for example: started out covering 2 marks and now covers 4 marks), stop your clock and note the time in MINUTES.

6. Use this formula

(Mast height in meters) x 10 / (time it took the target to “double” in minutes) x 0.03 = relative speed in knots. But we are not done yet. Take this answer and

A. Subtract your own speed if you are approaching the target (bearing 000)

B. Add your own speed if you are headed away from the target (bearing 180)

Now you have the speed of your target. Note this method works IF the vertical scale is in 1/10 of a degree. If you use any mod that changes this scale, the formula will be inaccurate.

This second method works best if your target is approaching your sub with an AOB of 000. The further off from AOB 000 the more inaccurate, but remember that you can be off on the speed of your target and still get good hits.

Hitman did I get this right?

Hitman’s explanation is way more clear than mine. :salute:

http://www.subsim.com/radioroom/showthread.php?t=152372&highlight=mast+height+1%2F16


Good hunting!

[Snestorm]

I do it like the real life Kaleuns did,

If I have the chance to stay surfaced and/or I detect the target from its side or stern, I steer paralell course and overtake him, getting his speed and course in the process by matching bearing and speed with the target

If I meet the enemy from a 45º AOB at most, I approach with dog leg curve and get the speed by using the fixed wire method

If I make a night surface attack or simply suddenly meet the enemy in any conditions, I estimate his speed by the bow wake and his course by eyeballing his AOB, and get close to make all possible errors count less.

Hey Hitman, this is cool.
I finaly found somebody using the same methods as me.

I've got to ask it.
For a daylight submerged attack,
do you also prefer an opposite heading to the convoy/target,
with torpedoes being fired at 90 degrees?

I don't like traveling in the same direction as a convoy,
for fear of being run over by a merchant.

[Hitman]

Platapus, yes you got it right, but beware that this was elaborated for a reticle divided in mils -as the real ones were-, and not in degrees -as in SH3- so I can't assure that it will work unless I do the maths and check if the result is correct. :up:

For a daylight submerged attack,
do you also prefer an opposite heading to the convoy/target,
with torpedoes being fired at 90 degrees?

I don't like traveling in the same direction as a convoy,
for fear of being run over by a merchant.

Each option has advantages and disadvantages, as I see it:

Heading against the convoy:(Passiergefecht or Engagement en passant)

-You get in faster
-You get through the fore escort screen quicker because her speed and yours is added, and you can keep a more silent running

But:

-You need to turn 90º to make the proper zero Gyro angle shot, and for that you need a lot of space (Which you don't have between the columns)
For angled shots, you can only use properly the rear tube, because the bow ones will have the torpedo turn against the target motion, which increases chances of missing. From the UKH, paragraph 151: "The 90° angled attack should only be used for small convergences; i.e., when the torpedo, before turning, moves in the same direction as the target. It is very difficult to estimate the D.A. for large convergences, especially in attacking at short range. Consequently, the 90° angled shot with a small convergent displacement of the target is used: in running fights in the form of the bow torpedo attack; in engagements en passant in the form of the stern torpedo attack."


-You also need a good amount of seaman's eye to decide when to start turning, because the added speeds of you and the convoy also make them go by way faster.
-Once the attack has been carried out, the motion of the convoy will soon leave you outside it on the rear, where all escorts will find you easier

Heading with the convoy:(Running fight):

-You can do 45º/90º angled shots between columns and hit more vessels with your forward tubes (You need a good estimate of distance, though, to ensure correct convergence) while staying safely between the enemy ships

-You can use the convoy as cover after the attack, as you won't slip through the rear of it that quick. This will hinder a lot the escorts, as they have to maneuver between columns to get a position to track and depthcharge you, and in real life (not modelled in the game) they would have more fear of dropping their ashcans in order to avoid killing seamen swimming around from sunk ships. There is also a lot of noise inside the convoy, which hinders the enemy hydrophones (But not the ASDIC!)

But:

-You have to wait longer until the convoy reaches you, increasing chances of a zig-zag throwing you out of the projected convoy path

-You have to stay longer in the vicinity of the escort screen

Summing it up for real life (Not for SH3), the BDU clearly recommended running against the convoy as best option, see paragraph 106 of the UKH:

"As a matter of principle, every underwater attack should be so prepared and carried out that the launching of torpedoes can take place at the earliest possible moment. Favorable opportunities of attack may be lost by hesitating. If conditions allow, the submarine should therefore go to meet the enemy. It is wrong to keep ahead of the enemy and wait until he comes into range."

[PL_Cmd_Jacek]

2. Point your periscope at 000. Do not lock the periscope view to the target. Periscope must remain motionless.

3. When bow of the target ship touches the periscope hairline start your stopwatch (I have a real stopwatch, I find it easier to use than the in-game one)

4. Do not move your periscope.

5. When the stern of your target touches the periscope hairline, stop your clock. Note time in seconds that it took for the target to pass "through" the periscope hairline.


I use this excelent technique. It's very usefull. Moreover you can use modification of it.

1) if you are stopped, you are not obliged to direct your bow toward the target.

2) You do not need the calculator, if you just use "2" instead of "1,94", it is enough

3) If you are stopped, you can get target's speed quicker. Just lock the target (mostly it will be the middle of the ship), then unlock and immediately start the clock. When stern match the periscope line - stop the clock. Now just devide lenght of the ship by seconds and you will received target's speed.

[Platapus]

3) If you are stopped, you can get target's speed quicker. Just lock the target (mostly it will be the middle of the ship), then unlock and immediately start the clock. When stern match the periscope line - stop the clock. Now just devide lenght of the ship by seconds and you will received target's speed.


Wow, I never thought about that. Especially when the speed can be off a bit and you can still hit. :yeah:

[Snestorm]

Thanks Hitman.
I generaly keep going straight in, without turning.
I guess that's why I can only target 1 ship, and have to use 3 torpedoes.
Even then, it's not a sure thing by any means.

The running attack is an attractive option from just outside,
but I'm afraid of it inside the convoy.

[psykopatsak]

i usually goes straight for inside the convoy, short distance, lots of targets, and few escorts.