How to estimate speed?

NiceSub · 12-24-10, 05:00 AM

Hello,
I watched so much tutorials etc..but i dont get how to calculate speed and how to use stopwatch.When i press it it says no enough data and yet u put AOB then via stedimeter get range and position keper is on and target is locked.What i am messing?Is there also some kind of formula??
Please if you write formula explain all math operation and also give some example with numbers and how to optainn that data used in formula.dont youst simply write me formula caouse english is not my mother language and i strugle then to undestand formula.
thnx in advance

razark · 12-24-10, 11:49 AM

To use the stopwatch con to obtain speed, you need to do two bearing/ranges fixes with a period of time between them.

You can also mark the ship's position on the map. Wait three minutes, and mark the position again. The distance will give you the speed. If the ship traveled 700 yards, the speed is 7 knots. If it traveled 2000 yards, it traveled 20 knots. Every 100 yards traveled in three minutes is one knot of speed.

I'm goin' down · 12-24-10, 12:42 PM

Razark's description of the 3 minutes rule is the easiest for computing speed.

Aternatively, divide the distance (in yards) by number of seconds and get the distance per second. Mulitply by 180 (i.e. 3 minutes expressed in seconds) to determine speed. The alternative is useful when you have not measured distance in terms of full minutes. Keep a calulator handy to save time calculating.

General rule: The longer the time used to meausre distnace, the more accurate the speed calculation. Note: firing at long range requires a speed be calcualted accurately to ensure the torpedoes hit the target, even under O'Kane.

Pisces · 12-24-10, 02:40 PM

And if you know the length of the target you can time how long it takes to pass through a fixed periscope line. Fixed meaning it doesn't turn, and neither should your boat. If you point it at a bearing anything other than 0 or 180 degrees then your own speed will affect the result. So to avoid that you have to turn your bow or stern to just in front of the target and time the start and finnish of passing the line. Then divide length in yards by time in seconds. To convert that to knots double the result and add one tenth of it.

If you know length in meters then just double the value (not adding one tenth) to get knots.

Soundman · 12-24-10, 06:10 PM

Welcome to the forums Nicesub ! First, just to be sure you know, use "X" on the keyboard to bring up the Chromometer (Stopwatch). Good advice has been given above. The most accurate will be by plotting on the map and marking the ship and measuring distance against the time. Here is a way to be very accurate....

If you have radar: When you first see (or are notified) a radar contact, go to the navmap and bring up the Chrono (X on keyboard).. Zoom in on the contact seen on the map. The contact will be updated with a new postion every 20 seconds or so, and when it's gets updated the contact will jump to a new position on the map. Get ready now! Hold your mouse over the button on the Chrono in anticipation, and as soon as you see the contact jump on the map again, immediately click the button on the chrono to start it. Quickly now, click on the black pencil (map tool in the lower left corner of the screen) and mark the position of the contact before it jumps again. Watch the chrono and mark the contact again at three minutes. At this point, it's a good idea to use the "ruler" (another map tool in the lower left corner) and draw a line from the first mark through the second mark and extend it a fair distance, as this will give you the course of the target. Now, measure the distance between the two marks (X's) on the navmap you made using the compass (also in the lower left on the screen). As stated above, 500yds=5knots, 1000yds=10 knots and so on....The longer time you have to measure the more accurate it will be. If you wait six minutes and measure the marks, divide by two to easily compute the speed. Example: if the distance is 1000 yds... 1000 divided by 2 = 500... 500 =5 knots...

Be aware, ships are not always traveling in whole numbers or even half numbers, but can be traveling in 10th's of a knot. It may depend on what mod you use. A couple years back or so, I debated this with a few people in a thread and the argument came about. I knew from experimenting, that a boats speed could vary in fine increments of speed. I was using the RSRDC Mod at the time and "Lurker" (creator of the mod) confirmed this... So, the bottom line is, if you want precision, especially for a long distance shot, you need to to nail down the speed as best you can.. It takes a little practice, but with a little patience, you'll be a good Skipper in no time at all. Good Luck!

EDIT: BTW, out of curiousity I dug up one of the old threads (there were more than one) on this subject of fractions of knots and here it is:

http://www.subsim.com/radioroom/show...ction+of+knots

Armistead · 12-24-10, 06:49 PM

You can use the pause button if needed and the tools still work to make markings, sometime this is helpfu calculating speed with the 3 min rule.

I have read lurker did use fractions, I'm sure with another tool as I don't think fractions are included in the ME, but I think lurker used python or notepad doing a lot of his work. The only issue is you can't use fractions setting speed, so not sure why it matters.

NiceSub · 12-25-10, 07:57 AM

Can somebody give me insructions how to use hydrophone?How to know is he far or close?And things like that

Armistead · 12-25-10, 08:49 AM

Go to the top search on the right and type "Hydrophones". You'll get about 1000 threads on the subject.

12-24-10, 05:00 AM	#1
NiceSub Torpedoman Join Date: Dec 2010 Posts: 112 Downloads: 66 Uploads: 0	How to estimate speed? Hello, I watched so much tutorials etc..but i dont get how to calculate speed and how to use stopwatch.When i press it it says no enough data and yet u put AOB then via stedimeter get range and position keper is on and target is locked.What i am messing?Is there also some kind of formula?? Please if you write formula explain all math operation and also give some example with numbers and how to optainn that data used in formula.dont youst simply write me formula caouse english is not my mother language and i strugle then to undestand formula. thnx in advance

12-24-10, 11:49 AM	#2
razark Ocean Warrior Join Date: Mar 2007 Location: Houston, TX Posts: 2,731 Downloads: 393 Uploads: 12	To use the stopwatch con to obtain speed, you need to do two bearing/ranges fixes with a period of time between them. You can also mark the ship's position on the map. Wait three minutes, and mark the position again. The distance will give you the speed. If the ship traveled 700 yards, the speed is 7 knots. If it traveled 2000 yards, it traveled 20 knots. Every 100 yards traveled in three minutes is one knot of speed. __________________ "Never ask a World War II history buff for a 'final solution' to your problem!"

12-24-10, 12:42 PM	#3
I'm goin' down Ocean Warrior Join Date: Sep 2008 Location: Notify command we have entered the Grass Sea Posts: 2,822 Downloads: 813 Uploads: 0	formula Razark's description of the 3 minutes rule is the easiest for computing speed. Aternatively, divide the distance (in yards) by number of seconds and get the distance per second. Mulitply by 180 (i.e. 3 minutes expressed in seconds) to determine speed. The alternative is useful when you have not measured distance in terms of full minutes. Keep a calulator handy to save time calculating. General rule: The longer the time used to meausre distnace, the more accurate the speed calculation. Note: firing at long range requires a speed be calcualted accurately to ensure the torpedoes hit the target, even under O'Kane.

12-24-10, 02:40 PM	#4
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	And if you know the length of the target you can time how long it takes to pass through a fixed periscope line. Fixed meaning it doesn't turn, and neither should your boat. If you point it at a bearing anything other than 0 or 180 degrees then your own speed will affect the result. So to avoid that you have to turn your bow or stern to just in front of the target and time the start and finnish of passing the line. Then divide length in yards by time in seconds. To convert that to knots double the result and add one tenth of it. If you know length in meters then just double the value (not adding one tenth) to get knots. __________________ My site downloads: https://ricojansen.nl/downloads

12-24-10, 06:10 PM	#5
Soundman Commodore Join Date: Jul 2006 Location: Orlando, Fl Posts: 617 Downloads: 60 Uploads: 0	Welcome to the forums Nicesub ! First, just to be sure you know, use "X" on the keyboard to bring up the Chromometer (Stopwatch). Good advice has been given above. The most accurate will be by plotting on the map and marking the ship and measuring distance against the time. Here is a way to be very accurate.... If you have radar: When you first see (or are notified) a radar contact, go to the navmap and bring up the Chrono (X on keyboard).. Zoom in on the contact seen on the map. The contact will be updated with a new postion every 20 seconds or so, and when it's gets updated the contact will jump to a new position on the map. Get ready now! Hold your mouse over the button on the Chrono in anticipation, and as soon as you see the contact jump on the map again, immediately click the button on the chrono to start it. Quickly now, click on the black pencil (map tool in the lower left corner of the screen) and mark the position of the contact before it jumps again. Watch the chrono and mark the contact again at three minutes. At this point, it's a good idea to use the "ruler" (another map tool in the lower left corner) and draw a line from the first mark through the second mark and extend it a fair distance, as this will give you the course of the target. Now, measure the distance between the two marks (X's) on the navmap you made using the compass (also in the lower left on the screen). As stated above, 500yds=5knots, 1000yds=10 knots and so on....The longer time you have to measure the more accurate it will be. If you wait six minutes and measure the marks, divide by two to easily compute the speed. Example: if the distance is 1000 yds... 1000 divided by 2 = 500... 500 =5 knots... Be aware, ships are not always traveling in whole numbers or even half numbers, but can be traveling in 10th's of a knot. It may depend on what mod you use. A couple years back or so, I debated this with a few people in a thread and the argument came about. I knew from experimenting, that a boats speed could vary in fine increments of speed. I was using the RSRDC Mod at the time and "Lurker" (creator of the mod) confirmed this... So, the bottom line is, if you want precision, especially for a long distance shot, you need to to nail down the speed as best you can.. It takes a little practice, but with a little patience, you'll be a good Skipper in no time at all. Good Luck! EDIT: BTW, out of curiousity I dug up one of the old threads (there were more than one) on this subject of fractions of knots and here it is: http://www.subsim.com/radioroom/show...ction+of+knots __________________ RVAH-9 RA-5C Vigilante at NAS Sanford, Fl 1966 The coolest plane few have heard of! Last edited by Soundman; 12-24-10 at 06:32 PM.

12-24-10, 06:49 PM	#6
Armistead Rear Admiral Join Date: Dec 2008 Location: on the Dan Posts: 10,880 Downloads: 364 Uploads: 0	You can use the pause button if needed and the tools still work to make markings, sometime this is helpfu calculating speed with the 3 min rule. I have read lurker did use fractions, I'm sure with another tool as I don't think fractions are included in the ME, but I think lurker used python or notepad doing a lot of his work. The only issue is you can't use fractions setting speed, so not sure why it matters.

12-25-10, 07:57 AM	#7
NiceSub Torpedoman Join Date: Dec 2010 Posts: 112 Downloads: 66 Uploads: 0	Can somebody give me insructions how to use hydrophone?How to know is he far or close?And things like that

12-25-10, 08:49 AM	#8
Armistead Rear Admiral Join Date: Dec 2008 Location: on the Dan Posts: 10,880 Downloads: 364 Uploads: 0	Go to the top search on the right and type "Hydrophones". You'll get about 1000 threads on the subject.