TMA speed problem

[stalintc]

Hi there :)

I am trying to piece together a few things in my head to help myself with learning accurate TMA.

One of the things that is bothering me somewhat is:

I have located a contact and identified it (Amethyste) DEMON shows that it is moving at 4kts.

I am moving at 7 knots.

I have determined its course and have now changed course so that I am moving on an opposite course moving parrallel to it.

Does this mean now that in my TMA I must plot the speed as 11 knots (OS speed + Target speed = bearing line separation I think) or do I still keep the targets speed in TMA as 4kts?

I have determined that if I plot 4kts into TMA it is about 8nm away and if I plot 11kts it is about 12nm away if thats any help.

I would be most grateful for any help as this is annoying me somewhat and I need to decide which of these two theorys of mine are correct :hmm:

Cheers in advance

[Molon Labe]

Use the target's actual speed.

[stalintc]

Thats brilliant thanks!

So I assume in that case the speed of my vessel has no affect on the speed that those bearing lines move away from each other.

I can now believe the Amethyste to be at about 8nm, which in my mind makes sense as a submarine moving a 4kts might be a bit too tricky to detect at 12nm?

That has helped me out bigtime, I spent nearly an hour head scratching and could'nt decide!

[Molon Labe]

The speed you input is the solution's speed. So no, changing your speed doesn't make the other guy go faster or slower. Well, not usually. :-j

The only way your speed effects TMA is in how it varies the origin of each bearing line over time.

[TopTorp '92]

ship's speed will impact the bearing rate and the range rate. Demon will tell you target's speed for sure. With demon you can nail target range much easier if you don't already have it from the Rapid Localization function from the broadband display.

[stalintc]

Fabulous answer gents :) you have been a great help.

I can get back to my scenario when I get back from work today, thankfully its in peacetime, but I have to avoid contact with French Naval units if possible, so im trying to loop around the submarine whilst keeping a close eye on his movements.

Yes the change in bearing rate is what I meant by the speed difference, I got confused into thinking this affected the TMA solution in the TMA plotter :) thanks for clearing me up on that.

I'm still learning as you can tell :P

Cheers

[Deathblow]

With demon you can nail target range much easier if you don't already have it from the Rapid Localization function from the broadband display.

Really? I didn't know demon could be used for ranging... :hmm: ... how?

[SeaQueen]

Really? I didn't know demon could be used for ranging... :hmm: ... how?

Once you have the speed of your target, you can quickly estimate his course, then reverse direction and have an good indication of his range. Each leg should be about 6-8 minutes.

[TopTorp '92]

Really? I didn't know demon could be used for ranging... :hmm: ... how?

Once you have the speed of your target, you can quickly estimate his course, then reverse direction and have an good indication of his range. Each leg should be about 6-8 minutes.

Sea Queen is on target.
Bearing rate comes from your estimate off the broadband display - is the target drawing left or right? Use this to estimate the target's line of sight (LOS). Speed comes from demon. Use bearing rate to get the target on the right LOS and adjust range to get a stack in the bearing difference dots. When you get a stack you will have estimated target range.

[Fish]

Making a map with two platforms in ME, was a great help for me.
Make both platforms the same side, side 0 for example, now set for "show allied" in options.
Playing the map you are able to assign a tracker and see on the nav map how far or how close your estimate is.
Later you let the other platform make course and speed changes with a search tactic.

[stalintc]

Wow more intriguing information!

I have read your document regarding LOS and TMA, a very good read and helpful to a high degree, thanks for taking the time to write it :)

Cheers

[Deathblow]

Really? I didn't know demon could be used for ranging... :hmm: ... how?

Once you have the speed of your target, you can quickly estimate his course, then reverse direction and have an good indication of his range. Each leg should be about 6-8 minutes.

Sea Queen is on target.
Bearing rate comes from your estimate off the broadband display - is the target drawing left or right? Use this to estimate the target's line of sight (LOS). Speed comes from demon. Use bearing rate to get the target on the right LOS and adjust range to get a stack in the bearing difference dots. When you get a stack you will have estimated target range.

Ohhhhh.. You mean use the Demon to acquire speed and then plug that into the traditional TMA... I thought you meant getting range directly from the Demon database...

[TopTorp '92]

Right. Just insert Demon speed into your TMA solver, estimate a course from the bearing rate (for example, if you're going north and the target is on the left, drawing left, then give the target a lag LOS - always assume a closing situation) and finally adjust range to get a stack on the bearing difference difference display. Essentially you have estimated target range on only one leg of data.

Of course, nowadays, Seawolf has the rapid localization feature that greatly simplifies the process.

Happy hunting!

[stalintc]

Well I can tell you now, I have nailed that Amethyste down to a very close accuracy range and it appears to be patrolling in a 5nm elipse and is consistant. Now in the process of manuvering around it.

This mission has lasted 5hrs 30mins so far. I can hopefully get over into non congo waters soon. Excellent stuff!

Thank you!

[SeaQueen]

Well I can tell you now, I have nailed that Amethyste down to a very close accuracy range and it appears to be patrolling in a 5nm elipse and is consistant. Now in the process of manuvering around it.

This mission has lasted 5hrs 30mins so far. I can hopefully get over into non congo waters soon. Excellent stuff!

Thank you!

The real trick is when you're able to estimate his range from just narrowband. That's a little bit more subtle because you end up estimating his range at some point in the past, and then "time correcting," it to interpolate a bearing and range at some point in the future, which happens to minimize the error. Fabulous stuff, really. That's Ekelund ranging. Then there's Speiss TMA...

You literally could build a career out of figuring out clever ways to more accurately estimate ranges to target at arbitrary times based on bearings only. There's lots of ways to do it, and none of them are really perfect. They tend to depend on assumptions about target motion while you're maneuvering, hence the reason that a target which changes course at random intervals is extrordinarily difficult to determine anything about at all, except that he's there.

This is a real problem when two skilled sub commanders detect each other simulataneously. They both know each other is there, but neither really knows quite where with any degree of certainty.

A guy at work promised to give me honorary dolphins if I could figure out how to do bearings only TMA as well as he could. Faced with the challenge, I had no choice but to defend the honor of physicists...