Deducting speed from sonar.

Mr.Bimmler · 11-15-08, 04:30 PM

Hello,

Well, is it possible to deduct a ships sound from counting propellor revolutions of a ship? And how accurate are these estimates? I'd really like to know this, just to back up other ways of speed estimations.

Rockin Robbins · 11-15-08, 07:07 PM

Unfortunately not too accurate at all. The game only uses a few recordings for propeller noises. So beat frequency doesn't change continuously with changes in speed. In real life there wasn't any correlation chart to convert RPM to speed as there was no extensive database of such information like there is today.

About all they could do is say "moving fast" or "moving slow" or "speeding up" or "slowing down." It is possible on a very few warships that they had RPM/speed data. Even then they would have to have identified the ship to make any conclusions.

So I guess we're not crippled.

SteamWake · 11-15-08, 11:57 PM

Yes this topic comes up now and again.

Unfortunatly as RR said the game uses pre recorded 'samples' of sounds.

your best bet is to mark a spot.... wait a specific time... use the stop watch... mark again.... do a little math... and there you have the speed.

Mr.Bimmler · 11-16-08, 05:29 AM

Ah I understand. Maybe something the devs can implement in SH5?

Rockin Robbins · 11-16-08, 07:45 AM

Yup, synthesized instead of recorded prop sounds could accomplish that. Unfortunately, that leaves you with the remaining problem of how to correlate prop sounds with target speed, which WWII subs couldn't do. So it would be mostly useless information.

Soundman · 11-17-08, 03:23 PM

Of course the Nomograph is a good tool, but my favorite way to calculate speed is to use a calculator to get precise measurements. For example, a ship traveling 1.3 NM's in 5 minutes:

1.- 60 (minutes always start here) divided by 5 (Travel time) = 12
2.- 12 X 1.3 (distance) = 15.6 (Speed)

So you have this formula: 60 divided by (time) X (distance) = speed

A little thing to keep in mind is, if you use 6 minutes as your time measurement, you don't need the calculator, just move the distance measurement a decimal point to get the speed. Example: A boat traveling .5 miles in 6 minutes will get you 5 knots speed. 60 divided by 6 = 10.. ..10 X .5 = 5 So simple even a caveman can do it

This works well for precision. Some will say "Ah, just round it to the nearest even number". I say, "hell no!" ... I want my speed calculated to at least the nearest 1/4 nautical mile per hour. Many times that can be the difference between a miss or hit. If a boat is moving a constant speed and course and I have ample time, I always hit exactly where I'm aiming using this technique. It becomes extremely accurate when using the Dick O'Kane method of targeting. If you don't know about the "O'Kane" method, search these forums, you won't regret it. Some time back Rockin Robbins had a video tutorial on this method I'd strongly recommend viewing.

11-15-08, 04:30 PM	#1
Mr.Bimmler Swabbie Join Date: Oct 2008 Location: Meinhead Posts: 5 Downloads: 23 Uploads: 0	Deducting speed from sonar. Hello, Well, is it possible to deduct a ships sound from counting propellor revolutions of a ship? And how accurate are these estimates? I'd really like to know this, just to back up other ways of speed estimations.

11-15-08, 07:07 PM	#2
Rockin Robbins Navy Seal Join Date: Mar 2007 Location: DeLand, FL Posts: 8,900 Downloads: 135 Uploads: 52	Unfortunately not too accurate at all. The game only uses a few recordings for propeller noises. So beat frequency doesn't change continuously with changes in speed. In real life there wasn't any correlation chart to convert RPM to speed as there was no extensive database of such information like there is today. About all they could do is say "moving fast" or "moving slow" or "speeding up" or "slowing down." It is possible on a very few warships that they had RPM/speed data. Even then they would have to have identified the ship to make any conclusions. So I guess we're not crippled. __________________ Sub Skipper's Bag of Tricks, Slightly Subnuclear Mk 14 & Cutie, Slightly Subnuclear Deck Gun, EZPlot 2.0, TMOPlot, TMOKeys, SH4CMS

11-16-08, 07:45 AM	#5
Rockin Robbins Navy Seal Join Date: Mar 2007 Location: DeLand, FL Posts: 8,900 Downloads: 135 Uploads: 52	Yup, synthesized instead of recorded prop sounds could accomplish that. Unfortunately, that leaves you with the remaining problem of how to correlate prop sounds with target speed, which WWII subs couldn't do. So it would be mostly useless information. __________________ Sub Skipper's Bag of Tricks, Slightly Subnuclear Mk 14 & Cutie, Slightly Subnuclear Deck Gun, EZPlot 2.0, TMOPlot, TMOKeys, SH4CMS

11-15-08, 11:57 PM	#3
SteamWake Rear Admiral Join Date: Mar 2005 Posts: 13,224 Downloads: 5 Uploads: 0	Yes this topic comes up now and again. Unfortunatly as RR said the game uses pre recorded 'samples' of sounds. your best bet is to mark a spot.... wait a specific time... use the stop watch... mark again.... do a little math... and there you have the speed.

11-16-08, 05:29 AM	#4
Mr.Bimmler Swabbie Join Date: Oct 2008 Location: Meinhead Posts: 5 Downloads: 23 Uploads: 0	Ah I understand. Maybe something the devs can implement in SH5?

11-17-08, 03:23 PM	#6
Soundman Commodore Join Date: Jul 2006 Location: Orlando, Fl Posts: 617 Downloads: 60 Uploads: 0	Of course the Nomograph is a good tool, but my favorite way to calculate speed is to use a calculator to get precise measurements. For example, a ship traveling 1.3 NM's in 5 minutes: 1.- 60 (minutes always start here) divided by 5 (Travel time) = 12 2.- 12 X 1.3 (distance) = 15.6 (Speed) So you have this formula: 60 divided by (time) X (distance) = speed A little thing to keep in mind is, if you use 6 minutes as your time measurement, you don't need the calculator, just move the distance measurement a decimal point to get the speed. Example: A boat traveling .5 miles in 6 minutes will get you 5 knots speed. 60 divided by 6 = 10.. ..10 X .5 = 5 So simple even a caveman can do it This works well for precision. Some will say "Ah, just round it to the nearest even number". I say, "hell no!" ... I want my speed calculated to at least the nearest 1/4 nautical mile per hour. Many times that can be the difference between a miss or hit. If a boat is moving a constant speed and course and I have ample time, I always hit exactly where I'm aiming using this technique. It becomes extremely accurate when using the Dick O'Kane method of targeting. If you don't know about the "O'Kane" method, search these forums, you won't regret it. Some time back Rockin Robbins had a video tutorial on this method I'd strongly recommend viewing.