Range prediction, fast fire solution.

[NavyUSA]

Hi commanders,
With the below image, i show you one of a few tables for prediction range during first phase of tma.

This posted image is usable only if relative bearing of target is 75<=B<=85, and ownship and target are along lag los.
For obtain prediction range must be calculated bearing rate after 2 min from first relative bearing B.
Example: if bearing rate is 1.7, you have the 68.23% probability that target is on interval [5.5 , 6.5] nm. But the probability that target is on interval [6 , 8] nm is 95.4% (Gaussian).
This is a great information (statistic) and no a magic solution.
For calculate bearing rate with good accuracy i have find simple method in a manual of tma from betasom forum, in italian language. I haven't had problem understand with google translate.
Last point important, this tables must be used with ownship speed between 6,7 knots, and when target speed is between 5,7 knots. In all other situations the error of prediction will increase.

[Pisces]

Can you explain the rational behind those standard deviation numbers? What sort of probability is that? Also how do you get from probability percentages to standard deviations and back in the first place. (I like math, but I suck at statistics, so it's still magic to me)

While my Italian is even worse than my 'statistic', it would have been nice if you could have provided a link to that forum. Maybe it is public enough to get a peek inside on that method. And let Google Translator have a go at it. Could be fun.

Still, only with relative target bearing between 75 and 85, and speeds between 6 and 7 , or target needing to be between 5 and 7, seems to be quite limiting in use to me. Such narrow bounds.

[NavyUSA]

Originally Posted by Pisces

Can you explain the rational behind those standard deviation numbers? What sort of probability is that? Also how do you get from probability percentages to standard deviations and back in the first place. (I like math, but I suck at statistics, so it's still magic to me)

Speak about the statistical theory in this forum is off-topic. In literature you can find the whole theory.

You know that the bearing rate has a very good correlation with the distance of the contact. It's inversely proportional to the range. These tables are born, from a statistical analysis of Bearing rate variation, by varying the range, route target and relative bearing.

Originally Posted by Pisces

While my Italian is even worse than my 'statistic', it would have been nice if you could have provided a link to that forum. Maybe it is public enough to get a peek inside on that method. And let Google Translator have a go at it. Could be fun.

If Cristian from Betasom, wants personally explain in English this method, would be better. But I think it's very clear. The link below:
http://www.betasom.it/forum/index.php?showtopic=33792
The direct link is this: http://goo.gl/S7iAUy
Page 24.

Originally Posted by Pisces

Still, only with relative target bearing between 75 and 85, and speeds between 6 and 7 , or target needing to be between 5 and 7, seems to be quite limiting in use to me. Such narrow bounds.

For all relative target bearings between 20 and 160 there is a table. I can send you all tables on your e-mail address.
About it, I think that speeds between 5 and 7 knots are not very restrictive, for several reasons.

[Pisces]

Originally Posted by NavyUSA

Speak about the statistical theory in this forum is off-topic. In literature you can find the whole theory.

Well, I didn't mean to ask about what standard deviations are in general. Just in this context, in that table. Standard deviations are the summed squares of differences to a mean value, divided by the population size. But what sort of values and means is that table based on? 'Barnacle size' on the sperical array?

You know that the bearing rate has a very good correlation with the distance of the contact. It's inversely proportional to the range. These tables are born, from a statistical analysis of Bearing rate variation, by varying the range, route target and relative bearing.



If Cristian from Betasom, wants personally explain in English this method, would be better. But I think it's very clear. The link below:
http://www.betasom.it/forum/index.php?showtopic=33792
The direct link is this: http://goo.gl/S7iAUy
Page 24.

Fair enough. I'll see how far I'll get this this document. Looks juicy. Too bad it isn't already in english.

For all relative target bearings between 20 and 160 there is a table. I can send you all tables on your e-mail address.
About it, I think that speeds between 5 and 7 knots are not very restrictive, for several reasons.

Would you care to elaborate on that? Are you expecting all opponents to move at speeds between 5 and 7 knots? Sure, submerged opponents that know that you are there would want to stay silent, and thus slow. But that doesn't account for all,or most situations.

Anyway, I think I'll have pizza tonight and set my teeth in this document. Thanks

[NavyUSA]

Originally Posted by Pisces

Well, I didn't mean to ask about what standard deviations are in general. Just in this context, in that table. Standard deviations are the summed squares of differences to a mean value, divided by the population size. But what sort of values and means is that table based on? 'Barnacle size' on the sperical array?

The population is made by misure of the bearing rate for different target course, range and relative bearing, a large number of measurements.
The standard deviations in that tables shows how much is variation or dispersion of the bearing rate from the average value, for the particular situation fixed by relative bearing, type of los and range.

Originally Posted by Pisces

Would you care to elaborate on that? Are you expecting all opponents to move at speeds between 5 and 7 knots? Sure, submerged opponents that know that you are there would want to stay silent, and thus slow. But that doesn't account for all,or most situations.

Good observation. During a research phase, the submerged opponents probably want to stay silent at speeds between 5 and 7 knots, best search speed is 7.
If a player is moving at speeds less than 5 knots, means that its towed array will be curved in depth, this will not give him a good solution, and the transducers can be below the layer. I think that an experienced player will never move at speeds less to 4 knots in research or attack phase.
Still, if the target has a velocity greater than 8 knots, is very likely that you will hear him with two sensors or you can get information from the demon. In these cases it's easy to proceed with the usual methods, Triangulation, Strip plotting ecc..


I have answered to your doubt?



Thank you for your interest

[NavyUSA]

Pisces, what methods you use to calculate the Br?

I to calculate a history of Br use the method described by Cristian, but if I want to calculate a single value of Br I determine the angle between two lines of bearing directly from the screen of the Tma station (trigonometric).