Target speed calculation made easy

[lms_oid]

Hi mates,

I received my deluxe version yesterday and tried it for 3 hours (with 1.1 patch installed) : it's very nice IMO! Then I came to this forum and discovered that many simers were complaining about the speed calculation broken in the TDC... Even if it is a bug as it is written to work in the manual, I believe that it is fairly more realistic that way. I were always asking myself in SHIII who was the guy in my uboat who was calculating the speed estimation while I was pushing "the little button on the chronometer"... So now in SH4 with manual TDC on, we can use the chronometer but the guy who was calculating like crazy in SHIII is gone. Not a big deal IMO. We will just have to work our trigonometry again ;) .

There are several ways to do estimation of speed but I would like to present you the way I use. It's limited because it's only exact at an AOB of 90° and with the sub travelling slow. However, it is a very good estimation between 75° and 105° AOB. The interest of this method is that you do not need a calculator which would kill the immersion and that it is fast (no map drawing). You just need a "target speed estimation Table" that you can find below.

I find it to be immersive and far more realistic than the always accurate magic speed that you obtain in SHIII...

Hope it will helps some simers.

http://img115.imageshack.us/img115/3977/sh4tableoc2.jpg

lms_oid

Edited : Table modified - 30 seconds for range from 1750 to 2000 yards.

[ijozic]

I find it to be immersive and far more realistic than the always accurate magic speed that you obtain in SHIII...
This is debatable depending on what is your impression of what are the tasks that you as a captain must do. I hope they fix this issue with chronometer for people who want to keep it simpler.

But this table is quite useful regardless, thanks.

[P_Funk]

It would be cool if you could make a few tables for different common AOBs. Like one for 45 and like 25 or something. You could have a few charts. Hell you could just give us the equation involved in that chart and we could all make our own custom ones.

Me personally I'd make one for every say 10 or 15 degrees. Probably need fewer too as you get closer to 90.

[nattydread]

I'd think map plotting would be easier. Take a range and bearing of the target, start clock and mark it on the map. Wait a minute and repeat. Use the ruler to measure the distance travelled. Now you have time and distance, calculating speed is easy after that...granted it requires we have bearing info as a map plotting tool. I have yet to play the game so thats something im not sure we have. But if it is, its accurate under all conditions.

[RedHammer]

I missed the Nagato battleship I was aiming at and instead hit a carrier far behind.

Sorry, It seems that none of us newbies can elaborate exactly how much we need the Auto Speed Determination of the chronometre to even get started using a manual tdc. Because the issue is this simple: We cannot hit anything of what we are aiming at. As in, nothing, maybe by luck, if I crazily enough manage to determine the speed, by a wild guess, then maybe I hit once or twice.

Right now, It would be easier for me to put everything on Zero on the TDC, and just aim ahead of the enemy ship I`m shooting at, and simply develop a feel for how many clicks in the periscope, ahead, of the enemy ship, I have to shoot, to get a hit.
But for real.. Who had time and resources enough to practice that.. that person would not be a sub captain for long..


S! to all


SK

[lms_oid]

This is debatable depending on what is your impression of what are the tasks that you as a captain must do. I hope they fix this issue with chronometer for people who want to keep it simpler.

Don't get me wrong, I totally understand that people want this bug to be solved. I just find that it's very realistic as this and I love it.

I'd think map plotting would be easier. Take a range and bearing of the target, start clock and mark it on the map. Wait a minute and repeat. Use the ruler to measure the distance travelled. Now you have time and distance, calculating speed is easy after that...granted it requires we have bearing info as a map plotting tool. I have yet to play the game so thats something im not sure we have. But if it is, its accurate under all conditions.

Yes, this way is good too. You only have to multiply the distance travelled in one minute by 60 to have the actual speed. Depending on the speed you may have to wait a little longer though. By waiting 3 minutes between the two checks, you only have to multiply by 20... And it is a lot of fun to draw that on the map (very immersive IMO).

It would be cool if you could make a few tables for different common AOBs. Like one for 45 and like 25 or something. You could have a few charts. Hell you could just give us the equation involved in that chart and we could all make our own custom ones.

Me personally I'd make one for every say 10 or 15 degrees. Probably need fewer too as you get closer to 90.

The formula I use is only true at an AOB of 90 because it use trigonometry. The exact formula is :

1 yard = 3 feet
1 nm = 6080 feet
1 hour = 3600 seconds

BC = Bearing Change in degrees
S = Speed in knots
R = Range in yards (given by the stadimeter)
T = Time between the to bearing checks in seconds

S = (tan BC x 3 x R x 3600)/(T x 6080)

However, the more your AOB is far from 90° (more or less), the more the speed is underestimated by this table so you can guess that adding x knots to the estimated speed would be a good idea.

lms_oid

[P_Funk]

After thinking it through and recalling all the old ways of getting target info in SH3, I still dig the functionality of the nomograph.

In SH3 if I needed speed I could take the range, mark it on the map, run the stopwatch for any period of time (longer the better) and then apply those numbers to the nomograph and get a solid speed out of it. And it works at any AOB.

If the stadimeter in SH4 is better than the one in SH3 then range shouldn't be an issue. That means that all you need is time, and thats a number that you can generate yourself.:up:

But I dig the charts anyway. I want to work out a chart system that can spare me the need of a nomograph under as many circumstances as I can avoid.

[OS1Mac]

Thanks for the table! :up:

[Ragtag]

After thinking it through and recalling all the old ways of getting target info in SH3, I still dig the functionality of the nomograph.

In SH3 if I needed speed I could take the range, mark it on the map, run the stopwatch for any period of time (longer the better) and then apply those numbers to the nomograph and get a solid speed out of it. And it works at any AOB.

If the stadimeter in SH4 is better than the one in SH3 then range shouldn't be an issue. That means that all you need is time, and thats a number that you can generate yourself.:up:

But I dig the charts anyway. I want to work out a chart system that can spare me the need of a nomograph under as many circumstances as I can avoid.

Nomograph?? what the heck is that? :P (yes, i'm green but wanna learn) ;)

[Corsair]

Why would the good old 3min 15sec method not work in US subs ?

[Shigawire]

I want the nomograph in SH4 asap. Is there any way to get it in?

Loved it in SH3..

This is Wazoo's nomograph mod for SH3

http://i4.photobucket.com/albums/y136/wazooda/findknots.jpg


The 3 lines at the bottom is the nomograph. If you know any 2 values of the 3, you can discover the 3rd unknown value. If you know time travelled, and distance travelled, you can find speed. If you know speed and time travelled, you can find distance. All you need to do is make a line between the 2 known points, and the line will cross the 3rd line where you will find the value you were looking for.
Quite ingenious.

[lms_oid]

Why would the good old 3min 15sec method not work in US subs ?

Imperial metrics? However, if you have more than one minute, drawing the all thing on map should be the better way. The table I made is more intended for fast solution building when you have to fire quickly.

lms_oid

[Corsair]

Why would the good old 3min 15sec method not work in US subs ?
Imperial metrics? However, if you have more than one minute, drawing the all thing on map should be the better way. The table I made is more intended for fast solution building when you have to fire quickly.

lms_oid

Right ! but then if now distances on the map are in nautical miles like it should be, it makes things even easier as you don't need the nm/km conversion anymore... Distance travelled in 3mns x 20 = speed in knots.

[lms_oid]

Right ! but then if now distances on the map are in nautical miles like it should be, it makes things even easier as you don't need the nm/km conversion anymore... Distance travelled in 3mns x 20 = speed in knots.

Exactly what I said :D !

By waiting 3 minutes between the two checks, you only have to multiply by 20...

lms_oid

[RedHammer]

i try again and again but the numbers are just way off. Cant hit anything.

S!

RH

[lms_oid]

i try again and again but the numbers are just way off. Cant hit anything.

Try the third mission of the naval school. You should find a speed of 9 knots for your target. In order to find this result you must :

- Identify the ship in the recognition manual and validate in order to send the mast high which should be aroud 75 to the Stadimeter.
- If this is correctly done, you should find a range of about 1000 yards with the stadimeter. Validate this info to send it to the TDC.
- Set the angle of bow to 90° on the right (which is approximately the case) and send again the info to the TDC by validating.
- Check the bearing and launch the chronometer for 10 seconds. You should note a bearing change of about 3° during those 5 seconds.
- By using the table I provided, you can see that the speed of the target for 1000 yards / 3° should be 9 knots. Set the target speed to 9 knots and validate to send the info to the TDC.
- Congratulations : You have entered a valid solution in the TDC!
- Launch the tropedo and it WILL hit!

Remark 1 : By playing this mission with manual TDC disable, you can see that the speed of the target IS 9 knots, so if you find 9 knots manually, you are right!

Remark 2 : Don't forget to VALIDATE (by clicking on the button) each info you gather or you enter in order to send it to the Stadimeter or the TDC. If you don't do that, the TDC won't be updated with information you've gathered and the torpedo will go everywhere but not on your target.

lms_oid

[Von Hinten]

First of all a thanks to lms_oid for this lovelt table. I'm sure that it'll come in handy and I will definitely try this out. :up:

The 3 lines at the bottom is the nomograph. If you know any 2 values of the 3, you can discover the 3rd unknown value. If you know time traveled, and distance traveled, you can find speed. If you know speed and time traveled, you can find distance. All you need to do is make a line between the 2 known points, and the line will cross the 3rd line where you will find the value you were looking for.
Quite ingenious.
Would you believe that I've looked and looked and looked again at those lines and never knew what they were there for? :doh: I feel so silly at some times. :nope:

Much to learn, this young one has ... hmm? :yep:

[RedHammer]

i try again and again but the numbers are just way off. Cant hit anything.
Try the third mission of the naval school. You should find a speed of 9 knots for your target. In order to find this result you must :

- Identify the ship in the recognition manual and validate in order to send the mast high which should be aroud 75 to the Stadimeter.
- If this is correctly done, you should find a range of about 1000 yards with the stadimeter. Validate this info to send it to the TDC.
- Set the angle of bow to 90° on the right (which is approximately the case) and send again the info to the TDC by validating.
- Check the bearing and launch the chronometer for 10 seconds. You should note a bearing change of about 3° during those 5 seconds.
- By using the table I provided, you can see that the speed of the target for 1000 yards / 3° should be 9 knots. Set the target speed to 9 knots and validate to send the info to the TDC.
- Congratulations : You have entered a valid solution in the TDC!
- Launch the tropedo and it WILL hit!

Remark 1 : By playing this mission with manual TDC disable, you can see that the speed of the target IS 9 knots, so if you find 9 knots manually, you are right!

Remark 2 : Don't forget to VALIDATE (by clicking on the button) each info you gather or you enter in order to send it to the Stadimeter or the TDC. If you don't do that, the TDC won't be updated with information you've gathered and the torpedo will go everywhere but not on your target.

lms_oid
I cant get any bearing change on the position follower unless i input a speed value in the tdc. Besides there are no numbers, only small little lines. So I cant even count it accurate. Sorry for the trouble, and thank you for answering so quick earlier, I guess I am just getting frustrated by this issue, having to spend 2 days to learn other methods of getting somewhat accurate speed and aob into the tdc is a pretty steep learning curve, and sure does cause alot of stress.

S!

RH

[lms_oid]

I cant get any bearing change on the position follower unless i input a speed value in the tdc. Besides there are no numbers, only small little lines. So I cant even count it accurate. Sorry for the trouble, and thank you for answering so quick earlier, I guess I am just getting frustrated by this issue, having to spend 2 days to learn other methods of getting somewhat accurate speed and aob into the tdc is a pretty steep learning curve, and sure does cause alot of stress.

Don't be frustrated, everybody has to learn and I don't know many games where you have this kind of work to do (IMO, SH manual TDC is really realistic).
If 10 seconds is to short, you can still use the formula I gave earlier with T=30 seconds or more. But by zooming (mouse wheel) and by locking the target using 'L', you should be able to estimate the bearing change for 10 seconds.

lms_oid

[RedHammer]

rgr. I think I found a way to determine bearing,
First I find the mogami in the recognition manual, input it to the tdc.
then I went to the map, and drawed a line from the Mogami`s stern to maybe 100 meters in front of it. Then I took the Compass, and clicked in 30 yards away from the end of the "100 yard" line, which the Mogami will reach within x amount of time, and i expanded it, and then made it so it pointed against my sub. Then I took the protractor at the exact end of the 100 yard line and to the 30 yard away from end. and then to my sub, I had a value of about 63 degrees to his Starboard. Which is then, AOB, then I hurried up and got range and speed into the TDC.

I repeated the above AoB trick I just did, and thus, I managed to calculate AoB within 30 seconds. Which was about 3 degrees in 30 seconds, give or take.

Finally! All 4 torpedoes hits at exact same place on the Cruiser, and he goes down quick!


Thanks alot for the solution :D

S!

RH

[RedHammer]

uhm nevermind, that method i just mentioned didnt work, i got too much of a bearing change for the speed to be correct..

So what you are saying, is that I have to check the bearing change by Visual Eyesight? How will I be able to see, with my own eyes, thru a periscope, at 1100 yards, if he changes his course by 3 degrees?

Getting frustrated again.. Ubi.. please fix the auto bearing finder..


S!

RH

[tedhealy]

Thank you much for the table :up:

[Nightmare]

I'm wanting to use the plot over time, so I'm making my drawings on the nav map. What's the formula to figure out speed using this method? I'm also using imperial mesurments.

[lms_oid]

I'm wanting to use the plot over time, so I'm making my drawings on the nav map. What's the formula to figure out speed using this method? I'm also using imperial mesurments.

Say you have plotted a move of 0.6 nm in 3 minutes. You now know your target is making 0.6 nm each 3 minutes. Since there is 20 times 3 minutes in an hour, your target speed is (0.6 x 20) knots (since 1 knots = 1 nm per hour). So your target speed is 12 knots.

lms_oid

[Barkhorn1x]

Thanks for this - I took your table - and the methodolgy comments and made a nice reference sheet out of them.

[lms_oid]

uhm nevermind, that method i just mentioned didnt work, i got too much of a bearing change for the speed to be correct..

So what you are saying, is that I have to check the bearing change by Visual Eyesight? How will I be able to see, with my own eyes, thru a periscope, at 1100 yards, if he changes his course by 3 degrees?

Getting frustrated again.. Ubi.. please fix the auto bearing finder..


S!

RH

I know what you did wrong and in fact I was doing it wrong to!

The time you spend entering the AOB and estimating the speed, the bearing changes! And the bearing is only updated in the TDC by the synchronisation button on the stadimeter (first tool of the 3)! Just before launching the torp with AOB and speed set, you should go to the stadimeter and send another time the infos to the TDC or the bearing information in the TDC will be false and you will fire behind the target!

http://img251.imageshack.us/img251/8763/sh4tdcdh4.jpg

On the video below, you can see that just after entering speed, I launch the first torpedo without re-updating the bearing in the TDC. And just after that I launch a second torpedo with bearing updated. The two torpedoes take very different route and the first one miss but not the second one!

http://www.youtube.com/watch?v=-puNWizWWlo

lms_oid

EDIT :

Reading again your last post :

How will I be able to see, with my own eyes, thru a periscope, at 1100 yards, if he changes his course by 3 degrees?

I realize that you don't know what is the bearing I talk about! There is no link at all with the course of the target! It's the number you can read at the top of the screen when using the periscope. You should be able to read that!

[Rykaird]

Say you have plotted a move of 0.6 nm in 3 minutes. You now know your target is making 0.6 nm each 3 minutes. Since there is 20 times 3 minutes in an hour, your target speed is (0.6 x 20) knots (since 1 knots = 1 nm per hour). So your target speed is 12 knots.

lms_oid

Thanks very much for this simple explanation of how the equivalent to the old 3:14 rule works!

[Nightmare]

Say you have plotted a move of 0.6 nm in 3 minutes. You now know your target is making 0.6 nm each 3 minutes. Since there is 20 times 3 minutes in an hour, your target speed is (0.6 x 20) knots (since 1 knots = 1 nm per hour). So your target speed is 12 knots.
Thanks you! This should help tonight when I practice a little more. I was using Neal's method of using roughly half the targets max speed with some minor tweaking.

Another thing I found is there is a button in the lower right corner of the position keeper (just to the right of the position keeper/torpedo settings switch). Once you take your range, AOB, and speed and enter them into the TDC, hitting that button will set the TDC to track. In theory, if you are accurate with those three things, the TDC will keep an accurate firing solution and update the torpedo gyro angles continually.

When I'm ready to fire I:
1) raise the scope
2) check if the generated bearing in the TDC matches (or close to it) the bearing from the scope.
3) check to see if the generated AOB in the TDC matches roughly with what I see in the scope.
4) take one last range and submit to TDC and see if the generated range was off.
5) If all those things check out, it's time to shoot!

[micky1up]

why not have the sonar report the rev count of the engine and have a TPK (tuns per knot) for each vessel ie a battle ship has a tpk of 8 and the rev count is 80 therefor the speed equals 10 kts

[lms_oid]

why not have the sonar report the rev count of the engine and have a TPK (tuns per knot) for each vessel ie a battle ship has a tpk of 8 and the rev count is 80 therefor the speed equals 10 kts

A very good way indeed, well known by SC or DW players! I didn't tried that in SH4 (only 3 hours of play and I'm leaving tonight for one week skiing holidays), is it working? Can you ask the sonar to do that? It would be great!

lms_oid

[ccruner13]

i think neal did that in the video he made? he went to the sonar station and went through his contacts and found his target...i didnt know what he was doing but my guess would be that. so now where are the listings of ships tpk?

http://www.youtube.com/watch?v=7EoyadhXrVI

[Rykaird]

I know what you did wrong and in fact I was doing it wrong to!

The time you spend entering the AOB and estimating the speed, the bearing changes! And the bearing is only updated in the TDC by the synchronisation button on the stadimeter (first tool of the 3)! Just before launching the torp with AOB and speed set, you should go to the stadimeter and send another time the infos to the TDC or the bearing information in the TDC will be false and you will fire behind the target!

On the video below, you can see that just after entering speed, I launch the first torpedo without re-updating the bearing in the TDC. And just after that I launch a second torpedo with bearing updated. The two torpedoes take very different route and the first one miss but not the second one!

http://www.youtube.com/watch?v=-puNWizWWlo

lms_oid


Can you do me a favor and post the setting you are using in torp school? I always hit aft, in the same spot back by the airplanes.

I'm updating all my info in the instant before I fire:

AoB 70 starboard (as measured on the nav map)
Speed 9 knots
Distance 1010 yards (from the stadimeter)

I'm firing at approx bearing of 348 (giving me near zero gyro angle). Bow cap is open, torp set to fast.

The only way I can hit him dead center is to set the speed to 11 knots, which is faster than what I'm measuring.

Thanks!

[RedHammer]

I will try as good as I can to explain again: The AOB does NOT update, UNLESS, I have a speed input. And even so, that speed input MUST be the ships actual speed. So I am back at start.

I`ve tryed many methods here but none of them seems to be working for me. If they work for others, great :D I have no choice but letting my future pleasures of sh4 into the hands of the devs. They gotta fix the Auto Speed determinator in the Chronometer. Or I can`t simply play this game.


S!

SK

[W_clear]

:up: :up: :up: :up: :up: Thank you much for the table

[joea]

why not have the sonar report the rev count of the engine and have a TPK (tuns per knot) for each vessel ie a battle ship has a tpk of 8 and the rev count is 80 therefor the speed equals 10 kts
A very good way indeed, well known by SC or DW players! I didn't tried that in SH4 (only 3 hours of play and I'm leaving tonight for one week skiing holidays), is it working? Can you ask the sonar to do that? It would be great!

lms_oid

That did not work in WWII though??

[micky1up]

why not have the sonar report the rev count of the engine and have a TPK (tuns per knot) for each vessel ie a battle ship has a tpk of 8 and the rev count is 80 therefor the speed equals 10 kts
A very good way indeed, well known by SC or DW players! I didn't tried that in SH4 (only 3 hours of play and I'm leaving tonight for one week skiing holidays), is it working? Can you ask the sonar to do that? It would be great!

lms_oid

That did not work in WWII though??


sonar operators have always been able to count the revolutions on the contacts they hear all we need is the TPK value of the unit its not simulated in the game but i think it wouldnt be hard to add to the game

[RTKSpiff]

Nice table :)

To get the effect of AOB just divide your answer by sin(AOB), but then
you need a calculator :stare:

[Viktorbg]

Im using this V=L/T * 1.96
V=L/t*3600s"1hour"/1850m"1knot"
V=Speed
L=Ship lenght
T=Time of 1 ship lenght


with speeds below 4-2 the observation time is too much(~90 s) and above 35 knots the error tolerance is droping but the AOB dosen't mater at all.

I can't found warships lenghts anywhare, plz help

srr for my english

[Shadowmind]

If you want a general purpose equation for calculating speed you can use the following:

speed(knots) = (Di * sin(theta) * 3600)/(sin(AOB) * Tm)

where Di is the distance in nautical miles or
Di = Dy * 0.000493738

where Dy is the final distance to the target in yards

Theta is defined as the change in bearing during the measurement time

AOB is the Angle on the Bow.

Tm is measurement time in seconds.
I did all of this in Excel and use it on my PocketPC. Now I know this is "authentic", but they did have sine tables in WWII. So I could look this up on tables.....

So for an example to compare this equation with the chart, take a ship that is 1500 yards away and had a bearing rate change of 3 degress over 10 seconds and is 90 AOB:
speed = ((1500 * 0.000493738) * sin(3 deg * pi / 180) * 3600) / (sin(90 * pi/180) * 10 sec)
speed = 13.95 knots


Now take an example of a ship that is 1000 yards away, with an AOB of 25 deg, it has moved 2 degrees in 10 seconds:
speed = ((1000 * 0.000493738) * sin(2 deg * pi / 180) * 3600) / (sin(35* pi/180) * 10 sec)
speed = 10.82 knots

It works well. I have a bunch of hand drawn figures, but I am too lazy to scan them in and post them. I hope the text description is useful.

[akdavis]

I know what you did wrong and in fact I was doing it wrong to!

The time you spend entering the AOB and estimating the speed, the bearing changes! And the bearing is only updated in the TDC by the synchronisation button on the stadimeter (first tool of the 3)! Just before launching the torp with AOB and speed set, you should go to the stadimeter and send another time the infos to the TDC or the bearing information in the TDC will be false and you will fire behind the target!

On the video below, you can see that just after entering speed, I launch the first torpedo without re-updating the bearing in the TDC. And just after that I launch a second torpedo with bearing updated. The two torpedoes take very different route and the first one miss but not the second one!

http://www.youtube.com/watch?v=-puNWizWWlo

lms_oid


Can you do me a favor and post the setting you are using in torp school? I always hit aft, in the same spot back by the airplanes.

I'm updating all my info in the instant before I fire:

AoB 70 starboard (as measured on the nav map)
Speed 9 knots
Distance 1010 yards (from the stadimeter)

I'm firing at approx bearing of 348 (giving me near zero gyro angle). Bow cap is open, torp set to fast.

The only way I can hit him dead center is to set the speed to 11 knots, which is faster than what I'm measuring.

Thanks!

Mk. 14 torpedos are bugged at the high speed setting. The are not travelling as fast as the TDC thinks they are. Use low speed setting on your torpedos and see how you do.

[raduz]

i think neal did that in the video he made? he went to the sonar station and went through his contacts and found his target...i didnt know what he was doing but my guess would be that. so now where are the listings of ships tpk?

http://www.youtube.com/watch?v=7EoyadhXrVI

no, he wasnt doing THAT. he just identified targets for sonarman. there is no listing of ships tpk because the dev team did not simulate the propeller pitch.

[Gaspode]

This is my first post, so hello everybody.

If you want a general purpose equation for calculating speed you can use the following:

speed(knots) = (Di * sin(theta) * 3600)/(sin(AOB) * Tm)


Yes, you're right, that's an accurate formula to calculate the relative motion of a target.
This looks like it can't be simplified, but we can use some nice properties of sin to get an approximation for
small thetas. Since sin is 0, sin' is 1 if theta = 0 and sin is concave in the interval between 0° and 90°,
we can simply replace sin(x) by x in a small area around 0.
If theta is smaller than 30 degrees, the error factor x/sin(x) is always smaller than 1.05, so we overestimate the
real relative movement by no more than 5 percent. The only problem here is that x is theta in radians, so we must do
some ugly conversion with theta since we have theta in degrees. Now lets have a look at the formula:

speed[kts] = (3*3600/6080)[s/yd * kts] * range[yd] * pi/180 * theta[deg] / time[s] * (1/sin(aob[deg]))

Since 3*3600/6080 * pi/180 equals 0.031002559, we can simply replace this ugly factor by 0.03 resulting in

speed[kts] = (3*/100)[s/yd * kts] * range[yd] * theta[deg] / time[s] * (1/sin(aob[deg])).

Again we make a small error, this time always underestimating the target speed by about 3 percent.
Well, that's a lot easier, but we still can't calculate sin(aob) without a calculator or sin table.
So let's look at some values (aob rounded to nearest integer):
aob 1/sin(aob)
90° 1
72° 1.05
65° 1.1
60° 1.15
56° 1.2
53° 1.25
50° 1.3
46° 1.4
42° 1.5
30° 2
20° 3
15° 4
12° 5
1/sin(aob) is symmetrical to 90°, so if the aob is lets say 108°, 1/sin(aob) is 1.05.
From this table we can conclude that any aob below 50 degrees produces very inaccurate values, since we most likely
don't know the exact aob and have guessed it. At these low aobs only a few degrees change the factor by 10 or more percent.
We also see that we get really good approximations when the aob is between 70 and 110 degrees.

So to get the real relative speed of a target you can use this procedure:
1. get range to target
2. get bearing and wait t = range/100 seconds
3. after waiting t seconds get 2. bearing
4. estimate aob
5. compute theta (2.bearing - 1.bearing, ignore minus sign)
6. look up value of 1/sin(aob) of the nearest aob in the above table, use next higher entry if theta < 15
7. multiply theta by 3
8. multiply the result by 1/sin(aob)
and you have computed the target's speed

Note:
If the target is moving too slowly, you can of course wait 2*t or 3*t etc. seconds, but then you have to divide by that
factor afterwards. Waiting 3*t seconds looks promising since the 1/3 cancels out the 3 in step 5. But watch out, theta
should not become much larger than 30 degrees. Another danger is waiting a too small time, resulting in a too small theta.
If theta is too small, you have to be really precise. For example, an error of 0.5 degrees means 10% when theta = 5°,
and in that game it's hard to find out exact bearings.

This also works if you are not using imperial measures. If your range is in meters, simply add 10% to the final speed.
(The true conversion factor is 1/0.9144=1.0936, but 1.1/0.9144 = 1.00584, so 1.1 is very exact)


Now a few questions remain: 1. It's an approximation, how accurate is it?
Due to the fixed under- and variable overestimation, this method produces values that lie within 5% of the true speed
if theta is in the interval between 0 and 40 degrees. Of course, this error estimation is only valid when your
measurements are accurate...
The ideal theta range is from 20 to 30 degrees where over- and underestimations nearly cancel out each other, resulting
in an error of under 1%.
But of course the 1/sin(aob) estimation using the table produces an additional small error, this time over- or underestimating the speed
by up to 2.5% if your aob estimation was perfect.
So if theta is smaller than 15° always use the higher of the two possible 1/sin(aob) values if the aob lies between two table entries,
or use the next higher value if the aob is in the table or very close to any of these values. This way, the underestimation of about 3%
in that interval is replaced by a small overestimation of less than 2%. And we know now, that all speed estimations are either nearly
exact (±2%) or small overestimations of up to 5% (only if theta > 30, which we want to avoid anyway).
Of course, since this is only an approximation of the target's speed, you should always fire a spread unless your target is very close
(say under 1000yd) or moving so slowly, that the error of up to 5% can be ignored.
An error of 5% means 1kts when your target is moving at 20kts, which sounds much when you want to fire at long range targets.
But actually it isn't. If your target and your torpedos travel at 30kts, and the torpedo has to travel 3000m to reach the interception point,
then your target will also travel 3000m, and 5% error means 150m. But most of the times your target will be much slower than the torpedo, and
the error will be less than one ship length if you fire at targets in a reasonable range.
So if you fire a spread you can cancel out that error. If theta was greater than 30°, you're overestimating too much and should aim at the stern
or slightly behind the target if it is far away. Otherwise aim at the mid of the target.
I've tried this method several times in a quick mission in SH3/GWX and my 4 torpedos fired as a 5° spread arrived always 100 to 300 meters
behind a destroyer moving at about 25kts 2.5km away from me, whose speed I estimated with theta = 5.5° and an aob of around 70° as 20 kts.
I wanted to know what was wrong, and did it again with autoaiming. And, what a surprise, my estimated aob was always way too high. The real aob was
around 50°, so I have used 1.05 for 1/sin(aob) instead of the right value 1.3, resulting in an error of about 20%.
But the error induced by the aob estimation isn't so important when engaging slow targets at small ranges.
In the SH3/GWX torpedo exercise mission I engaged 2 targets at speeds of 8 and 7 kts and ranges of 1500 and 1000 meters. The first, a small
freighter, with 1 torpedo at an aob of about 80° which hit about 20 meters behind the mid, at which I had aimed. The other was a tanker which
I engaged at an aob of 120° with a 4 fish 5° spread, of which 2 hit and 2 passed behind, one only by a few meters.

2. Relative movement? So how much does my own movement affect the measured speed?
Well, your movement subtracted from the true target movement is the relative movement, when you have all movements as vectors.
So if you are moving in the same direction as the target, you have to add your speed to the calculated target speed (in case the bearing moves
towards your stern, multiply the calculated speed by -1 before adding your speed). If you are moving in the opposite direction, subtract your
speed from the calculated value. In cases where these vectors form a isosceles triangle, typically with your small speed between the two long
target speeds, your speed doesn't influence the relative speed. So you should try to move nearly perpendicular to the target's course, but
slightly in the same direction as the target. The course difference should be 60° if you expect it to be as fast as you are, and over 80° if
it is 4 times as fast or even faster.
Of course there is an exact formula to calculate the exact speed under all conditions, but it is too complicated to explain now,
this post is already long enough... ;) I will post something about it later.
For the moment just stay as slow as possible while estimating speed.
Well, that was much. And it sounds really complicated.
But it isn't, what we can easily see at an example:
(the following measurements have been made in the SH3/GWX mission "operation cerberus" using autoaiming)
The first sighting of the lead destroyer was at 3600m, bearing 340°. The target speed is 25kts.
3600/100 = 36, so we have to wait t = 36 seconds.

After 36s the target is at 345°, aob 46°.
theta = 345°-340° = 5°
1/sin(aob) = 1.4, since theta < 15 use 1.5
theta*3 = 15
15*1.5 = 22.5
since range was in meters, multiply by 1.1: 22.5 * 1.1 = 24.75
so we have computed a target speed of 24.75 kts, 1% lower than the true target speed

Lets wait another 36 seconds, so we have waited a total of 2*t = 72 seconds
Bearing is now 351.5°, aob 53°.
theta = 11.5°
1/sin(aob) = 1.25, theta < 15, use 1.3
11.5 * 3 = 34.5
34.5 * 1.3 = 44.85
meters, 44.85 * 1.1 = 49.335
since we waited 2*t, divide by 2: 49.335 / 2 = 24.6675
so we have computed 24.6675 kts, less than 2% too low

And now a third estimation after 3*36 = 108 seconds
Bearing = 0°, aob = 61°
theta = 20°
1/sin(aob) = 1.15 (this time theta > 15, so we don't increase it)
20 * 3: skip it, canceled out by / 3
20 * 1.15 = 23
23 * 1.1 = 25.3
so the computed speed is 25.3 kts, an overestimation of about 1%

And it is indeed very simple. Depending on the aob and the resulting 1/sin(aob) value, you can do these multiplications in a few seconds
in your head, or on a sheet of paper.
The numbers sometimes become very ugly, but you can round them to the nearest quarter knot or so to simplify the multiplications.
It is impossible to enter the speed more precisely, anyway.

Of course these estimations are not so exact if you misjudge the aob by 10° or so. The error may easily reach 10% or more, and you will miss targets
that are far away or very fast, as my example above shows (the first from question 1, it's the same target as in the last example).
So if you are very good at estimating aob, you can precisely estimate the target's speed.
If you tend to estimate the aob right, but sometimes over- and sometimes underestimate it by 10° or so,
you can also compute the speed after t, 2*t and 3*t seconds and then calculate the average of these 3 speeds to even out aob estimation errors.
But if you are not that good, like I am, you can still use this estimation when you want to shoot from the hip at a target of opportunity,
especially when the range is under 1000m and the aob is nearly 90°, then the formula is simply the
rule of thumb: theta*3. (or even simpler: theta, if you waited 3*t seconds. maybe +10% if the target isn't perfectly aligned.)

[BlackSpot]

*Gulp*:o

[Grotius]

As to sonar, my experience is that it doesn't work at all until you're just below periscope depth. Is that a feature or a bug?

[Sledge_57]

....<SNIP>........................Yes, you're right, that's an accurate formula to calculate the relative motion of a target..................<SNIP>................................ if you waited 3*t seconds. maybe +10% if the target isn't perfectly aligned.)

I have a headache now.................

Where's my Halo disc.......................:arrgh!:

[scooches]

So...quick question here as I don't have Sh4 yet. The Range tools in this sim measure distance like .8nm vice giving it in yards?! The Navy deals in yards for most everything except air control.

When we would mark contacts on the ship, it always referenced yards, 080 12,000 yards etc...this also worked well with the 3 minute rule. To give inaccurate distance measuring like nm w/ decimals is a bit absurd. It's one thing about SH3 that I didn't particularly care for either. Works well on a large scale chart, but when your talking closer in ranges, specific yards/meters would pay great dividends.

[WernerSobe]

in Real subs there was no magic involved. They used a tool that looked like a logarythmic ruler to find the speed. And it was fearly easy and quickly to use.

Another method was to guess the speed by counting the turns of screws. This only worked with ships they had turncharts for.

[greekfire]

Now take an example of a ship that is 1000 yards away, with an AOB of 25 deg, it has moved 2 degrees in 10 seconds:
speed = ((1000 * 0.000493738) * sin(2 deg * pi / 180) * 3600) / (sin(35* pi/180) * 10 sec)
speed = 10.82 knots

I assume you accidently entered 35 degrees into the formula for AOB. In the example, you quoted 25 degree AOB. Or did I miss something?

thnx!

[CableRouter]

why not have the sonar report the rev count of the engine and have a TPK (tuns per knot) for each vessel ie a battle ship has a tpk of 8 and the rev count is 80 therefor the speed equals 10 kts The max possible rev count in the game appears to be 47. So if you have a freighter with 8 turns per knot, you get the same rev count if the ship is moving 6 knots or 16 knots. SHIII was exactly the same.

[NefariousKoel]

So...quick question here as I don't have Sh4 yet. The Range tools in this sim measure distance like .8nm vice giving it in yards?! The Navy deals in yards for most everything except air control.

When we would mark contacts on the ship, it always referenced yards, 080 12,000 yards etc...this also worked well with the 3 minute rule. To give inaccurate distance measuring like nm w/ decimals is a bit absurd. It's one thing about SH3 that I didn't particularly care for either. Works well on a large scale chart, but when your talking closer in ranges, specific yards/meters would pay great dividends.
Yes, it only measures by a tenth of a nautical mile.

I can get by with it as-is using the 3 minute rule. You just have to extend the ruler a bit back and forth to see exactly how far into 0.5nm it is (for instance). If it just gets into 0.5nm but not close to the halfway mark, I know the target is doing 9 knots. I also let the stopwatch run until 6 minutes and mark again, though my speed estimation is perfect every time at 3 minutes using this methodology. The 6 minutes is for a better target heading more than anything.:arrgh!:

[greekfire]

Hey guys,

I'm brand new but I wanted to run this formula by everyone to see if it is sound mathematics regarding finding target speed.

I use the law of cosines. a^2 = b^2 + c^2 - 2bc(cosA)

....where a, b, c are triangle sides, with Angles A, B, C. I am solving for side 'a' which is the distance traveled over 60 seconds.

It supposed to be good for when you have 2 lengths and one angle of irregular triangle.

Here are my steps...
1. Identify target and determine initial range to target
2. Start timer for 60 sec while noting initial range and initial bearing
3. After 60 seconds, mark final range and final bearing
4. Determine Angle A by subtracting final bearing from initial bearing
5. Solve for 'a' by using above formula
6. Divide answer by 60 to get speed in knots.

Example:

Destroyer is traveling at approximately 90 degrees AOB at range of 1226 with bearing 335 degrees. After 60 seconds, the range of target is still 1226 but bearing has changed to 347 degrees.

a^2 = 1226^2 + 1226^2 - 2(1226)(1226)cos[347-335]
a = 685.12 (distance traveled over 60 seconds)
speed = 685.12/60 = 11.42 knots

* just figured this out so still not sure how it performs with AOB's that deviate from 90 degrees but seems to work well in game so far.

I have heard about guys using nav map to lay all this out but the ruler is terribly inaccurate using tenths of nm's so I'm at a loss for that approach. If anyone knows how to use map to determine target speed please pass that info on. It would be much appreciated. cheers.

[captainFlunky]

Hey guys,

I'm brand new but I wanted to run this formula by everyone to see if it is sound mathematics regarding finding target speed.

I use the law of cosines. a^2 = b^2 + c^2 - 2bc(cosA)

....where a, b, c are triangle sides, with Angles A, B, C. I am solving for side 'a' which is the distance traveled over 60 seconds.

It supposed to be good for when you have 2 lengths and one angle of irregular triangle.

Here are my steps...
1. Identify target and determine initial range to target
2. Start timer for 60 sec while noting initial range and initial bearing
3. After 60 seconds, mark final range and final bearing
4. Determine Angle A by subtracting final bearing from initial bearing
5. Solve for 'a' by using above formula
6. Divide answer by 60 to get speed in knots.

Example:

Destroyer is traveling at approximately 90 degrees AOB at range of 1226 with bearing 335 degrees. After 60 seconds, the range of target is still 1226 but bearing has changed to 347 degrees.

a^2 = 1226^2 + 1226^2 - 2(1226)(1226)cos[347-335]
a = 685.12 (distance traveled over 60 seconds)
speed = 685.12/60 = 11.42 knots

* just figured this out so still not sure how it performs with AOB's that deviate from 90 degrees but seems to work well in game so far.

I really wish I wouldn't have napped through every math class I ever had at this point.

[Tobus]

Great chart, I was on the verge of shelfing the game until patch 1.4b;) .
Now tonight I will give it a go once more.

[MudMarine]

CaptFlunky and Others,
Ye Gads! Flunky ya not only one who slept through math.:damn: My favorite sim in the past was Silent Service II. The days of those simple sims are over. :cry: What we need is a Sub Sim School on line! :hmm: Guess I got to bone up on my math ,YuK! Heck ! :cry: I got problems just doin my Taxes! :damn: I will have to study this thread a lot and practice , practice and practice till it becomes second nature.

I have some other questions abour SH4 but those are for another thread.

[Powerthighs]

uhm nevermind, that method i just mentioned didnt work, i got too much of a bearing change for the speed to be correct..

So what you are saying, is that I have to check the bearing change by Visual Eyesight? How will I be able to see, with my own eyes, thru a periscope, at 1100 yards, if he changes his course by 3 degrees?

Getting frustrated again.. Ubi.. please fix the auto bearing finder..


S!

RH


RedHerring, not sure if anyone ever answered your question.

The change in bearing doesn't mean how the course of the target ship changes. It means the change in direction you look to see the target.

This is easily measured through the periscope. Let's say you see a ship moving left to right across your periscope view, 2000 yards away. You place your periscope centered on the middle of the ship. You see the periscope bearing is 270, (i.e. the target is directly to your left).

You wait 30 seconds, then move the periscope to re-center on the ship. Now the periscope bearing reads 275.

That means the bearing changed 5 degrees in 30 seconds on a target 2000 yards away. Looking at the chart, that gives you a speed of 10 knots.

[Puster Bill]

Nice table :)

To get the effect of AOB just divide your answer by sin(AOB), but then
you need a calculator :stare:

Heresy! Use one of these:

http://img172.imageshack.us/img172/9828/p148pickettn200estrigun3.jpg

[Puster Bill]

Here is the thread where I explain how to use a slide rule to get AOB and speed given two range/bearing marks:

http://www.subsim.com/radioroom/showthread.php?t=112765&highlight=slide+rule

[NEOCortex]

I figured I'd join this forum and contribute alittle of my own efforts in determining a targets speed and AOB. I've made an excel file which does all my calculations for me.

http://files.filefront.com//;7546056;/

It may help to have some experience with excel to use this, but probably not necessary.

Instructions on this spreadsheet:
Cells in blue are where you input your information, cells in red show the most critical results.
In game, when you want to gather data on a target, set your subs speed and direction, then input your subs speed into the spread sheet.
As quick as possible, get a range/bearing to the target AND start the timer. This will be the range and bearing at time 0 seconds in the spreadsheet.
Keep recording range and bearing data at various times. When you are satisfied or just want results, enter all these readings into the spreadsheet. Extend the formulas in the 6 columns to the right to cover all the entries you just made (if necessary).
Note: DO NOT extend the formulas further then the entered data (w/ the exception of the AOB column), as this will create cells with nonsense values, and these values will screwup the final calculations.

This spreadsheet will take the readings you input and calculate an average speed and heading for the target.
If this is done correctly, then the spreadsheet will calculate the AOB for the all the bearings you took data at, as well as any future bearings you wish to look at.
It will also give you the heading of the target relative to your sub and the targets speed.

Final notes:
These calculations will only work if you use the right units, i.e. meters and seconds.
If you change direction or speed while you're doing this, start over!
If it looks like the target changed direction or speed during this process, start over!
The "averaging" was done by a linear fit of the data provided. See graph in spreadsheet to understand what is going on.
Positive AOB angles imply starboard and negative AOB angles imply port.
The positive x direction was defined as the forward direction of your sub and the positive y direction is defined as right 90 degrees of your sub.

[Gaspode]

Nice work, NEOCortex.

I made a program a few months ago which does nearly the same.
The only thing missing is the calculation of the relative data of the target. But you don't need a huge spreadsheet program to use it, and you don't have to copy the formulas for every contact. Plus you can track as many targets as you want and you can enter imperial or metric ranges :)

TDC (http://files.filefront.com/7292133) (couldn't resist naming it Target Data Calculator ;))

[OlegM]

Mk. 14 torpedos are bugged at the high speed setting. The are not travelling as fast as the TDC thinks they are. Use low speed setting on your torpedos and see how you do.

None of you torpedo gurus commented further on this, is this true? TDC overestimates Mk14 speed on high setting? :-?

[Hitman]

None of you torpedo gurus commented further on this, is this true? TDC overestimates Mk14 speed on high setting? :-?

We didn't think it was necessary as that was fixed in the 1.2 patch long ago:roll:

[OlegM]

None of you torpedo gurus commented further on this, is this true? TDC overestimates Mk14 speed on high setting? :-?

We didn't think it was necessary as that was fixed in the 1.2 patch long ago:roll:

Ah OK thanks. I do still get weird results with manual targeting sometimes - I don't know if it's due to me being an idiot, some game mechanics that I do not understand, a bug, or historic faulty gyroscopic guidance on torpedos (simulated by the game).

[NefariousKoel]

Mr. Mastruko-
The gyros have a little bit of play in the Mk14s in-game. I believe the depth keeping has a small variable to it also. Not to mention the extremely small chance that one will circle around back at you.


Also, if you're using the Imperial system, a couple things are still calculated in Metric such as the Stadimeter and torpedo depth. This is the biggest problem maker for me.

[RedHammer]

Hi all



After the new release of the SH4 Addon Uboat Missions. I believe I am experiencing what I hope to be just a nightmare in my sleep: Target speed again rendered useless...

and even if it did work.. its not like normal sh4 after it was fixed.. anybody got a clue on how to get it working?

Sincerely Yours

RHhttp://www.2and2.net/files/47c837b85ca22.jpg

[Rockin Robbins]

I'm afraid you're not in Kansas any more.:doh:

[Wilcke]

...that screen shot looks vaguely familiar.....

[DevilThorn]

It does not work like it did in sh3. But it works just like in the american subs. Get two range calculations and then hit the get speed button.

[LukeFF]

It does not work like it did in sh3. But it works just like in the american subs. Get two range calculations and then hit the get speed button.

And then you have to enter in the AOB.

[RedHammer]

Yeah I figured it out, the settings of the TDC was different, so that`s why I messed up, one look in my SHIII manual cleared it all up for me :)

Thanks! :D


Sincerely Yours

RH

[commandosolo2009]

could you be kind enough to make one for the metric system. And please explain what is bearing change.

[Pisces]

could you be kind enough to make one for the metric system. And please explain what is bearing change.Yards are about 1/10th shorter than a meter. So take the metric distance in meters and add 10% to find the line in the table.

A bearing change is the difference in the viewing direction through the periscope (or TBT, hydrophone sensor, etc.) of 2 moments you point it at the target.

Imagine standing alongside a road with a car approaching from your left. As it comes closer, the direction to it(=bearing) slowly starts to drift to one side of you. Once it passes you, the direction moves at it's quickest. (Be careful not to strain you neck ;) ) As it has passed you, the changing of the view direction slows down again until it is at the horizon. The table assumes you measure this view-direction change while he is passing the moment when the AOB is 90 degrees.

[yubba]

1ft/sec = 0.592kt works for me.

[Daniel Prates]

Yards are about 1/10th shorter than a meter. So take the metric distance in meters and add 10% to find the line in the table.

Interesting issue since few people in this forum are used to metric system. I just happen to live in a country were metric system applies to everything, so it's feet and miles and knots that makes things weird. But you get used to it.

So what's a yard? It is legally defined as beint exactely 0.9144 metre. That is the weird translation to it, since it is so much uneven. But it is also legally defined as being 3 FEET, or 36 INCHES. So it is a unit that belongs to the anglo-american system.

[Platapus]

Perhaps one of these decades the US will go metric.

If it were not for the drug trade, our kids would never learn the metric system. :D

[Rockin Robbins]

The sizes of metric measurements just don't fit the world, people or the things in it very well. When designing environments for humans, using measurements derived from basic human characteristics is appropriate. That is why the metric system will never be adopted in the US.

However, for dimensions having nothing to do with human beings, astronomical measurements, microscopic measurements, atomic physical properties, etc, there is some justification for using the metric system. In any event there is no decent excuse for any one not having a decent understanding of the metric system.

That doesn't mean that measuring my height in centimeters or weight in kilograms or the size of a room in meters isn't utterly ridiculous. Dimensions for tools and environments for use by man should be based on measurements and proportions of man. Base 10 is inappropriate, as physical properties are based on multiples of small prime numbers. Hence the common 12 units, 6 units, three units and other non decimal ratios in the English measurement system. You thought they were arbitrary? Think again. They are natural.

I know! Let's decree that the ratio between the diameter and circumference of a circle must be 10 for ease of calculation! Since when is ease of calculation justification for the destruction of natural truth?

[Daniel Prates]

I know! Let's decree that the ratio between the diameter and circumference of a circle must be 10 for ease of calculation! Since when is ease of calculation justification for the destruction of natural truth?

You clearly feel very strongly about this, eh?

I think that anything we're used to, will do just fine. Being from a metric-country myself, I can tell you that since we all grow up knowing it, it seems very natural and intuitive - and that the anglo-american system seems very unnatural and basically weird. The problem with "natural truth" is that nowadays it is impraticable to have mearurements based on the size of the arm of some long-ago dead king or something.

Now, it is obvios that some things can't be tampered with. Did you know that the french, during the early ears of the revolution, decided to convert the HOURS OF THE DAY to a metric-sort-of system? There would be 10 hours in the day or something like that. I think that they went a bit too far on that.

[TorpX]

Let's decree that the ratio between the diameter and circumference of a circle must be 10 for ease of calculation!

:03: RR makes a good point.

In many cases, one system is as good as another. I learned the metric system in school and liked it at the time, but don't see any advantage to it now. There are many physical constants which do not fit well in any system. Like the acceleration of gravity, g, or the speed of light, c, or Avagodro's number, etc. Civilization does not collapse because there are 24 hours in a day, months are not equally long, or there are 365.25 days in a year. (One of the things I like about the English system, for example, is that in physics, a foot-pound is easier to visualize than a Joule.)

BTW, I always thought it curious that the KM used metric-meters and English knots. Can anyone explain this?

[Daniel Prates]

BTW, I always thought it curious that the KM used metric-meters and English knots. Can anyone explain this?

Up until WW2, germany used metric values for everything, but I suppose "knots" was mantained for naval purposes since it was so traditional. It's not the same for instance in aviation, where airplanes would use kilometeres for both range and altitude, and km/h for speed.

Russia used this same system up until the fall of comunism.

[Rockin Robbins]

The use of knots exposes the Achilles Heel of the metric system. The numbers don't mean anything. They are all in the wrong ratios to each other to conveniently describe the relationships of natural objects, which perversely cling to proportions like 1/3 or 1/5, how many sides on a snowflake? Bet it isn't ten.

But the knot is a great unit because it has a relationship to a degree of longitude anywhere or a degree of latitude at the equator. There are 60 nautical miles to a degree. It is no coincidence that there are 60 minutes in a degree as well, is it? This has connections with our measurement of time, distance and angles. Now toss a metric measurement in there and all those obvious relationships just get entirely covered up in nonsensical decimal places of numbers in the power of 10. Nice even, obvious proportions hidden by the use of inappropriate units.

For instance, let's pick on the famous three minute rule we use in targeting. The number of hundred yards traversed by the target in three minutes is its speed in knots. Why? Because we have chosen to define the units to all have even relationships as shown above! The units make sense.

Of course we can do the same thing with the metric system in meters, we just have to pick the units to show the result, so we end up with the number of hundred meters traversed in three minutes and fifteen seconds is the speed in knots. Why the odd number, 3:15? Because the units have no relationship to each other. We've concealed a very important relationship between distance, time and angles. How many people have had to ask the question "Why 3:15?" They can't see the relationship. Inappropriate units hinder understanding of reality.

Even the Germans had the sense to use knots. There's a message there. (I'll bet the French aren't smart enough to use knots. They're the prime sponsors of the metric system.)

As much as anything else, the metric system is a proclamation of the political system of Revolutionary France in the first decade of the 19th century. Yes, they tried to make 10 hours per day, 10 days per week and have a metric year redefining the month and wiping out the relationships between lunar and solar movement in telling time. After all, man's stupidity is the measure of the universe. Be damned with real relationships, ease of calculation will be king even if the resulting numbers no longer calculate anything.:D

From now on all families are required to have ten children. Triangles must have ten sides.

You know I did find just one just about perfect decimal relationship. When a mixture of gas and air ignites in the engine of your car it expands almost exactly 1000 times. All together now: Metric System! This is too much fun! I hope I'm being entertaining as well as thought provoking. This kind of contention should be fun.

Actually the gist of my argument in favor of the appropriateness of the English system of measurements with all its charmingly archaic units is that they, like the natural world, tend to be proportioned by the ratios of small prime numbers or the products of small prime numbers, 1, 2, 3, 4, 6, 8, 12. Isn't it interesting that the number 5 rarely occurs? 1/5 is also a rare relationship in the natural world. Of course these relationships weren't chosen purposely in the way we think of selection. They came from simple observation of the proportions primarily of the human body. Of course the proportions of the human body are echoed in the rest of creation as well, but they had no way of knowing that. They just did what worked. There's an honesty to that. And a potential tragedy if in the name of ease of calculation we obliterate the wisdom contained in those units.

[TorpX]

One of the things I like about the english system is the degree-minute-second measure. One can devide 360 into 2,3,4,5,6,8,9,10,12,15,18,20,24,30,36,40,45,60,72, 90,120,180 parts (did I miss any?). Of course one can use decimal degrees or minutes instead.

I remember in trig, radians were used a lot, but outside of this I don't see too much use for them. I wonder what a carpender would say if you asked him to build a staircase with a slope of pi/4 radians? :O:

[Dogfish40]

I missed the Nagato battleship I was aiming at and instead hit a carrier far behind.

Sorry, It seems that none of us newbies can elaborate exactly how much we need the Auto Speed Determination of the chronometre to even get started using a manual tdc. Because the issue is this simple: We cannot hit anything of what we are aiming at. As in, nothing, maybe by luck, if I crazily enough manage to determine the speed, by a wild guess, then maybe I hit once or twice.

Right now, It would be easier for me to put everything on Zero on the TDC, and just aim ahead of the enemy ship I`m shooting at, and simply develop a feel for how many clicks in the periscope, ahead, of the enemy ship, I have to shoot, to get a hit.
But for real.. Who had time and resources enough to practice that.. that person would not be a sub captain for long..


S! to all


SK

Ahoy RedHammer
After reading and rereading some of the the patrol reports of the Fleet boats from the war, You are not far off in your feelings on the matter. In the early part of the war especially, the skippers were frustrated by the very same thing (Apart from the fact that the fish were faulty). I have read too many instances to count of perfect setups at 1000 yrds, 90 degree or comparable AOB, firing 4 fish and ALL MISS!. This is with all the personal assisting the Skipper! Most all torpedos fired at enemy ships in the first year of the war were misses. I've noticed in the game that ship's are taking evasive manuvers as soon as the fish reaches some visable distance, particularly in daylight and it doesn't take the ship much to adjust it's course and have the fish miss. So when you take your calculation, best fire a spread if you attacking during the day.
Point is, don't be frustrated. This is what the Fleet boats in WW2 are all about.
Good Hunting :salute:

[Rockin Robbins]

When you're first starting out I recommend that you leave map contacts on. Then with your pencil, plot a target position, then another position after 3 minutes. Measure the distance between the two points with your compass. The number of hundred yards between the two points is the speed in knots.

Now you can extend a line between the two points and forward in the direction of travel. With your protractor you can measure the target's course.

This is MUCH more accurate than the stadimeter auto speed and course thing, which is ALWAYS wrong.

If you wish, you can transition to finding the two positions with stadimeter and plotting them manually with map contacts off. Or you can find the 2 positions by active sonar and manually plot them.

I find that map contacts on is just as historically accurate so long as you are equipped with radar. Real radar gave more accurate measurements than our game with map contacts on anyway because the radar was analog and the game has binning from its digital nature.

They also had an entire crew assisting them, a whole collections of tools we don't have a clue about in the game and binocular vision with peripheral capability giving them a much fuller perception of their environment than we have. At best, SH4 lets you experience some of the experience, make some of the decisions and experience some of the dilemmas real submariners did.

But getting all nitpicky about realism is kinda foolish in a game where realism isn't on the menu. You can't even get cold and wet for 4 hours standing watch in freezing rain!

So play in a way that can teach you the concepts of torpedo targeting. That's about the extent of possible realism here anyway. Leave the map contacts on, especially at first. And consult the fun meter once in awhile. If it isn't at 75% or better, change the way you're playing.

[Dogfish40]

Damn Robbins,
If I had teachers like you when I was in school I would have been there a lot more! A compliment. Never stop your posts, I learn every time I read 'em.
Rock On :salute:
D40

[Jax von May]

:up::up:I want the nomograph in SH4 asap. Is there any way to get it in?

Loved it in SH3..

This is Wazoo's nomograph mod for SH3

http://i4.photobucket.com/albums/y136/wazooda/findknots.jpg


The 3 lines at the bottom is the nomograph. If you know any 2 values of the 3, you can discover the 3rd unknown value. If you know time travelled, and distance travelled, you can find speed. If you know speed and time travelled, you can find distance. All you need to do is make a line between the 2 known points, and the line will cross the 3rd line where you will find the value you were looking for.
Quite ingenious.