Enemy sonar?

[richardphat]

Hello folks i dont know much things about sonar. The only thing i know is the device detect accoustic in the water. But how possible...... dds could detect a sub if a machine is stop and which is in silent mod??? In this case there are no echoes made by the submarine. I dont see the relation between them and yet dds detect them............Like in sh3

[Madox58]

It's part of the problem from the Stock game.
You can't hide on the sea floor and such.
Not realistic, but we are stuck with it.

One thing I have done.
I 'Dumb down' the AI stuff
and JSGME it in for early years.
then remove it later on.

That's a personnal work around that
I'm not totally happy with.
But it works for me at the moment.

[Fincuan]

Active sonar (http://en.wikipedia.org/wiki/Sonar). It doesn't matter if the sub makes noise or not, it is still a huge chunk of metal and can be located with an active sonar. It's a bit like an underwater radar, only that it uses sound pulses instad of electromagnetic waves. An illustration on how it works (http://upload.wikimedia.org/wikipedia/commons/0/07/Sonar_Principle_EN.svg)

[Cheapskate]

In theory that's correct. However it would be quite wrong to assume that a sub would always be detected. Many, many factors would influence detection, not least water temperatures.

Coincidentally, was just looking at: http://www.uboat.net/articles/index.html?article=45

Interesting Eh.? This could be one of the reasons why a prominent U-Boat Commander ( I think it was Erich Topp ) wrote in his memoirs that he seldom, if ever, submerged below 30 meters. If so , I wonder what he did in the Winter?? Maybe he hibernated:88) !

Anyhow, as Privateer says, discussion of this is pretty academic. This sort of stuff isn't modelled in SH3. More's the pity!

[Jeff519]

The cold waters of the North Atlantic offer little in the way of thermal inclines compared to the Pacific however.

[Cheapskate]

Overall, I'm sure your right there, Jeff519 ( and welcome to SH3 forums, BTW :sunny: )

There are many areas in the North Sea and, even worse, the Baltic Sea!!, where a submariner couldn't ever expect any comfort from Thermoclines.

However, U-Boats operated in many areas where these distortion effects would have come into play.

Nowhere near as much as the Pacific though, but I think Thermoclines are modelled in SH4??

[Schwuppes]

yer I think they are... I think you even have the thermometer to show you the drop in temperature.
Gotta try that game out one day, but GWX + OLC Ubermod is just too good at the moment. :up:

[Fincuan]

Nowhere near as much as the Pacific though, but I think Thermoclines are modelled in SH4??

They are, but the modelling is very simple. IIRC it's just a single layer at X depth that will reduce hydrophone or active sonar effectiveness by Y percent.

[Cheapskate]

Don't think U-Boats had thermometers but seem to remember that they could take water samples at various depths, and it was a particular crew member's duty to do this.

So its probably true to say that the existence of Thermoclines wouldn't be unknown to them.

If SHIV's implementation is only rudimentary, it sure beats not having it at all!! Seems that the SHIV engine has some pretty good things going for it. Was looking at Mikhayl's Type II conversion the other day. Must say it looked darned impressive.

Can't wait to see what the Atlantic campaign will be like when it gets ported over in its entirety.:D

[1480]

Here is a wonderful read about sound and how it relates to the ocean:

http://www.fas.org/man/dod-101/navy/docs/fun/part08.htm

"There are many areas in the North Sea and, even worse, the Baltic Sea!!, where a submariner couldn't ever expect any comfort from Thermoclines."

Pg 29 in the U-Boat Commander's Handbook states: "In the Baltic and North Sea, conditions are generally bad for sound locating; in other words, favorable for submarines"

I'll read up a little more from two other sources but I want to say the boot had a way to check temperature during that timeframe. I may be way off but I'll check back in a bit.

[Penelope_Grey]

Water density also plays a part, not all water is the same... also the deeper you go the more interference. The Germans knew deeper was safer... in terms of active sonar matters.

[Cheapskate]

Oh Thanks for that info 1480 :up:

It's always nice to know when you've got things completely ar*e about face.:oops:

My reasoning was that, in shallow waters, the sea temperature would be more constant, giving less chance of Thermoclines existing!

Obviously more to it than that!! Lets know what you come up with.

I'll have to get a copy of the Handbook. Could be living dangerously without it

[1480]

Water density also plays a part, not all water is the same... also the deeper you go the more interference. The Germans knew deeper was safer... in terms of active sonar matters.


Water density is kind of weird once it comes to sound wave conductivity. There are three parts to the equation but it's an important part. The deeper statement goes well in theory to passive sonar as well. And since we all know that SH3 is modeled perfectly :rotfl: then it should work :rotfl: flawlessly. :rotfl:

seriously, you do bring up some great points, I just wished the game was hard coded to take that into account.

[1480]

Oh Thanks for that info 1480 :up:

It's always nice to know when you've got things completely ar*e about face.:oops:

My reasoning was that, in shallow waters, the sea temperature would be more constant, giving less chance of Thermoclines existing!

Obviously more to it than that!! Lets know what you come up with.

I'll have to get a copy of the Handbook. Could be living dangerously without it

Nothing wrong with your reasoning. But like everything else, there are not much in the way of constants anywhere. I found it surprising also when I read it, but since I'm terrible with European geography I had to do research:

North Sea by and by has a lower then average salinity then your normal body of salt water. The Baltic is even lower and is a feeder to the North Sea. There is a pronounced thermal layer for most of the year, found anywhere from 20-50m deep. So a shallow body of water can still support a thermal layer. The weather and circulation also help this make a pretty good hunting ground in the early years of the big one. Happy Hunting Herr Kaleun!

[predavolk]

The Gulf of the St Lawrence had a wicked thermocline coupled with a change in salinity-density that was virtually soundproof. Unfortunately for sub commanders, it was also very difficult to dive through.

[richardphat]

St-Lawrence:hmm: I thought it was St-Laurent?~?~?~?

[Letum]

Water density also plays a part, not all water is the same... also the deeper you go the more interference. The Germans knew deeper was safer... in terms of active sonar matters.

"Water density"?

But water is not compressable; it is always the same density, however high the pressure.

???


Saline density?

[richardphat]

Water density also plays a part, not all water is the same... also the deeper you go the more interference. The Germans knew deeper was safer... in terms of active sonar matters.

"Water density"?

But water is not compressable; it is always the same density, however high the pressure.

???


Saline density?

I thought water density was 1g/ml and the water+salt( usually in sea) is 1,03g/ml. I think he was trying to say the density is not the same for (water+salt) because it depends on the weather and other factor like the concentraion of salt........

[1480]

Water density also plays a part, not all water is the same... also the deeper you go the more interference. The Germans knew deeper was safer... in terms of active sonar matters.

"Water density"?

But water is not compressable; it is always the same density, however high the pressure.

???


Saline density?

"In general density can be changed by changing either the pressure or the temperature. Increasing the pressure will always increase the density of a material. Increasing the temperature generally decreases the density, but there are notable exceptions to this generalisation. For example, the density of water increases between its melting point at 0 °C and 4 °C and similar behaviour is observed in sillicon at low temperatures."

"The density of pure water is a constant at a particular temperature, and does not depend on the size of the sample. That is, it is an intensive property. The density of water varies with temperature and impurities."

"Density is a measure of how much matter takes up a certain amount of volume (space)

When you add salt to water, the salt dissolves into ions. The volume increases a small factor, but the mass increases by a bigger factor. This is because the salt ions are attracted to the water and bind closely to the water molecules themselves.

But since the mass increases faster than the volume increases when you add salt, the density increases.

Salt Water is more dense than regular water because for a certain volume, there is more mass (more stuff) in the salt water than there is in the normal water. "

In the most liberal sense, water has density. Sea water contains solids so it is denser then fresh water. Density of a liquid is measured by specific gravity, with pure (distilled) water as the benchmark to which all other liquids are measured by. The more solids a liquid contains, the denser it is. My wife would agree that I am a lot more dense then water......

So yes, PG is correct when stating there are varying densities (total amount of dissolved solids, temperature and depth) when it comes to water (sea water that is). Other factors come into play, temperature being the biggie. The cooler sea water is the more dense it is. Swimming is a bit easier in sea water then fresh water because the higher density makes us more buoyant.

[1480]

"I thought water density was 1g/ml and the water+salt( usually in sea) is 1,03g/ml. I think he was trying to say the density is not the same for (water+salt) because it depends on the weather and other factor like the concentraion of salt........"

You are correct. A strong, fresh water source, ie rain, river etc, will lower the the density or specific gravity of sea water. It dilutes the concentration of solids. You are adding more volume than mass. That along with temperature (colder is denser) is the reason for thermal layers. I could get a little more detailed but my eyes are getting a bit fuzzy.....

[richardphat]

Owie! First time we are talking about science stuff which finally relates to games and real life!:smug: Im proud of you 1480:up:

[UnderseaLcpl]

I wish they could model the ineffectiveness of asdic at high speeds and after depth-charging in GWX. I fear it's hard-coded though. Sure makes things a lot harder.

[1480]

Owie! First time we are talking about science stuff which finally relates to games and real life!:smug: Im proud of you 1480:up:

Well thanks RP. Science has always been an amateur hobby of mine, would have pursued it academically but I hate advanced mathematics. Just explain the theory to me and I can sort it out in my head. Once you start with V x 7/RS - t2, I get dizzy. But I have to warn you, I'm in the "global warming is a natural event camp!"