Speedometer Precision

[davidbadke]

Whenever I try to calculate a target's speed manually. I'm always off by 0.5-1 knots. I think it's because I can't know my own ships speed to any more than one significant digit. So is there any way to know you own ship's speed with more precision? Thanks in advance.

[19Herr_Rapp86]

Really if you're calculating a ships speed within a half to a full knot accurate, you're doing something right, my friend. Most of my calculations are within that range and it doesn't really affect my impact points at all (Dick O'Kane targeting method) If you have a half to full knot deviation from true target speed, you're good to go, skip. In the 1940's you're not going to have pinpoint accuracy. I also play Sub Command every now and again. It involves modern nuke-powered boats. Instead of the TDC it is a computer called target motion analyses (TMA). Still depends on sonar readings and whatnot to get estimated (keyword) depth, speed, range, etc. Not 100% to the gnats-you-know-what accurate. If there was such a thing as 100% accuracy there would be no need for acoustic homing torpedoes ;)

[doulos05]

Are you using the 3 minute rule w/ your radar? Radar jumps (because it's sweeping). The timing of the jumps is likely the cause for the error. But, as he said, at the ranges you should be shooting at (1,500 tops), 1 knot of error in speed is nothing.

[the.terrabyte.pirate]

Confirmation please:-

For imperial measurements "Feet / miles" = Knots is a 3 minute rule.

For metric measurements "Meters / Kilometers" = Knots is a 3 min 15 second rule.

Thanks,

[SuperEtendard]

Really if you're calculating a ships speed within a half to a full knot accurate, you're doing something right, my friend. Most of my calculations are within that range and it doesn't really affect my impact points at all (Dick O'Kane targeting method) If you have a half to full knot deviation from true target speed, you're good to go, skip. In the 1940's you're not going to have pinpoint accuracy. I also play Sub Command every now and again. It involves modern nuke-powered boats. Instead of the TDC it is a computer called target motion analyses (TMA). Still depends on sonar readings and whatnot to get estimated (keyword) depth, speed, range, etc. Not 100% to the gnats-you-know-what accurate. If there was such a thing as 100% accuracy there would be no need for acoustic homing torpedoes ;)

In which year is set Sub Command?, because I think that the subs (not only nuclear, conventional too) in 2012 have really powerfull sonars and great computers that can calculate the data and a 99% precise solution, if in the 90's the airplanes' radar s could guide a missile within a pair of meters error, and nowadays they have almost none-error at houndreds of kilometers, with fast, moving targets.... i think the Subs have bettter technologies, their are much bigger. I dont know if there are radar guided torpedoes, but homing is still necesary because the target sub can maneouver, much more than our Balao would ever dream hahaha (30 knts, + 300 mts depth).

[19Herr_Rapp86]

My point being its still not 100% precise. Guided missiles still miss the pinpoint. Within meters. Not right on the money. My point was that its not going to be to the fraction of a thousandth of a decimal accurate in the 1940's on speed calculation, and gave an example of modern tech that was still not 100% on the numbers accurate. In WWII era, calculating to a half a knot to a full knot deviation, as he said he was calculating, in 1941, that is precision.

[twm47099]

Confirmation please:-

For imperial measurements "Feet / miles" = Knots is a 3 minute rule.

For metric measurements "Meters / Kilometers" = Knots is a 3 min 15 second rule.

Thanks,
Imperial: (yards in 3 minutes)/100=kts

(actually it is number of yards in 2 min 58 seconds, so there is already a very small error.)

Tom

[Ruff EL]

Are you using the 3 minute rule w/ your radar? Radar jumps (because it's sweeping). The timing of the jumps is likely the cause for the error. But, as he said, at the ranges you should be shooting at (1,500 tops), 1 knot of error in speed is nothing.

uuuhh, ranges of 8-8500 yd shots are just as likely to hit as 1500 yd shots if you get your calculations done properly

[doulos05]

uuuhh, ranges of 8-8500 yd shots are just as likely to hit as 1500 yd shots if you get your calculations done properly

an 8,000 yard shot requires more precise measurements than a 1500 yard shot. 5 to 7 times as precise, in fact. Consider, I've measured target A and target B's speed to be 10 knots. Target A is 1,500 yards away, target B is 8,000 yards away. Both target's actual speed is 11 knots.

For a fast torpedo fired at Target A, the torpedo will run for 58.7 seconds, give or take. We'll round that up to 1 minute to account for time to accelerate to leave the tube and accelerate to speed.

For a slow torpedo fired at Target B, the torpedo will run for 400 seconds, we won't round that because it's a nice round number already, but it's probably closer to 402 or 404 seconds.

Now, Target A runs for 1 minute at 1 knot faster than we measured. He only travels 33 yards farther than we estimated, which means shots aimed at Bow hit MoT, shots aimed at MoT hit stern, and shots aimed at stern miss astern.

Target B, on the other hand runs for 6 2/3s times longer. It travels nearly 220 yards. For reference, Liberty ships had a waterline hull length of 150 yards. All that from a 1 knot error in speed estimation.

Similarly, 1 degree of error in target position results in a miss of aimed target of 50 feet per 1,000 yards. Or, in this case 75 feet for Target A (still a hit, but aft of target) or 400 feet for Target B (nearly the length of a Liberty Ship).

One degree of error in measured AoB moves our projected impact point by a similar margin, through it's impact is harder to figure because we're dealing with the distance between two points on two different triangles. It's smaller than the error for target position, but it's still noticeable.

A formula is only as good as the input you give it and thanks for advanced math and calculus, we know that every measurement we take introduces a small amount of error into the input. The variable with the most direct control over the impact of those errors is range, therefore many people seek to reduce that variable as much as possible to reduce the size of the inevitable errors they introduce through measurements.

[P_Funk]

uuuhh, ranges of 8-8500 yd shots are just as likely to hit as 1500 yd shots if you get your calculations done properly
The top scoring U-boat ace for Germany preferred the notion of "1 shot, 1 ship". He could manage this because he fired from 500 to 800 meters from within the columns of a convoy.

The top scoring fighter ace for Germany (also top scoring ace ever) said "I only ever fired when the enemy filled my windscreen".

The sniper with the most confirmed kills in history used iron sights and fired from much shorter range than Carlos Hathcock tended to.

You can do just about anything from the maximum realistic range, they're just rarely ever going to give you a medal for it. If you are consistently shooting at that range then you're either desperate, incompetent, or just exercising poor decision making skills (not literally you, just the theoretical captain).

Calculations can be that accurate, but in the 40s, the instruments didn't even afford a competent commander the ability to fire beyond 1000 without using a spread in order to feel certain of a hit.

Lets also not forget this:
At 15:57 on 2 May, Conqueror fired three 21 inch Mk 8 mod 4 torpedoes (conventional, non-guided, torpedoes), each with an 805-pound (363 kg) Torpex warhead. While the Conqueror was also equipped with the newer Mark 24 Tigerfish homing torpedo, there were doubts about its reliability. Two of the three torpedoes hit the General Belgrano.Thats a nuclear submarine in 1982. :arrgh!:

[Ruff EL]

well no offense, but you guys are overthinking your calculations. You dont need any advanced math to work the TDC in this game. All tools are provided on the nav map. If you play with no map contacts enabled this gets considerably more difficult and advanced math becomes more necessary. However, with all settings on except no map contacts (which still equates to 100% realism according to the dificulty menu), all you need to do is the 3 minute rule for speed (even off a half knot wont affect your spread too much, and yes you do need spreads at those ranges), and you yourself draw the targets track and extend it out......watching the contacts over time (on the nav map) will give you a 99.9% accurate target course as well as AoB (using the protractor to draw an angle from your sub to the target then extended along the targets course)and speed, this of course is done with the minute corrections required to the already drawn indicators on your map.....once you get a "generalized" solution with speed/range/aob you can watch the attack maps generated target track and again refine your measurements. Your goal is to get the small black target line on the attack map to coincide with the movement of the black dot (in TMO) or ship silhouette (stock).

this process is quite simple, and impossible in a scenario when you are detected or underfire, and very effective to perform long range shots on large convoys/task forces and slipping away before the escorts even know whats on the way (unless they spot the wakes of course).

All it takes is a little refinement of a general solution to achieve a 95% effective solution. This, I am well aware of, is technique not available to WW2 captains and thus is unrealistic, but this game is already full of things that werent available so play it how you want to play it, its your game.

I have gotten it down to a science where i can fire 2 spreads of 3 at 2 seperate targets and get hits on both at the same time to avoid potential evasive maneuvers. Then get away, sometimes even surfaced, completely undetected and unharmed. About the only downside is not seeing the booms and sinkings up close, or if you happen to spend all that time gaining the firing solution/refining it and firing your fish and then you see them all start a zig in their course or just a blatant course change, that can be frustrating, but at least your alive to fight another day.

P.S. early war boats have almost no chance of achieving 1 shot 1 kill statistics. Ive fired spreads of 4 front and 4 rear tubes with 7 duds and a circle runner before.....THAT is frustrating! lol

This talk of timing speeds and hitting anything other than the MoT is just a bunch of extra info in your head you only need if your trying to show off, IMO. I dont even use fast 90 or O'kane methods, i can do it all close range or from any angle just as i described above from 8000+ yards.

bottom line: play how u wanna play, if your inclined to learn manual targeting, learn it the way that suits you best, it just takes a little familiarization of the tools that you have at hand.

[Armistead]

I tend to agree 1 knot isn't gonna mess you up short range, but can long range, even the 3 minute rule can be off .5 knot, got to zoom in close and be precise.

With many mods, waves can effect the ships speed anyway, so it may actually vary a knot in it's speed as it travels.

Not to mention if using M14's, they often see your torp wake and with the turbo stops and starts easy to dodge one torp.....

Long range I shoot spreads.


I find the best AOB is plot his course, you can set the course on the AOB wheel and it's a perfect AOB, no drawing triangles. If you do it the stad way with accurate measurements, it will give you course and speed, just spin the wheel and set the course given on the AOB wheel..I prefer marking lines on the map

[Ruff EL]

I tend to agree 1 knot isn't gonna mess you up short range, but can long range, even the 3 minute rule can be off .5 knot, got to zoom in close and be precise.

With many mods, waves can effect the ships speed anyway, so it may actually vary a knot in it's speed as it travels.

Not to mention if using M14's, they often see your torp wake and with the turbo stops and starts easy to dodge one torp.....

Long range I shoot spreads.


I find the best AOB is plot his course, you can set the course on the AOB wheel and it's a perfect AOB, no drawing triangles. If you do it the stad way with accurate measurements, it will give you course and speed, just spin the wheel and set the course given on the AOB wheel..I prefer marking lines on the map

elaborate again your AoB procedure please?......are you determining their course from the compass rose tool?

[TorpX]

Whenever I try to calculate a target's speed manually. I'm always off by 0.5-1 knots. I think it's because I can't know my own ships speed to any more than one significant digit. So is there any way to know you own ship's speed with more precision? Thanks in advance.

First, welcome aboard! :salute:


You raise a good question. I don't really know of a way to be sure of your own speed. I spent some time checking my boat's ability to hold course (when I was dabbling with celestial navigation) and the results were not encouraging. It would not surprise me if your true speed differed from your apparant speed by half a knot of so. Without some kind of independent markers/tools to check, I can't think of any way to know if your guage is accurate or not.

On second thought, one could time your boat's passage from one grid line to another on the nav map (zoomed in). This should tell you what you need to know.

[razark]

Whenever I try to calculate a target's speed manually. I'm always off by 0.5-1 knots.
How are you figuring the target's speed?

Beyond that, .5-1 knot accuracy is good enough for a hit if you're close enough or use a spread.

[magic452]

elaborate again your AoB procedure please?......are you determining their course from the compass rose tool?

Use the three minute rule three times, 9 minutes. This will give you a very accurate speed, down to a quarter knot. It will also give you a very accurate target course. Remember that radar updates are every 20 seconds. Start your measurements at an update.

Use the compass rose to get that course in degrees, remember this reading.

First set speed and send to TDC.

To set AoB turn the AoB data input dial about what you guess is the Aob and send to TDC. The target ship dial on the top left side will turn.

Adjust the data input dial till the target ship dial shows the very same target course that you read off the compass rose. With the PK on that course will remain constant, if it does you have perfect AoB.


You also have very good speed +/- 0.5 knots.

You can do all this off radar readings so you have 2/3 of your firing solution and haven't seen the target yet.
If you don't have radar yet sonar will give you the same result but will take a bit more work.

With the 3D TDC you can set range to your best guess and point the scope at the target, estimate from the nav. map, and the PK will track the target for you. Radar updates will show what you need to do to get a good firing solution.

If the target stays on course and the AoB doesn't change all you need is a couple of steadimeter readings for range when the target gets closer and your all set to go.

Magic

[doulos05]

Ruff El, you're still talking about small margins of error at 8,000 yards. I'm not arguing it can't be done, but it requires the use of spreads (either longitudinal or divergent) to guarantee hits. 1 degree of angle is equal to 140 yards at 8,000 yards. There are lots of ways to accumulate 1 degree of error in your target track over 8,000 yards. 0.5 knots of speed miscalculated, slightly missing the AoB. Missing the range by just a hair. Changes in target action after the shot.

[Armistead]

Use the three minute rule three times, 9 minutes. This will give you a very accurate speed, down to a quarter knot. It will also give you a very accurate target course. Remember that radar updates are every 20 seconds. Start your measurements at an update.

Use the compass rose to get that course in degrees, remember this reading.

First set speed and send to TDC.

To set AoB turn the AoB data input dial about what you guess is the Aob and send to TDC. The target ship dial on the top left side will turn.

Adjust the data input dial till the target ship dial shows the very same target course that you read off the compass rose. With the PK on that course will remain constant, if it does you have perfect AoB.


You also have very good speed +/- 0.5 knots.

You can do all this off radar readings so you have 2/3 of your firing solution and haven't seen the target yet.
If you don't have radar yet sonar will give you the same result but will take a bit more work.

With the 3D TDC you can set range to your best guess and point the scope at the target, estimate from the nav. map, and the PK will track the target for you. Radar updates will show what you need to do to get a good firing solution.

If the target stays on course and the AoB doesn't change all you need is a couple of steadimeter readings for range when the target gets closer and your all set to go.

Magic



Magic did a good job of explaining me, so I won't add much, but here are a few SS I once took.

I took about 3 stad readings {using SCAF}. Just finished the reading and asked for speed which gives you the speed of 8kts, course 60, so I accept speed and spin the AOB wheel and set it on 60. I use Easy AOB, which allows you to spin the dials freely, but you can adjust either way.

http://i651.photobucket.com/albums/uu235/Armistead1424/SH4Img2011-02-20_145414_109-1.jpg

So here on the map screen I had also been plotting his course with markings, notice his course is 60 true, that matches
my stad readings perfect.

http://i651.photobucket.com/albums/uu235/Armistead1424/SH4Img2011-02-20_145500_218.jpg

You can use stad, radar {3D radar a must} or visuals with 3 minute rule, depending if you have contacts on or off, but once you have his course, you basically have a perfect AOB. Won't add the attack SS's, but range was about 2000 yards, I shot 4,..I unlock and shoot by the wire, all hits bow to stern.

Course that goes out the window if he spots you, but if they just do the small helm zags, you still have his base course, just have to update speed and range.

[Stormende]

I am using TMO 2.5 with a 16:9 resolution monitor and visual speed calc is accurate at most. I can even get fractional readings but the sub has to be stopped and the measurement has to be done within 45 degrees of the point of impact. I tell you, this IS accurate; if I round it up, then I am off by 0.5 Knots. Not big deal if you launch one torp but if you use 3 then it is very noticiable, specially if you are engaging a target from over 4000 yards.

I use the 90 Fast attack method and to calc speed is (lengh of the target/time for the ship to pass) * 1.94

:salute: