Calculating position, real course and speed only by hydrophones!

[Pisces]

Originally Posted by Kubryk

Thanks for your reply! I noticed that small angle difference between bearings is somewhat inconvenient, still I'm worried that target would escape. It happened once, I took two bearings but third one I had to do manually, sonarman no longer could hear him. I will try to make that distance bigger though.

The hydro-man only starts calling out within 20km or so (or was it 25km?). But you can hear upto 34km. That range is 70% bigger, and almost 3 times the area of 20km range. At the bearing where the contact has an AOB of 90 degrees it only halve-way through your hydrophone range. So there is usually plenty of time before you really loose it. Unless it happends to be very near the extreme end of the range. Oh well, can't have everything.

Listening yourselve for the soundbeam-sides where the sounds die out is tricky. You do loose a bit of bearing accuracy that way. But listening for maximum volume at the middle bearing is VERY tricky. Then bigger bearing differences are a must.

Use the smaller bearing difference drawing to estimate how much time there is before it is near 90 degree AOB, or it leaves hydrophone range (if you don't mind catching up to it later). Remember, speed of contact is constant, so any distance it has moved along the course is proportional to time between bearings. Then use halve of the time available as the new interval (but be conservative as it is very crude). Or use the old 3rd bearing as the new 2nd bearing if that 1st new interval has allready past, and double the interval before taking the new 3rd bearing. The 3rd bearing doesn't have to end up at 90 degree AOB. It just a way to not fall behind.

But you must be suffering from information overload now. I'll let you digest it first. And alcohol doesn't help.