Interpreting Broadband lines?

johnnyrey · 03-29-19, 03:15 PM

I swear I read/watched something that indicated concave vs convex lines on the broadband display would indicate if a contact was getting closer or further away.

Common sense says concave means a contact is getting closer, and convex further, but can anyone confirm?

Does anyone have info on this, or perhaps know what tutorial I'm talking about?

ET2SN · 03-29-19, 05:09 PM

Just think it through.

If a contact's line is bending towards your heading, you can assume its closing.
If the line is bending away from your heading, you can assume its opening.

I use the word "assume" because the broadband trace only shows the relative bearing of the contact compared to your course and speed. That's why you need TMA. You figure out a rough course, speed, and range then tweak the solution over time to make it fit better.

johnnyrey · 03-31-19, 10:20 AM

Yep, makes sense. Thank you!

ET2SN · 03-31-19, 07:59 PM

Well, try not to concentrate too much on the broadband patterns.

What you're seeing is the contact's bearing and its bearing rate over time.

Low bearing rate (traces that are mostly vertical) usually mean that the contact is distant and/or mostly on the same course as you are. A trace that shows a lot of a curve towards the horizontal means the contact's bearing rate is changing.
This could be due to speed, closer range, CPA, or a maneuver (aka, a Zig). When you see that big bend in your waterfall display, its usually a good time to check your solution to see if its holding up.

Kapitan · 04-01-19, 03:45 PM

I would also look at having a read up on the Red Book and Blue book of submarine tactics, but also a good one is timygoo TMA manual.

All can be found in the download section or at www.subguru.com

p7p8 · 04-01-19, 05:16 PM

Quote:

Originally Posted by johnnyrey

I swear I read/watched something that indicated concave vs convex lines on the broadband display would indicate if a contact was getting closer or further away...

Yeah, I remember something like above in YT video. Currently I cannot find it.
Btw there is much better way to measure this problem without TMA work (which takes some time)
Sound propagation in DW simulates Doppler effect:
- If target is closing, frequency lines are little higher in NB
- if target moves away, frequency lines are little lower in NB

This old video shows Doppler effect in DW (watch from 3:28):

(You should to watch full video for more value informations about sound propagation in DW)

Polak2 · 04-02-19, 07:23 AM

Quote:

Yeah, I remember something like above in YT video. Currently I cannot find it.

I think it is still there included in FPSchazly's DW Tutorials.
Dangerous Waters Tutorial 7: Basic TMA and Sonar Trends

Polak2 · 04-02-19, 07:25 AM

Quote:

Yeah, I remember something like above in YT video. Currently I cannot find it.

I think it is still there included in FPSchazly's DW Tutorials:
Dangerous Waters Tutorial 7: Basic TMA and Sonar Trends

p7p8 · 04-02-19, 07:43 AM

Quote:

Originally Posted by Polak2

I think it is still there included in FPSchazly's DW Tutorials:
Dangerous Waters Tutorial 7: Basic TMA and Sonar Trends

You have right! I've checked tutorial 7 and there is something about it.

I always recommend FPSchazly turorials as very good source of knowledge for beginners

Btw method with doppler effect is also useful when target speed is greater than 8 kts.

03-29-19, 03:15 PM	#1
johnnyrey Swabbie Join Date: Nov 2016 Posts: 13 Downloads: 16 Uploads: 0	Interpreting Broadband lines? I swear I read/watched something that indicated concave vs convex lines on the broadband display would indicate if a contact was getting closer or further away. Common sense says concave means a contact is getting closer, and convex further, but can anyone confirm? Does anyone have info on this, or perhaps know what tutorial I'm talking about?

04-01-19, 03:45 PM	#5
Kapitan Sub Test Pilot Join Date: Mar 2005 Location: UK + Canada Posts: 7,090 Downloads: 68 Uploads: 7	I would also look at having a read up on the Red Book and Blue book of submarine tactics, but also a good one is timygoo TMA manual. All can be found in the download section or at www.subguru.com __________________ DONT FORGET if you like a post to nominate it by using the blue diamond Find out about Museum Ships here: https://www.museumships.us/ Flickr for all my pictures: https://www.flickr.com/photos/131313936@N03/ Navy general board articles: https://www.navygeneralboard.com/author/aegis/

03-29-19, 05:09 PM	#2
ET2SN ET2/SS Join Date: Oct 2017 Posts: 2,505 Downloads: 58 Uploads: 0	Just think it through. If a contact's line is bending towards your heading, you can assume its closing. If the line is bending away from your heading, you can assume its opening. I use the word "assume" because the broadband trace only shows the relative bearing of the contact compared to your course and speed. That's why you need TMA. You figure out a rough course, speed, and range then tweak the solution over time to make it fit better.

03-31-19, 10:20 AM	#3
johnnyrey Swabbie Join Date: Nov 2016 Posts: 13 Downloads: 16 Uploads: 0	Yep, makes sense. Thank you!

03-31-19, 07:59 PM	#4
ET2SN ET2/SS Join Date: Oct 2017 Posts: 2,505 Downloads: 58 Uploads: 0	Well, try not to concentrate too much on the broadband patterns. What you're seeing is the contact's bearing and its bearing rate over time. Low bearing rate (traces that are mostly vertical) usually mean that the contact is distant and/or mostly on the same course as you are. A trace that shows a lot of a curve towards the horizontal means the contact's bearing rate is changing. This could be due to speed, closer range, CPA, or a maneuver (aka, a Zig). When you see that big bend in your waterfall display, its usually a good time to check your solution to see if its holding up.