TARGET SPEED, searching for the magic bullet

greyrider · 02-11-09, 10:13 AM

i think i have found it, im working on it, may take a week and, it may take longer, but i made a mission to test
this formula from the torpedo fire control manual, using the procedure explained by the FCM, using just the hydrophones to determine target speed. it works like a charm,
i just need to test it alittle more at extreme hydrophone range, 18.9 nm. i wont post again, until i have it down pat, but as soon as i do, i will present it to you, in a post, and in a mission.

formula is:

SS x(sin LA) / (sin AB)
where
ss = sub speed
la = lead angle
ab = angle on bow

Rockin Robbins · 02-11-09, 12:35 PM

Are you defining lead angle as the bearing to target expressed in number of degrees from the bow, as in the German bearing system?

If so, you're onto something with some playing around. All by itself, it means nothing. BUT if you put yourself on a collision course with the target, that is the bearing to target doesn't change over time, THEN his speed is a known proportion of yours based on the Angle on the Bow. (unless his AoB is zero or 180, in which case the target speed is undefined)

I don't have my drawing software right here at work, but I could work it up and shoot you the diagram for you to troubleshoot the rest of the way if you'd like. You're onto something really useful here.

DarkFish · 02-11-09, 02:38 PM

Quote:

Originally Posted by greyrider

...
using just the hydrophones to determine target speed
...

SS x(sin LA) / (sin AB)
where
ss = sub speed
la = lead angle
ab = angle on bow

Isn't it a bit hard to determine the AOB with only your hydrophones

I don't know what kind of hydrophones you've got but mine only give the bearing

Ah well maybe its just an American superweapon for a change, the japs have got UFOs and such, so it'd only be fair if the US have got superpowered hydrophones:rotfl:

Rockin Robbins · 02-11-09, 03:21 PM

Uh DarkFish, it isn't nice to make fun of others. Especially when the ignorance is yours. Greyrider is on solid ground here.

I shall draw a mental picture and see if you can get up to speed here. With your sonar, you determine a bearing to the target. A simple ping will give you a range. Range plus bearing equals position. Plot the position. Three minutes later, ping again. Range plus bearing equals position number two. Connecting the two positions and extending in the direction of travel gives the target track. With the protractor, clicking ahead of the target position on the track, clicking again on the target position and a third time in the middle of your sub position, you can read the AoB right off the nav map. By inspection with the compass rose on the end of the ruler with help on you can read the target's course. The number of hundred yards between the two positions is the target speed in knots. No superweapons, UFOs, or cute puppies were harmed in this procedure.

Note that the target speed is not necessary to derive the course or AoB. Greyrider is working out another way to determine the speed without plotting two positions 3 minutes apart. I can see this being useful for a visual target where you could use his Mark 1 Eyeball method of measuring AoB. Greyrider is brainstorming here on the message board, and the number one rule of brainstorming is that wacky ideas are encouraged and enthusiastically followed up to see where they lead. We whack people who make fun of ideas over the head with a belaying pin.

AVGWarhawk · 02-11-09, 03:23 PM

Yes, RR, that is how you can get the track of the vessel and formulate the AOB relatively accurately

DarkFish · 02-11-09, 03:56 PM

Quote:

Originally Posted by Rockin Robbins

With your sonar, you determine a bearing to the target. A simple ping will give you a range.

Yeah i can see your point
My previous post indeed sounds a bit diminishing, it wasn't meant that way.
If anyone feels hurt I'm sorry for it.
I just thought Greyrider meant using passive sonar only (hydrophones is passive sonar only, isn't it, or am I completely wrong here

)
Using passive sonar only it'd be completely impossible to determine AOB.
But now that I understand what he is meaning I can definately see the use of this formula, it'd be a very accurate and easy way of determining the targets speed.
So keep up the brainstorming and don't mind about people like me joking about UFOs

Rockin Robbins · 02-11-09, 04:06 PM

I just smell progress here. Even if an idea turns out to be positively lousy, often it leads to productive directions. Just ask Ducimus. Oh, you can't.

Armistead · 02-12-09, 04:17 PM

I just found this...I just asked the basic same question in another thread. I've been trying to figure out how to track aob and speed with sonar.

I would ping, mark bearing and range on the map. I don't know if the 3 minute rule applies or not, but ping again at 3 minutes, mark on the map range and distance.
My speed is zero and don't see how it can be done if your sub is moving.

I just didn't know if this rule worked to determine speed. Now I see it's easily possible to get AOB.

Course the problem is TF...ping, and it's a new ball game. If you get this figured out, someone please sticky it.

Pisces · 02-12-09, 07:46 PM

Quote:

Originally Posted by DarkFish

Quote:

Originally Posted by Rockin Robbins

With your sonar, you determine a bearing to the target. A simple ping will give you a range.

Yeah i can see your point
My previous post indeed sounds a bit diminishing, it wasn't meant that way.
If anyone feels hurt I'm sorry for it.
I just thought Greyrider meant using passive sonar only (hydrophones is passive sonar only, isn't it, or am I completely wrong here

)
Using passive sonar only it'd be completely impossible to determine AOB.
But now that I understand what he is meaning I can definately see the use of this formula, it'd be a very accurate and easy way of determining the targets speed.
So keep up the brainstorming and don't mind about people like me joking about UFOs

It's NOT impossible to determine AOB with passive hydrophone listening. It maybe not a quick thing to do. And being stationary simplifies alot (just like sckallst mentioned) But certainly possible. Look to the following thread:

http://www.subsim.com/radioroom/showthread.php?t=110619
(further down the thread are links to a video)

Or if you want to take a shortcut for such a drawing with a handheld tool:

http://www.subsim.com/radioroom/show...0&postcount=14

(or this one, works the same, but linear as opposed to the circular above:
http://www.subsim.com/radioroom/show...0&postcount=10)

02-11-09, 10:13 AM	#1
greyrider Watch Officer Join Date: Apr 2005 Location: massachusetts Posts: 334 Downloads: 237 Uploads: 0	TARGET SPEED, searching for the magic bullet i think i have found it, im working on it, may take a week and, it may take longer, but i made a mission to test this formula from the torpedo fire control manual, using the procedure explained by the FCM, using just the hydrophones to determine target speed. it works like a charm, i just need to test it alittle more at extreme hydrophone range, 18.9 nm. i wont post again, until i have it down pat, but as soon as i do, i will present it to you, in a post, and in a mission. formula is: SS x(sin LA) / (sin AB) where ss = sub speed la = lead angle ab = angle on bow __________________ Her gun crew had guts, however, for from her canting bow came a half dozen well-aimed rounds. How they pointed and trained their gun on that tilting platform will long remain a wonder, and their dedication in keeping up the fire until they went under would be a matter of pride to any nation. O'Kane, Richard. Clear the Bridge!: The War Patrols of the U.S.S. Tang

02-11-09, 12:35 PM	#2
Rockin Robbins Navy Seal Join Date: Mar 2007 Location: DeLand, FL Posts: 8,900 Downloads: 135 Uploads: 52	Are you defining lead angle as the bearing to target expressed in number of degrees from the bow, as in the German bearing system? If so, you're onto something with some playing around. All by itself, it means nothing. BUT if you put yourself on a collision course with the target, that is the bearing to target doesn't change over time, THEN his speed is a known proportion of yours based on the Angle on the Bow. (unless his AoB is zero or 180, in which case the target speed is undefined) I don't have my drawing software right here at work, but I could work it up and shoot you the diagram for you to troubleshoot the rest of the way if you'd like. You're onto something really useful here. __________________ Sub Skipper's Bag of Tricks, Slightly Subnuclear Mk 14 & Cutie, Slightly Subnuclear Deck Gun, EZPlot 2.0, TMOPlot, TMOKeys, SH4CMS

02-11-09, 03:21 PM	#4
Rockin Robbins Navy Seal Join Date: Mar 2007 Location: DeLand, FL Posts: 8,900 Downloads: 135 Uploads: 52	Uh DarkFish, it isn't nice to make fun of others. Especially when the ignorance is yours. Greyrider is on solid ground here. I shall draw a mental picture and see if you can get up to speed here. With your sonar, you determine a bearing to the target. A simple ping will give you a range. Range plus bearing equals position. Plot the position. Three minutes later, ping again. Range plus bearing equals position number two. Connecting the two positions and extending in the direction of travel gives the target track. With the protractor, clicking ahead of the target position on the track, clicking again on the target position and a third time in the middle of your sub position, you can read the AoB right off the nav map. By inspection with the compass rose on the end of the ruler with help on you can read the target's course. The number of hundred yards between the two positions is the target speed in knots. No superweapons, UFOs, or cute puppies were harmed in this procedure. Note that the target speed is not necessary to derive the course or AoB. Greyrider is working out another way to determine the speed without plotting two positions 3 minutes apart. I can see this being useful for a visual target where you could use his Mark 1 Eyeball method of measuring AoB. Greyrider is brainstorming here on the message board, and the number one rule of brainstorming is that wacky ideas are encouraged and enthusiastically followed up to see where they lead. We whack people who make fun of ideas over the head with a belaying pin. __________________ Sub Skipper's Bag of Tricks, Slightly Subnuclear Mk 14 & Cutie, Slightly Subnuclear Deck Gun, EZPlot 2.0, TMOPlot, TMOKeys, SH4CMS

02-11-09, 03:23 PM	#5
AVGWarhawk Lucky Jack Join Date: Jun 2005 Location: In a 1954 Buick. Posts: 28,257 Downloads: 90 Uploads: 0	Yes, RR, that is how you can get the track of the vessel and formulate the AOB relatively accurately __________________ “You're painfully alive in a drugged and dying culture.” ― Richard Yates, Revolutionary Road

02-11-09, 04:06 PM	#7
Rockin Robbins Navy Seal Join Date: Mar 2007 Location: DeLand, FL Posts: 8,900 Downloads: 135 Uploads: 52	I just smell progress here. Even if an idea turns out to be positively lousy, often it leads to productive directions. Just ask Ducimus. Oh, you can't. __________________ Sub Skipper's Bag of Tricks, Slightly Subnuclear Mk 14 & Cutie, Slightly Subnuclear Deck Gun, EZPlot 2.0, TMOPlot, TMOKeys, SH4CMS

02-12-09, 04:17 PM	#8
Armistead Rear Admiral Join Date: Dec 2008 Location: on the Dan Posts: 10,880 Downloads: 364 Uploads: 0	I just found this...I just asked the basic same question in another thread. I've been trying to figure out how to track aob and speed with sonar. I would ping, mark bearing and range on the map. I don't know if the 3 minute rule applies or not, but ping again at 3 minutes, mark on the map range and distance. My speed is zero and don't see how it can be done if your sub is moving. I just didn't know if this rule worked to determine speed. Now I see it's easily possible to get AOB. Course the problem is TF...ping, and it's a new ball game. If you get this figured out, someone please sticky it.