Estimate submarine's depth

[Destex]

The most sonar can do is provide an estimation whether the target is above or below the layer. Analyzing accurate depth is not possible.

[Aktungbby]

TYCZYW! A little required reading: https://fas.org/man/dod-101/navy/docs/fun/part09.htm In a nutshell:

Due to the fact that the principals of sound propagation through the water remain physical constants, in some respects ASW of the future will resemble that of World War II. There will be great differences, however, primarily attributed to the vast improvements in submarine and shipboard quieting technologies. Figure ( ) provides a historical perspective on the relative improvements in source levels of U.S. and Russian submarines. It is clear passive sensing of modern submarines is becoming difficult at best. With no control over target source levels and very little control over ambient noise, it becomes incumbent on systems designers and operators to maximize passive detection thresholds and directivity indices, along with continual implementation of self noise level improvements.

Continued emphasis will be placed on development of new sensor types and radical new concepts applied to current technologies. Some examples of innovation on the research and development forefront include:
- Fiber optic towed array: allowing higher data rates, and longer, lighter cables
- Satellite and aircraft based laser detection: Use of the electro-optic spectrum for ASW detection is receiving much attention. Implementation remains in the distant future, however. - Low frequency active towed arrays: With variable length and depth cables and longer range active sonar sources, the tactical disadvantage of active ASW revealing ownship position is reduced.

...and mind your 'Convergance Zone' at all times https://defence.pk/pdf/threads/tactics-101-anti-submarine-warfare-asw.270380/

[shipkiller1]

Originally Posted by jerseytom

If you're underwater in 3d space - target depth and bearing/distance I would think are fundamentally no different to measure - particularly with a spherical sensor array.

On US submarines, ALL bearings are 3D.

Originally Posted by PL_Harpoon

I think it all depends whether your sonar can get a 3d bearing or not.
If yes, then you don't even need to calculate it separately. Just do a simple trigonometry once you know your target's position.
If no, then things get a little bit more complicated.

Incorrect. You forget that sound in water does not travel in a straight line from the source. It bends based on the Sound Velocity Profile (SVP - Temp vs. Depth). It always follows the path of least resistance. This is how Convergence Zones (CZ) are created, for example.

Originally Posted by MBot

Considering how sound propagates in water and that sound waves that are received from the lower hemisphere might still originate from a source above you, shouldn't it be extremely hard to determine target depth?

Your terminology is incorrect. Not hemisphere, but depth. See above.

Originally Posted by Destex

The most sonar can do is provide an estimation whether the target is above or below the layer. Analyzing accurate depth is not possible.

In all actuality, the only way to determine if the noise source is above or below the layer (if there is one) is to see if the noise source has a higher Signal to Noise Ratio (SNR) when you are above the layer then below it. Own ship has to do a depth excursion.... You cannot determine the actual depth. Its really only 'is the contact above or below the layer'. If there is no layer, then you cannot determine what target depth is.

[shipkiller1]

To follow up and clarify this '3D'.

Submarine sonar systems determine not just the bearing (angle in the X axis) of the energy source but also the angle in the Y-axis. This is accomplished by Beam-forming.

You can read about it here in a unclassified PDF.

http://www.dtic.mil/dtic/tr/fulltext/u2/a250189.pdf

[TigerDude]

Originally Posted by shipkiller1

To follow up and clarify this '3D'.

Submarine sonar systems determine not just the bearing (angle in the X axis) of the energy source but also the angle in the Y-axis. This is accomplished by Beam-forming.

You can read about it here in a unclassified PDF.

http://www.dtic.mil/dtic/tr/fulltext/u2/a250189.pdf

This can be done in a spherical array, but not via a hull array or towed array.

No one in the 60s or 80s used vertical angles for anything. All displays were strictly bearing. Vertical info was inferred from layers or operational.

Edit: the earliest spherical array beamforming was done by connecting each transducer to a physical spherical set of contacts with a cap-like receiver that fit over it. You physically maneuvered the cap to where the signal was strongest. The cap was constructed so that the center contacts had a delay on them, with the delay dropping to zero at the edges [I think that's right, but if it isn't then it's the other way], so that what you were doing was finding where the signals matched what a sound wave would do as it passed over the spherical array.

[Capt Jack Harkness]

Originally Posted by TigerDude

This can be done in a spherical array, but not via a hull array or towed array.

No one in the 60s or 80s used vertical angles for anything. All displays were strictly bearing. Vertical info was inferred from layers or operational.

Edit: the earliest spherical array beamforming was done by connecting each transducer to a physical spherical set of contacts with a cap-like receiver that fit over it. You physically maneuvered the cap to where the signal was strongest. The cap was constructed so that the center contacts had a delay on them, with the delay dropping to zero at the edges [I think that's right, but if it isn't then it's the other way], so that what you were doing was finding where the signals matched what a sound wave would do as it passed over the spherical array.

Steering sonar by trackball, basically?

[TigerDude]

Originally Posted by Capt Jack Harkness

Steering sonar by trackball, basically?

yep

[Shadriss]

Originally Posted by TigerDude

No one in the 60s or 80s used vertical angles for anything. All displays were strictly bearing.

Not correct. In the mid 60s, the BQQ-5 series and the BQQ-6 were both developed, both of which had spherical arrays. Early versions of the Q-5 did use a system like you described for it's analog trackers, though it's digital ones were done purely by the system itself. Regardless, both of these systems (or their immediate predecessors, where the tech was developed) were deployed in time for the time frames of this game, and both have decent D/E (depression/elevation) coverage in addition to the 360 degree azimuthal coverage.

[TigerDude]

Originally Posted by Shadriss

Not correct. In the mid 60s, the BQQ-5 series and the BQQ-6 were both developed, both of which had spherical arrays. Early versions of the Q-5 did use a system like you described for it's analog trackers, though it's digital ones were done purely by the system itself. Regardless, both of these systems (or their immediate predecessors, where the tech was developed) were deployed in time for the time frames of this game, and both have decent D/E (depression/elevation) coverage in addition to the 360 degree azimuthal coverage.

Not on the waterfall. This might be used to listen, but is not used in the firing solution.

[shipkiller1]

I'll chime in here as the older guy and used the older systems.

BQQ-5B had two analog broadband trackers. Tracker Alpha and tracker Bravo. They each had an exact mechanical representation of the sphere (they were about 2.5ft diam), called a Compensator. The sonar operators had to clean these two compensators each day. The Q5B also had two digital (non-compensated) trackers, Tracker Charley and tracker Delta.

The beamformer would scan the entire sphere for incoming energy in under 1 second, (I know the actual time.....), and display the result on the display.

You also have an audio cursor, which allows the operator to listen to what ever they want to. This is that sonar by trackball that was mentioned.
An average or better broadband operator can just listen to a contact and give you a good id... merchant, trawler, warship, submarine. Sometimes in seconds. There are other things they can do aurally but I will not get into that here.

[Shadriss]

Originally Posted by shipkiller1

You forget that sound in water does not travel in a straight line from the source. It bends based on the Sound Velocity Profile (SVP - Temp vs. Depth). It always follows the path of least resistance. This is how Convergence Zones (CZ) are created, for example.

To further clarify and assist:

You are also making the assumption that the sound path is not having any interactions with the surface or bottom. Even if they don't, you have no way of knowing where along the path the actual origination point is, since range is always an estimate, no matter how good your solution is. But since, in most cases, all sound is going to have at least one surface/bottom interaction, it becomes impossible to determine depth at all.

There's even more factors involved, but that's the Cliff Notes version.