SUBSIM Radio Room Forums - View Single Post - 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.

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.