Calculating contact depth

[tigerfish55]

Hi I would just like some advice on the following question:

If you are playing as a submarine how do you calculate the depth of another submarine that you are tracking? Is the target's depth provided automatically on the nav display and do you have to rely solely on this or can one determine it by themselves using the sonar waterfall display or other techniques etc.? For example if you have set up a trail can you quickly determine whether a submerged contact is getting shallower or going deep or is level.

Many thanks for your help

[sonar732]

The basic way to know a sub's depth is find the SSP. If you have a strong layer and see the sub in BB, then it's in the same layer. However, if you loose it all of the sudden, it has gone to the opposite layer. In the game, you can't tell how deep it is except for this method.

[SeaQueen]

Originally Posted by sonar732

The basic way to know a sub's depth is find the SSP. If you have a strong layer and see the sub in BB, then it's in the same layer. However, if you loose it all of the sudden, it has gone to the opposite layer. In the game, you can't tell how deep it is except for this method.

I wonder if it would be possible to modify the acoustic engine to model near field effects.

[Henson]

One of the basic assumptions made in TMA is that you and the contact of interest are at the same depth.

TMA is a 2 dimensional problem, but weapons employment is three dimensional (ie you can use ceiling and floor for safety).

[tigerfish55]

Many thanks for the replies,

Seems ashame that this is not included in the game - I thought submarine warfare was 3 dimensional. Could the game not be updated to include it in a mod?
Just out of interest does anybody know how they calculate the depth of a target submarine in real life?

Cheers

[OKO]

Henson just told you it is NOT a realistic feature, Tigerfish

to determine a depth, you need a vertical measurment
you could do that if sensors are above from each others.

this is not the case for TA, neither for hull sonars.

But you could argue ... it is the case for sperical !

I won't be really surprised, in fact, if latest sphericals arrays could provide a depth information. Not that accurate, but to give an idea if the contact is under or above OS, measuring the difference on the time upper sensors and down sensors of the sperical will receive the sound track.
As WAA can do horizontally, but in a vertical way.

[Wim Libaers]

A problem with vertical measurements is that the sound is bent by density gradients in the water. So sound from a distant sub below you might reach you from above. This also means that, in a very bad environment with significant sideways density changes, it would not be possible to even get a good bearing in the horizontal plane. Not sure how often that is a problem on real subs.

[SeaQueen]

Originally Posted by OKO

Henson just told you it is NOT a realistic feature, Tigerfish

He didn't say that. He just said that one of the fundamental assumptions of TMA is that the target is at the same depth as the searcher.

There are some tricks that you can use to make an educated estimate of target depth. With some short ranged sonars, transmission loss is accounted for entirely by nearfield effects. By noting how quickly targets fade in and out, and knowing one's own hydrophone depth, one can take advantage of the the near field Lloyd mirror effect to guess at it the target's depth.

There's all kinds of tricks one can use. If one has a good estimate of transmission loss, one can do all kinds of things. Unfortunately, in DW, the way it represents things is too simplistic to do this kind of thing.

It's probably just as well, because to get a good measurement of TL means sitting down with a computer and having it solve a parabolic equation. And you guys think me playing the game with a spreadsheet ready is intense! HA!

[Henson]

Yeah, some clarification is in order.

When we have to make an assumption about depth we use our knowledge of the type of contact we are tracking and the operations he is doing to put us in the ballpark. We generally don't know depth until the torpedo sends that data back to us. That is not always the case, but it is a good percentage of the time.

The good news is that we don't NEED depth for TMA. TMA falls under what FT's call SWAG (Sophisticated Wild-*ssed Guess). We make a lot of assumptions just to make the math manageable, such as:

Both contacts are at the same depth.
O/S maneuvers are intantaneous.
The ocean floor is perfectly flat.

This gets us "close enough," which in undersea warfare is really all you need. This isn't like WWII where you're shooting on gnats-*ss short range corrected intercepts; our goal here is to use relative motion to stay safe (ie is he far enough away from us that we're in our comfort zone), as well as to use the employment of 'advanced corrected intercept' tactics (which ask the question, "Can my weapon find him?") As weapons get better, solutions become less important (though a good solution will always be a vital fundamental).

In short, we don't need to know his depth. There are times when we will use his expected depth BAND to help our tactical situation (ie if you're shooting at a sub that is not at PD in a high contact density area, set a low ceiling for your weapon), but for TMA itself depth isn't much of a concern.

Could a more accurate bottom depth and contact depth help us with DE and bottom-bounce ranges? YES, but it's a difference that is small enough not to worry about. 4,752 yds is still 2.5 miles...close enough.

Remember what my old chief used to tell me guys, "close enough for the girls we go out with."

[TLAM Strike]

Originally Posted by tigerfish55

Just out of interest does anybody know how they calculate the depth of a target submarine in real life?

Cheers

Older subs had four hydrophones on the sail. They measure the signal strength on the four hydrophones to find if the target is above or below and to port or starboard.

Newer subs have their computers determine the contact’s depth using the sphere array

[Rip]

Originally Posted by Henson

Yeah, some clarification is in order.

When we have to make an assumption about depth we use our knowledge of the type of contact we are tracking and the operations he is doing to put us in the ballpark. We generally don't know depth until the torpedo sends that data back to us. That is not always the case, but it is a good percentage of the time.

The good news is that we don't NEED depth for TMA. TMA falls under what FT's call SWAG (Sophisticated Wild-*ssed Guess). We make a lot of assumptions just to make the math manageable, such as:

Both contacts are at the same depth.
O/S maneuvers are intantaneous.
The ocean floor is perfectly flat.

This gets us "close enough," which in undersea warfare is really all you need. This isn't like WWII where you're shooting on gnats-*ss short range corrected intercepts; our goal here is to use relative motion to stay safe (ie is he far enough away from us that we're in our comfort zone), as well as to use the employment of 'advanced corrected intercept' tactics (which ask the question, "Can my weapon find him?") As weapons get better, solutions become less important (though a good solution will always be a vital fundamental).

In short, we don't need to know his depth. There are times when we will use his expected depth BAND to help our tactical situation (ie if you're shooting at a sub that is not at PD in a high contact density area, set a low ceiling for your weapon), but for TMA itself depth isn't much of a concern.

Could a more accurate bottom depth and contact depth help us with DE and bottom-bounce ranges? YES, but it's a difference that is small enough not to worry about. 4,752 yds is still 2.5 miles...close enough.

Remember what my old chief used to tell me guys, "close enough for the girls we go out with."

Very true. I can think of several situations we drilled on where you would do 2 quick legs to get an Eklund range and shoot. There is always time to adjust for a refined solution as the weapon gets closer and he begins evasion which almost always means he will head deep.