Good technique for tracking escort targets -- SONAR Only -- No Map Updates

J.E. McKellar · 06-09-13, 09:03 AM

Lurker piping up here-

I've tried this once or twice, with not much luck, forgot to imput the bearings into the TDC.

I started off with a long-range visual contact, so I knew the basic position and course of the target, and the layout of the convoy. I picked out the light cruiser in the middle to track, because it was easier to isolate her screws from the others. Every three minutes, I would find the bearing from passive sonar and use it to draw a line from my sub's current position. After several measurements, I had several lines radiating out from my slowly moving sub.

Assuming that the target is moving at a constant speed and course, the target's course should intersect those radiating bearings at constant intervals, i.e. the distance from bearing 1 to bearing 2 is the same as the distance from bearing 2 to bearing 3. So I just eyeballed a line running across the bearings that seemed to match pretty well, and then used the compass to double-check and adjust the line.

Now that I had the course figured out, a new bearing reading would give me the distance and AOB, and measuring how far the target traveled over those 3-minute intervals would give me the speed.

After that, you just have to work as a sort of manual TDC, taking more bearings at finer time intervals to make sure all your numbers make sense, and that the target isn't doing anything unusual. Even then, a quick check with the periscope right before firing is necessary to get a precise fix.

Sailor Steve · 06-09-13, 09:07 AM

WELCOME ABOARD!

I like your method. Unfortunately I have problems with calculations beyond 1+1, but your description is easily understood. Thanks for putting it up.

Quote:

Originally Posted by J.E. McKellar

Even then, a quick check with the periscope right before firing is necessary to get a precise fix.

That's always the crux of the problem. You can't be precise with sound only. You always need to look.

in_vino_vomitus · 06-09-13, 10:15 AM

The thing about sonar, is that it's going to pick up the target a long time before anything else, even when your boat is equipped with radar, so you can begin gathering data on your target long before you pick it up by other means. hydrophone data is less accurate than radar, but it's plenty accurate enough to begin manoeuvring long before the target's in visual range. It's highly labour intensive though. By the time I actually see a target I'll probably have three or four moderately different solutions for course and speed. But it means that when I make visual contact I'm at the point of putting the final touches to a firing solution, rather than just starting out. Sometimes I can have a course and speed roughed out from hydrophone data before I pick them up on radar.

As I say, it's labour intensive and I'm lazy. A lot of the time, once I get radar to play with I forget about the hydrophones, but in the early days, when radar isn't an option, the difference they make is huge...

06-09-13, 10:15 AM	#3
in_vino_vomitus XO Join Date: Jul 2009 Location: Preston, Lancs, UK Posts: 418 Downloads: 137 Uploads: 0	Sonar only The thing about sonar, is that it's going to pick up the target a long time before anything else, even when your boat is equipped with radar, so you can begin gathering data on your target long before you pick it up by other means. hydrophone data is less accurate than radar, but it's plenty accurate enough to begin manoeuvring long before the target's in visual range. It's highly labour intensive though. By the time I actually see a target I'll probably have three or four moderately different solutions for course and speed. But it means that when I make visual contact I'm at the point of putting the final touches to a firing solution, rather than just starting out. Sometimes I can have a course and speed roughed out from hydrophone data before I pick them up on radar. As I say, it's labour intensive and I'm lazy. A lot of the time, once I get radar to play with I forget about the hydrophones, but in the early days, when radar isn't an option, the difference they make is huge... __________________ Forget death - I'll take dishonour! [SIGPIC][/SIGPIC] TMO 2.5 1.5 Optical Targeting Correction 031312 for TMO 2.5 1.5 OTC Realistic Scopes for TMO TheDarkWraith_DC_Water_Disturbance_v2_0_SH4 Improved Stock environment v3_TMO&RFB TMO_Alt_engine-sounds TMO_Alternate_JS_Radar_performance TMO17_19_different_smoke Last edited by in_vino_vomitus; 06-09-13 at 11:51 AM.

06-09-13, 09:03 AM	#1
J.E. McKellar Nub Join Date: Jun 2012 Posts: 3 Downloads: 12 Uploads: 0	Lurker piping up here- I've tried this once or twice, with not much luck, forgot to imput the bearings into the TDC. I started off with a long-range visual contact, so I knew the basic position and course of the target, and the layout of the convoy. I picked out the light cruiser in the middle to track, because it was easier to isolate her screws from the others. Every three minutes, I would find the bearing from passive sonar and use it to draw a line from my sub's current position. After several measurements, I had several lines radiating out from my slowly moving sub. Assuming that the target is moving at a constant speed and course, the target's course should intersect those radiating bearings at constant intervals, i.e. the distance from bearing 1 to bearing 2 is the same as the distance from bearing 2 to bearing 3. So I just eyeballed a line running across the bearings that seemed to match pretty well, and then used the compass to double-check and adjust the line. Now that I had the course figured out, a new bearing reading would give me the distance and AOB, and measuring how far the target traveled over those 3-minute intervals would give me the speed. After that, you just have to work as a sort of manual TDC, taking more bearings at finer time intervals to make sure all your numbers make sense, and that the target isn't doing anything unusual. Even then, a quick check with the periscope right before firing is necessary to get a precise fix.