TMA and Bearing Rate question.

[goldorak]

Ok, I've been trying to understand how to use the bearing rate parameter in the navmap ddi with the tma station.
Some things are not clear to me and I hope someone could clarify those issues.


Lets suppose my submarine is stationary and I detect a contact s1 at bearing 45. If over time the bearing rate of s1 is to the left that means s1 course is anything that takes it to the left of the bearing line 45 ?
Is this correct ? :hmm:
And if the bearing rate of s1 is to the right of bearing line 45 than its course can be any value that takes it to the right of the bearing line 45 ?
Do I understand correctly in this case how bearing rate works ? :hmm:

Now, lets suppose my submarine is on a certain course.
I detect s1 and find in the tma station a number of bearing lines that form an x.
So basically without maneuvering I can't determine if I'm on a lag or lead course with the contact.
Can the bearing rate of the contact help me descriminate between lag and lead course without me having to maneuver ? :hmm:
So for instance if I'm on a course of 90 and find that the bearing rate of the contact s1 is towards the left can I surmise that I'm on a lag course with s1 ?
If on the other hand the bearing rate of s1 is towards the right can I surmise that I'm on a lead course with him ?

Any explanation is welcome.

[PeriscopeDepth]

Isn't the bearing rate in the navmap not the actual bearing rate but the bearing rate generated by your solution? Also, the bearing rate in the FFG sonar display seems to be horribly off. When you want an accurate bearing rate you have to do it manually I think.

PD

[goldorak]

I think that once you have a contact s1, when it updates the bearing lines in the tma station (every 2 minutes or so) you automatically get an updated bearing rate in the ddi.
But thats not the problem i have with it.

Please lets not derail this thread, the question and doubts i have are in the first post.
Anyone that can clarify my doubts/errors is welcome to post.

[Henson]

My recommendation (if you're really serious about using bearing rate) is to get an accurate bearing rate by creating a manual time vs. bearing plot on graph paper.

You are correct. The main thing you get from bearing rate is the overall direction of relative motion, ie is he drawing left or right of the line of sight. The problem you run into is lead vs overlead. That will more than likely require a maneuver to figure out...I will say however that if your bearing rate is low and your crossed bearings on the geoplot are relatively far away that you are more than likely looking at an overlead, while a lag will have more of a classic "fan" shape with crossed bearings significantly closer. An experienced eye will tell you that a lag simply 'looks different' from an overlead, but it's difficult to qualify in writing. The reason it's better to maneuver is because maneuvering from a lag to an overlead or vice versa will give you a minimum range on one leg and a maximum range on the other, which really helps your solution lock in nicely after only two, maybe three legs on a non-maneuvering contact.

The added benefit to a manual Time/Bearing Plot, by the way, is that it can tell you if a non-maneuvering target is opening or closing by showing whether the bearing rate is decreasing or increasing respectively. It will also show you Closest Point of Approach, which is at the point of highest bearing rate.

[SeaQueen]

Originally Posted by goldorak

Lets suppose my submarine is stationary and I detect a contact s1 at bearing 45. If over time the bearing rate of s1 is to the left that means s1 course is anything that takes it to the left of the bearing line 45 ?
s this correct ? :hmm:

And if the bearing rate of s1 is to the right of bearing line 45 than its course can be any value that takes it to the right of the bearing line 45 ?
Do I understand correctly in this case how bearing rate works ? :hmm:

Sort of. The bearing rate tells you about RELATIVE motion, so actually, the combination of both yours and his course and speed are such that he's drawing right or left. So you have to imagine everything in a reference frame where your submarine is stationary.

For example, your bearing rate could show a target drawing to port, even if you were on parallel courses, if you were overtaking him and he passed down the port side.

[micky1up]

as a tactical system royal navy submariner i can tell you in the real world of subs all you start off with is bearing rate its the only true piece of information you start off with yes sonar can give you a guesstimate of speed and class of target but bearing rate is all you need to get course speed and range of the target its the baseline of all the work tactical operators use im going to provide a guide to tma for you guys to use i have tried it in the game and it duz work

[Henson]

Originally Posted by micky1up

as a tactical system royal navy submariner i can tell you in the real world of subs all you start off with is bearing rate its the only true piece of information you start off with yes sonar can give you a guesstimate of speed and class of target but bearing rate is all you need to get course speed and range of the target its the baseline of all the work tactical operators use im going to provide a guide to tma for you guys to use i have tried it in the game and it duz work

Wow, you're the closest guy to my job I've found on the forums yet. I'll be interested to see what you put up here. It's funny to me that most people don't realize that sonar doesn't do it all (jonesy syndrome).

You are obviously more motivated than I am.

[goldorak]

Originally Posted by micky1up

as a tactical system royal navy submariner i can tell you in the real world of subs all you start off with is bearing rate its the only true piece of information you start off with yes sonar can give you a guesstimate of speed and class of target but bearing rate is all you need to get course speed and range of the target its the baseline of all the work tactical operators use im going to provide a guide to tma for you guys to use i have tried it in the game and it duz work

If its not classified information, do you want to illustrate how you can guessestimate speed and course of a terget using only bearing rate ?
Maybe use a little example, something easy to understand for non navy people (ie me ).
It would be nice to use such knowledge in dangerous waters.

[Henson]

Originally Posted by goldorak

If its not classified information, do you want to illustrate how you can guessestimate speed and course of a terget using only bearing rate ?
Maybe use a little example, something easy to understand for non navy people (ie me ).
It would be nice to use such knowledge in dangerous waters.

It's all building blocks. Bearing rate over two legs will give you an ekelund range. Range combined with bearing rate will give you course and speed. It all fits together; what makes it hard is that so many of the pieces are missing when you start the problem.

[Wim Libaers]

Originally Posted by PeriscopeDepth

Isn't the bearing rate in the navmap not the actual bearing rate but the bearing rate generated by your solution? Also, the bearing rate in the FFG sonar display seems to be horribly off. When you want an accurate bearing rate you have to do it manually I think.

PD

Correct. The navmap bearing rate is determined by your TMA work.

[PeriscopeDepth]

And that's why it's kind of silly using it for TMA. But there I go not being helpful again...

PD

[micky1up]

am building my post soon so standby for heavy maths work

[PeriscopeDepth]

Awful at math. But that's what programmable calculators are for. Do you happen to have a formula called tri range? A sonar tech posted it awhile back but he has since left the boards. It's a fast way to get range with bearings from sphere and TA.

PD

[goldorak]

Originally Posted by PeriscopeDepth

And that's why it's kind of silly using it for TMA. But there I go not being helpful again...

PD

My apologies, it seems i didn't understand correctly what you were trying to explain.
So the bearing rate indicator in the ddi is only as good as your tma ?
Silly me for thinking the bearing rate was indipendent from the tma solution.

[PeriscopeDepth]

Originally Posted by goldorak

My apologies, it seems i didn't understand correctly what you were trying to explain.
So the bearing rate indicator in the ddi is only as good as your tma ?
Silly me for thinking the bearing rate was indipendent from the tma solution.

Apology accepted . Yes, the bearing rate is only as good as your TMA. I used to think it was the actual bearing rate also until I tried Ekelund ranging and got really weird results. I REALLY REALLY wish Sonalysts would give you the bearing rate of a tracker so you don't have to pull out a stop watch.

PD