Time to plot firing solution

[Bill Dickson]

Could someone please tell me the time to plot a firing solution from the initial contact.

1 In the real world

2 In the game



Thanks

Bill Dickson

[SeaQueen]

Could someone please tell me the time to plot a firing solution from the initial contact.

1 In the real world

2 In the game



Thanks

Bill Dickson

It depends. You can get a decent Ekelund range with two 5-10 minute legs in the game once you have contact on the sphere. I've given up trying to pull it off with the towed array. You end up getting okay but not great ranges.

I think this reflects reality fairly well. There's little things, but you can measure things accurately enough in the game to do pretty good in most cases.

There's other things, though that would allow you to achieve a solution faster. In the game there's DEMON, which allows you to figure out the range pretty fast from the bearing rate. You can lock down on someone almost as soon as you have broadband contact with that. DEMON exists in real life too. I'm not sure how reflective of real life the game's DEMON is.

In real life, they also can measure range using the Doppler shift. I wish we could do this in the game too. It'd make even a single narrow band tonal vicious.

[Wim Libaers]

There's other things, though that would allow you to achieve a solution faster. In the game there's DEMON, which allows you to figure out the range pretty fast from the bearing rate. You can lock down on someone almost as soon as you have broadband contact with that. DEMON exists in real life too. I'm not sure how reflective of real life the game's DEMON is.

The only real DEMON spectra I've found on the net are here, horrible quality.
http://www.fuzzytech.com/e/e_a_kumm.html
It appears it's different, line intensity apparently being more important than number of lines to determine blade count.

In real life, they also can measure range using the Doppler shift. I wish we could do this in the game too. It'd make even a single narrow band tonal vicious.

Wouldn't that be closure rate, not range? (of course, that would be helpful too to get the range)

A single tonal... Only if you know its frequency exactly. If, for example, they're not running the generators at the exact specified speed, you'd get errors.

[Neptunus Rex]

.....In real life, they also can measure range using the Doppler shift. I wish we could do this in the game too. It'd make even a single narrow band tonal vicious.

Incorrect. Doppler shift is solely a function of speed (own ships and/or target)in the "line of sight". Distance is not a factor. A measurable doppler shift at 5000 yards will be the same at 50,000 or 500,000 etc.

And yes, I too wish it were modeled. It is an accurate way to determine if a contact is opening or closing, manuevering away/towards, increasing/decreasing speed. ("Conn, Sonar, Possible target zig, Master One!")

[Sonoboy]

Doppler shift is modeled in the game. Look at a circle searching torpedo in NB.

[compressioncut]

Incorrect. Doppler shift is solely a function of speed (own ships and/or target)in the "line of sight". Distance is not a factor. A measurable doppler shift at 5000 yards will be the same at 50,000 or 500,000 etc.

And yes, I too wish it were modeled. It is an accurate way to determine if a contact is opening or closing, manuevering away/towards, increasing/decreasing speed. ("Conn, Sonar, Possible target zig, Master One!")

To be a little pedantic doppler is a function of relative speed when we are talking about target motion analysis. Actually, in any situation. A target does not have to increase its speed to display a doppler shift, as it can just turn toward or away from the sensor.

And doppler combined with relvel can give you a good firing solution in two updates (three minutes), and give you a very good appraisal of the situation after one ("TMA update!") - enough to send the helo out into a reasonable AOP and give the sub something to think about. The strip plotting used in the game is not the primary method of doing it - it's a check, and a good one, but it takes too long.

And again I'll reiterate what has been said, doppler is modelled in the game, but the displays we are given makes it not worthwhile to use, outside of fast moving/close range contacts like torps circling sonobuoys (up doppler pointer 03, down doppler pointer 07, CPA pointer 12. Whoopeee). That's OK, it wouldn't be useful to too many people and double the size of the manual.

[SeaQueen]

Incorrect. Doppler shift is solely a function of speed (own ships and/or target)in the "line of sight". Distance is not a factor. A measurable doppler shift at 5000 yards will be the same at 50,000 or 500,000 etc.


Doppler shift gives you the relative speed of the target.

You know your own speed so you can figure out the target's speed if you know the relative speed.

If you have the target's speed and the target's bearing rate, you have a good estimate of the target's range.

It's all about putting the pieces together. Knowing the target's speed can give you a pretty good range estimate very quickly. I don't know how much calculus you know, but here's how I think about it..

Pick a reference frame where you are stationary. In a very small instance of time, dt, your target (which is moving relative to you) travels a very small distance, ds. The target's speed v = ds/dt.

In that small instance of time the target's bearing changes by a small angle, dw. His bearing rate, BR = dw/dt. Now, by the definition of an angle, ds = R * dw. So, ds/dt = R * dw/dt. Therefore v = R * BR. So... R = v / BR. If you know the bearing rate and you know the speed, you've got his range.

You don't NEED to know his speed. You can do it with just bearings (see discussions of Ekelund ranging) but if you do have his speed, it's easy.

Ultimately it's all just your highschool geometry class.

[OKO]

Doppler effect have an impact depending on the course of the target relative to your position.

In simple words : if the target is going away, her frequency spectrum will be a bit higher than if the target is heading perpendicular to your position.
On the opposite, if the target is going away from you, her frequency spectrum will be a bit lower than if the target is heading perpendicular to your position.

the immediate information a doppler shift could give you for a target, is if this target (after beeing identified) is going toward (higher frequencies), perpendicular (normal frequencies) or away (lower frequencies) from you.

But about finding a speed with a doppler shift on target frequency will be MUCH MORE difficult than to use a simple TMA.

As said compressioncut, to use calculations based on doppler shift will need to double the size of the manual.

Doppler is only used as range finder for distant galaxies, because the expansion factor is already estimated.

[compressioncut]

Doppler effect have an impact depending on the course of the target relative to your position.

the immediate information a doppler shift could give you for a target, is if this target (after beeing identified) is going toward (higher frequencies), perpendicular (normal frequencies) or away (lower frequencies) from you.



And if you know the relationship based on the doppler (Fr vs. Fc vs. F0) you can immediately determine the basic relationship between you and the target, as well as eliminate 180* of its possible courses.

Fr is frequency received, with both platforms' doppler included.

Fc is frequency corrected, with our doppler removed.

F0 is the frequency of interest with no doppler.

Fr < Fc < F0 means we are in an overall opening situation, the target is aft of our beam, we are aft of the target's beam.

Fr=F0, CPA

And so forth.

It doesn't matter much because we can't do anything with it in game.

[Deadeye313]

Jeez, and here I am estimating range by using DEMON to get his speed (FFG Towed array tells you instantly if you know the TPK) and then just lining up the ticks with the lines of bearing. If the ticks are wider apart than the lines of bearing, he's closer, if they are closer, he's further.

I think that's how it works in the game; I've gotten some accuracy on the range and atleast knew where I should have the helo drop the DICASS.

[compressioncut]

Jeez, and here I am estimating range by using DEMON to get his speed (FFG Towed array tells you instantly if you know the TPK) and then just lining up the ticks with the lines of bearing. If the ticks are wider apart than the lines of bearing, he's closer, if they are closer, he's further.

I think that's how it works in the game; I've gotten some accuracy on the range and atleast knew where I should have the helo drop the DICASS.

Oh yeah that'll work, but the likelihood of catching a modern submarine blade signature in real life on an SQR-19 is slim. Even in game with LWAMI I can't say as I've seen one.

As well, there is "bearing jitter" on a real towed array, which means you can't plot the bearings on the strip plot until you have faired (averaged) bearings. That means a number of updates before you can even start, whereas the doppler relationship is immediate.

[Henson]

IRL, we have learned how to do it VERY quickly as submarine encounters have occurred at ever-shrinking ranges.

Coming to PD we'll generally do 3-6 minute legs to clear baffles and get ekelunds on nearby contacts for safety reasons. We try not to proceed to PD without a full baffle clear within the previous XX minutes. It really is a "turn, turn, got it, move on."

[SeaQueen]

the immediate information a doppler shift could give you for a target, is if this target (after beeing identified) is going toward (higher frequencies), perpendicular (normal frequencies) or away (lower frequencies) from you.


That all by itself is useful for TMA purposes. If you looked at your broadband screen and saw his bearing changing over time, while the doppler over time said something else, you could paint a picture much quicker.


But about finding a speed with a doppler shift on target frequency will be MUCH MORE difficult than to use a simple TMA.

As said compressioncut, to use calculations based on doppler shift will need to double the size of the manual.


That's probably true... but the manual is short on calculations anyhow. It really doesn't convey how mathematically intensive naval warfare CAN BE. Calculations are a part of warfare in general, and naval warfare especially. I don't really have a problem with that, though, because that's not what the manual is there for. The manual for the simulator should be enough to get you up and running. That's it. The manual we have does that.

It's up to the ASW geeks like us to write supplements, develop tactics, design scenarios, etc. which will allow the children to learn the real depth of what's provided.

But... unfortunately... we have no useful Doppler effect in DW. :nope:


Doppler is only used as range finder for distant galaxies, because the expansion factor is already estimated.

\/\/hatever...

[Henson]

AS for the doppler questions, IRL we plot Frequency versus Time, just like we do bearing.

Just as the Time/Bearing plot gives us bearing rate, Time/Freq gives us range rate, or rate of closure. We are able to use basic line of sight geometry to take ownship's contribution out of the equation, and that leaves us with the target's speed in the line of sight. That is also minimum speed. The shapes on the plot can do a lot of things, such as tell us what kind of LOS we're in, and track range closed on each leg. We can even calculate course from it.

Once you have a good range and base frequency computed, you will never need anything other than a good Time/Freq plot to continue tracking. It's like magic. Getting to that point is the trick.

[Bill Dickson]

Thanks for all th info which is very informative.

Unfortunatley some of it is over my head as I am fairly new to DW, but I will keep this informstion for use when I can more fully understand it. In the mean time it is back to the manuals and other docs I can find to try to understand how to work sonar and plot taergets.


Once more thanks for all your comments

Bill Dickson