Once a submarine passively detects a contact and develops a TMA solution, what sort of information is obtained?

 

If a "Good" Solution is obtained, does the submarine know course, speed and range to the target?

 

What about "Fair" and "Poor" solutions? This becomes important when firing torpedoes with limited range and enable points ect.

 

Thanks

Once a submarine passively detects a contact and develops a TMA solution, what sort of information is obtained? If a "Good" Solution is obtained, does the submarine know course, speed and range to the target? What about "Fair" and "Poor" solutions? This becomes important when firing torpedoes with limited range and enable points ect. Thanks

 

A useful backgrounder from the Tactics 101: ASW - Part 3 article:

 

Target Motion Analysis (TMA)

 

An initial passive sonar contact typically provides only a bearing to the target, and tells you nothing about distance (range) or speed. The contact may be close by, creeping along at only 5 kt, or twice as distant, and moving at 10 kt.

 

Using only passive sonar, target motion analysis (TMA) is a mathematical process by which a contact's course and range can be estimated using timed readings of the contact bearing and an estimate of its speed. Each estimate is (hopefully) more accurate than the one previous, and eventually the estimation will be accurate enough to reliably predict the next bearing. TMA is thus, essentially, an initial approximation of target range, course, and speed. The closer the ensuing predictions come to reality, the more likely it is that the approximation is an accurate one.

 

Suffice to say, any target whose bearing is changing rapidly is quite close and needs to be localised in a hurry. Conversely, a distant target will show almost no change in bearing over time. (The same can be said, of course, for target that is exactly parallel, but its bearing will change as you change course even slightly).

 

TMA is a tedious procedure, one that can consume a lot of time and create considerable frustration, but it is certainly more stealthy than energizing an active sonar and can eventually produce a suitable firing solution. Initially, TMA calculations involved only a paper plot, used to determine short range fire control, and later evolving into a computerised system using software target tracking that can project a target's position ahead in time and be sufficently accurate to control wire guided weapons.

 

Limitations to the TMA technique include: contact must be maintained over a period of time; all contact bearings must be assumed to come from the same target over that period of time; and maneuvers must be built into own ship track in order to resolve ambiguities.

 

Beyond a certain range, of course, passive TMA techniques cannot reliably produce an accurate solution. For example, for convergence zone (CZ) detections, the only data typically available from passive sonar is a bearing. Range, course, and speed are practically impossible to determine. And, since a CZ contact is easily lost, the TMA solution clock would have to be reset and a new solution started from scratch each time.

 

I'll have to look up the H4 rules to offer its particular perspective.

I suppose, having looked at Rule 6.1.2, it wasn't really necessary to consult them to answer your questions.

 

Once a submarine passively detects a contact and develops a TMA solution, what sort of information is obtained? If a "Good" Solution is obtained, does the submarine know course, speed and range to the target? What about "Fair" and "Poor" solutions? This becomes important when firing torpedoes with limited range and enable points ect.

 

The whole point of TMA is to obtain a reliable estimate of the contact's course, speed, and range. You are trying to achieve all three.

 

Whether the solution (all those things together) is 'Good, 'Fair', or 'Poor' is a matter of degree, being a reflection of the quality of your estimate.

 

As you've noted already, the quality of the solution will impact the hit probability of your torpedoes or ASW standoff missiles.

Thanks. Perhaps I phrased the question wrong

 

I want to know if lets say a "Good" TMA solution is obtained on the first roll that the contact is detected: a 01!! the target is at 18 nm distance. Beyond the range of the submarine torpedoes. I am playing a refereed game. Does the ref tell me that the target is at 15nm? Does he tell me the course and speed of the contact?

 

After all, it is a "Good" solution. I should know with a "Good" solution if my torpedoes will even reach the target.

 

 

I think there should be some flexibility on what information is given players. Maybe a "Good" Solution gives range within +/- 1nm. Course and the speed within 1 or 2 knots.

 

Conversely, a "Poor" solution should give the range within +/- 6nm and the speed within +/- 6 knots ect.....

 

What do you think?

 

thanks

I think there should be some flexibility on what information is given players. Maybe a "Good" Solution gives range within +/- 1nm. Course and the speed within 1 or 2 knots. Conversely, a "Poor" solution should give the range within +/- 6nm and the speed within +/- 6 knots ect..... What do you think? thanks

 

This has been my experience. A 'Good' solution is going to give you pretty accurate info, plus or minus a little. The longer you have a 'Good' solution, the better that info should get.

I think there should be some flexibility on what information is given players. Maybe a "Good" Solution gives range within +/- 1nm. Course and the speed within 1 or 2 knots. Conversely, a "Poor" solution should give the range within +/- 6nm and the speed within +/- 6 knots ect..... What do you think? thanks

 

This has been my experience. A 'Good' solution is going to give you pretty accurate info, plus or minus a little. The longer you have a 'Good' solution, the better that info should get.

 

Ahh. So that makes sense, if you wait, and have a Good Soltn for two or more turns you get more accurate info.

 

Sounds good.

The following was posted by 'someone' on 'another' Harpoon forum (not sure on either).

 

BOL: Well bearing only....

 

Poor: (rough idea on range and speed)

Very close (<1 nm) or Medium (1-9.9 nm) or Far Away (>10 nm) - makes sense, how much noise are they putting in the water?

Target Speed < 15 kts (Y or N) - is the bearing rate changing a lot? SLow or Fast

"Conn, sonar we have a Slow, Medium range contact at 45 degrees"

 

 

Fair:

Target is < 2nm or CZ (I'm not too sure on these two)

Opening or Closing?

Rough course: N, NW, S, etc (this is basically answers opening or closing)

If ship/sub class is known (see sonar classification) target speed say - Slow (1-10 kts), Medium (11-20 kts), Fast (20+ kts)

"Conn, sonar we have a Slow, Medium range contact at 45 degrees, course is opening to the North. Sounds like a Victor III"

 

Good:

Contact range, course and speed

"Conn, sonar. The Victor III is at 12000 yards, bearing 45. Sounds like 120 degrees at 10 knots"

 

 

I've notice in Harpoon PBEM that players do not keep a plot due to time, lack of preparation or laziness. If they are given just bearings and a fire control solution they will stuff up the intercept up.

 

Giving them some kind of information above takes them out of the sonar shack and back into the command chair.

The following was posted by 'someone' on 'another' Harpoon forum (not sure on either).

 

BOL: Well bearing only....

 

Poor: (rough idea on range and speed)

Very close (<1 nm) or Medium (1-9.9 nm) or Far Away (>10 nm) - makes sense, how much noise are they putting in the water?

Target Speed < 15 kts (Y or N) - is the bearing rate changing a lot? SLow or Fast

"Conn, sonar we have a Slow, Medium range contact at 45 degrees"

 

 

Fair:

Target is < 2nm or CZ (I'm not too sure on these two)

Opening or Closing?

Rough course: N, NW, S, etc (this is basically answers opening or closing)

If ship/sub class is known (see sonar classification) target speed say - Slow (1-10 kts), Medium (11-20 kts), Fast (20+ kts)

"Conn, sonar we have a Slow, Medium range contact at 45 degrees, course is opening to the North. Sounds like a Victor III"

 

Good:

Contact range, course and speed

"Conn, sonar. The Victor III is at 12000 yards, bearing 45. Sounds like 120 degrees at 10 knots"

 

 

I've notice in Harpoon PBEM that players do not keep a plot due to time, lack of preparation or laziness. If they are given just bearings and a fire control solution they will stuff up the intercept up.

 

Giving them some kind of information above takes them out of the sonar shack and back into the command chair.

 

Yes! This is the info I was looking for.