TMA and range determination

Troels K · Joined: 16 Apr 2005 Posts: 3 Location: Denmark

Hi

I’m new to Dangerous waters.

I’m having some difficulties determining the correct range to a contact. Damn

At the moment I’m using active sonar to find the range. However, it would be nice if the range could be found without active sonar.

Therefore, how do you guys determine a suitable range to a possible target?

I know the basic TMA like lead/lag course, but the manual says that two or tree legs will result in a single possible solution (page 5-22), these two or tree maneuvers confuses me. Confused

This is probably a huge subject, however, some short guidelines would also be appreciated. Thumbs Up

Thanks in advance.

Troels

MaHuJa · Posted: Tue Apr 18, 2006 3:18 pm Post subject:

The easy way out, is to use the autotma. Given enough time, it'll give you a dead-on solution.

Manually, things are a bit more complicated. But all in all, the extra legs are pretty much a requirement. It's a bit hard to explain, at least without illustrations, but there is a saying of sorts; that a change in bearing rate is needed for a good solution. By changing your own course or speed, you're forcing that bearing rate change. The more radical the change, the better.

Personally, I only exceptionally start working on a solution before well into a second leg.

Sonoboy · Joined: 31 Aug 2005 Posts: 59

If you can, assign trackers to that contact on both the towed and spherical arrays. Then, in TMA, where the two different lines converge is a good approximation on the range of the contact.

Troels K · Joined: 16 Apr 2005 Posts: 3 Location: Denmark

Thanks for the replies Thumbs Up

MaHuJa:
The thing I don’t get is, how do I use a change in bearing rate to estimate the range? Rolling Eyes

Sonoboy:
Good advise I will try that. Smile

Troels.

Henson · Joined: 22 Feb 2006 Posts: 35

If you understand the difference between overlead and lead lines of sight, turning from an overlead to a lag or vice verse will provide you with both a minimum and maximum range.

Henson · Joined: 22 Feb 2006 Posts: 35

SKeeM · Joined: 08 Nov 2005 Posts: 45 Location: Bronx, NY

Molon Labe · Posted: Wed Apr 19, 2006 7:25 pm Post subject:

Troels K · Joined: 16 Apr 2005 Posts: 3 Location: Denmark

Once again, thanks for the replies, my TMA has improved significantly. Wink

Henson · Joined: 22 Feb 2006 Posts: 35

Google Ekelund range. You can find this on the internet, but you'll have to dig.

Considering where I got this formula I'm still not comfortable with repeating it in an internet forum, but that seemed a good compromise. There a re a few technical papers that wil take you through the process. It basically uses bearing rate and a change in the line of sight to determine a best estimate of range.

OKO · Posted: Fri Apr 21, 2006 7:18 am Post subject:

Wim Libaers · Joined: 21 Sep 2001 Posts: 396 Location: Flanders

It would have been convenient to have a (time corrected) Ekelund or Spiess line calculator integrated into the TMA screen. You can do it now, but you need some extra tools (writing down bearings and rates often, programmable calculator), while all the necessary information is already in the TMA screen.

SeaQueen · Joined: 23 Jun 2005 Posts: 358 Location: Washington, DC

MaHuJa · Posted: Sun Apr 23, 2006 3:28 pm Post subject:

Getting the bearing rates in the sonar stations on the subs alone would help a lot there.

Anyway, the thing I said applies for general solutions as well - it's through the effect the second leg has that you can vastly reduce the number of solutions.

sonar732 · Joined: 03 Jul 2003 Posts: 1358

I can still remember ultilizing the "wheel" for basic TMA while in sonar A school. Wink

Place data #1 in outside wheel...turn for data #2....mmmm...Look at your crude drawing of LOS...