Using TA+hull sonar for triangulation
 

Hey again,

I've been playing with the 688(i) again and just had a very strange experience vis-a-vis triangulation using two arrays. I picked up a Han class sub pretty strongly on my towed array (3 frequency lines) and so I thought I might look at my other two arrays to see if I could get him on either. Sphere was blank in NB, but I had a line in the lower window in BB. Unfortunately, DW wouldn't let me mark that line no matter how many times I clicked the designate button on and around its bearing. I then looked on hull NB and bingo, I had the second frequency line coming in feintly. I designated it and merged the contacts in TMA.

Here's where it started to get weird. After a few LOBs appeared, I tried to use the bearing cross from the two arrays to triangulate the target, but the solution I got using the crosspoints was vastly different from what my solution using DEMON said it sould be. I made a new TMA leg, waited for more bearings and again, the triangulation was way off from the solution I got by using just the TA and DEMON.

I got to what I thought was in range and fired two fish, but they didn't seem to lock onto anything and eventually ran out of gas. I was frustrated, so I quit the scenario and viewed the replay and you know what I found? The target was actually way further out than my triangulation suggested. He was at around the exact position my solution using just the TA and DEMON had given me, but I'd thought that the triangulated solution would be more accurate.

Any ideas why this happened? I seem to remember having luck with triangulation before, but I think that was most commonly using the sphere and TA, not the hull. Does the hull array give somewhat inaccurate bearings? Also, why was I able to see an intermediate timescale contact on sphere BB, but was unable to mark it for the life of me?

I'm an idiot in making TMA solution but as far as I know the precise triangulation you mentioned is no longer applicable in DW and it's more realistic that way.

In the previous title like Sub command you will get a perfect precise triangulation when you have a contact tracked with two or more sonar arrays.

I'm not sure as to the exact why but my guess is that for one the different positions of the sonar arrays it self would render perfect triangulation almost impossible. And another that sound doesn't travel in a straight line underwater so you are bound to have bearing differences that would make perfect triangulation almost impossible.

TMA is not a science to me but a kind of an art :damn:. That's another way of saying a thoughtful guessing.

Triangulation with the TA isn't nearly as good as triangulation you get with a UUV because the lines are almost parallel. A very small bearing error can lead to a significant change in range on the solution. Does that mean it's worthless? No, far from it. At times it can be quite accurate. But if you have something better to go on (like a solid unambiguous solution with a known contact speed), go with that.

Something else to keep in mind is that the first bearing lines for new contacts/sensors will be off a little because they aren't on the 2-minute interval so that is going to throw a triangulation off, and obviously there is also the issue where the TA bearing gets thrown off during turns.

I do not know how big the bearing inaccuracies are for each sensor. But you can make best use of it if you beam the contact, and stream the towed array as far as possible.Then the bearings of the 2 sensors are as far apart as possible. If you happend to have your bow and tail line pointed towards or away from the contact then triangulation is useless on it. Then there is no seperation from the contacts point of view.

the problem with use of maximum scope, is, in shallow waters, you'll be dragging your TA, running deaf, and forced to operate at higher speeds to compensate for the drag. Under those conditions, you'll be compromising yourself if you want maximum scope. It's best to optimize maximum scope vs speed based on your environment..

Yes, you need maximum separation between sensors. Next you must proceed with a minimum speed of 7 knots so as to have the towed array in line with ownship. The bigger the depth difference is between ownship and the towed array the bigger the error in the tma solution.
Last but not least, to get a precise triangulation mark the contact on the towed array and hull or sphere sonar AT THE SAME TIME whenever possibile.
This single rule will simply your solution as you can't even imagine.

Edit : when using triangulation 6 minutes (4 minutes to wait for the first couple of bearing lines + 2 minutes for the second couple of bearings line) is all you need to fix a solution. No need to go into several legs, one is more than sufficient if the contact isn't maneouvering.

No, even if you extend the towed array to its maximum length, a speed of 7 knots is sufficient to have the towed array in line with ownship.
No problem of having it drag over the ocean floor.
Go less than 7 knots and yes in shallow waters you'll find the towed array being dragged all over the place.
And frankly the tactical speeds of the 688/seawolf/virginia are quite high that going at 7 knots is no problem at all to search for enemy subs.

The much I remember, what you call "triangulation" was called "master contact". :)

I would rather use the word "triangulation" in a 2 vs 1 situation where the bearings of the hunters are shared to narrow down the exact opponent's position...

That said, TMA has in my opinion rightfully the status of "art of TMA", even more than the "art of evasion" (the last one is an art to me only I think).

I once was good at it, but it is so complex and involves so many decisions that you need constant practicing to keep effective in manual TMA. In a contacts rich environment where your classification quality is poor, this is nearly a job for a professionals (to me).

I dont know if you play online or vs AI, but what I can say is that well done TMA goes far behind than the simple determination of the contact's position... rather it allows to feel the pulse of your prey, and in some games I had the impression I could read my opponent's mind... yes really :)

On the other hand, even here, you'll probably not be able to advance much without a good teacher, as it is plainly too difficult to figure all thing out by yourself (except you have a background already). Best would be a teacher "on the field", practical exercises...

On a final note, i SUSPECT 688 i H/K, SC, DW, and the tons of mods, every single installation will behave differently in nearly everything needing a study by itself (that's what finally pissed me off :))

Another thing that just came to mind.

"Tactical speed": my understanding of this term is, the maximum speed allowed before your arrays start to "wash out(?)", meaning the water flowing on the surface of your sub starts disturbing your sonars, adding noise.

When tracking, it is a good thing to stay at "tactical speed", as you'll get more accurate TMA results, being the lines more distant... meaning the absolute error plays a less relevant role...

NFunky, you pose good questions as I can see from some days now...

Reading them, brought me 5-6 years behind.

I looked into my harddisk and found some documentation from back then. I was a member of the Seawolves without command functions, what I did really like was the battles :arrgh!:

Looking back at the documentation, those were fantastic times. We even had some real submariners, even active submarine officers around...

People i remember are Fish (sort of guru), and many others that I don't read in this forum.

I can say that I was lucky in picking an excellent virtual navy back then (Seawolves), it had the complete hierarchy of a navy. Actually head people were rare or nearly unpossible to talk with heheheh, very resembling after all...

If you haven't considered before, you might want to do some "research" on what is around now as virtual navies, it might become some great experience :yep:

I am not really off-topic, because if you want to understand TMA well, and if you're lucky to find some good instructor/instruction around (for example in a virtual navy), this will boost your skill with much less effort (IMHO).

To tell you one (no joke) I was instructed on Sub Command TMA by a real, active, submarine TMA Officer. Very rarely the questions were so detailed to need an answer like "we're going into classified stuff".
Then it's up to the student to adsorb as much as possible, but you seem to have the requisites to me, as you pose the right questions.


I am unable to make any sort of judgement on the virtual navies around now, but I know some people here are members of the one or the other :DL

yessir, this has always been the context that I've used the phrase :salute:

although I prefer akula 2 imp, tactical speed(in this context) is one of the more aggressive, yet flexible features I've always been fond of on the 688.

I'd say she has this very edge over the rest of the submarines in DW; nothing else out there can provide what she has to offer...

*steps out of cryo tube* :salute:
No DW2 yet? :cry:



If this inaccurate solution was due to bearing error, I would expect that you would have some crossover points further and closer than the target's actual position. Assuming that both arrays were indeed tracking the same target, I do not know how to explain this predicament. I will have to try triangulation with hull and towed arrays for myself.

get DWX it's the long awaited RA mod in its final glorious form!:D
Make sure to apply the patch too

Still very frustrated with how I can see a contact on the sphere broadband but can't mark it until it becomes pretty bright. This has been causing me grief in high contact environments where all four of my TA trackers are being used and I want to track some of the louder (i.e. surface) contacts with sphere. I suppose I could use the hull array for these, but its got such a low washout speed that I'd really rather not.

Anyway, back to using LwAmi 3.09. DWX, while very cool, still has far too many bugs. I don't need more unknowns (bugs) added to the equation in a game where guessing is the primary task.

Nfunky you're going the wrong route with this.
Surface contacts are generally tracked by periscope. It gives you bearing, and distance information through the stadimeter station so 2 measurements are all you need for getting a tma. Speed in this case is irrelevant since it is desumed from the 2 positions you marked.
Let your TA trackers track sub contacts, using those for suface contacts such as merchant vessels is a waste.
You spend time for tma whereas with 2 bearings in persicope + stadimeter gives you a full solution.