Calculating position, real course and speed only by hydrophones!

Mittelwaechter · 04-23-09, 07:47 PM

Hi Kubryk,

nice to see you are working on this, you are doing a good job there!

Whenever the angle between first and second bearing is small, add a few minutes and ask for the second bearing again to reduce error probability.

The bearing of the hydrophone operator is a cone. In 20 km distance the bearing covers a width of ~ 350 meters (2r pi /360)
The SH3 map tools are not designed to do these 'hydrohunt' calculations.
Try to center the bearingline in the 350 meter cone.

The best way to calculate the virtual bearing is by dividing the complete distance travelled on coursedirection and add the average.

After third bearing estimate the virtual bearing and try to achieve a big angle for the fourth bearing. You may want to surface and go flank for some minutes. Start immediately and do the calculations while sailing.
Try to come to a full stop before asking for the fourth bearing.
Make sure to follow your U-boats coursepath and try to work the fourth bearing exactly.

I have no idea what's going on, but checking your screenshots the initial contact would have been in ~ 5 km distance - according to your fourth bearing and the resulting real courseline. Your hydro operator is not that bad.

There is allways a difference between the real courseline and the calculated courseline, due to the map tools limitations - but it is small enough to still get a proper target solution. Even the distance is irrelevant as long as you head perpendicular to the courseline.

Try to 'correct' the weapons officers perfect settings and change the AOB for +/-10° - you'll still score a hit. Change the distance - Pythagoras will give you a smile.
The real source of error would be the contact speed. But if you want, you can calculate the speed from the complete travelled distance!
(timestamp the initial contact report...

- or keep on restarting the stopwatch...)

The more you close in to your contact, the more error tolerant your setup.
Well, this all requires an exact 'cross bearing' to get your real contact position.

Have fun!

Edit: your conclusion about same speed is correct (your 8 knots story), but the assumption of a perpendicular course is not consequently correct.

04-23-09, 07:47 PM	#8
Mittelwaechter The Old Man Join Date: Apr 2007 Posts: 1,304 Downloads: 35 Uploads: 0	Hi Kubryk, nice to see you are working on this, you are doing a good job there! Whenever the angle between first and second bearing is small, add a few minutes and ask for the second bearing again to reduce error probability. The bearing of the hydrophone operator is a cone. In 20 km distance the bearing covers a width of ~ 350 meters (2r pi /360) The SH3 map tools are not designed to do these 'hydrohunt' calculations. Try to center the bearingline in the 350 meter cone. The best way to calculate the virtual bearing is by dividing the complete distance travelled on coursedirection and add the average. After third bearing estimate the virtual bearing and try to achieve a big angle for the fourth bearing. You may want to surface and go flank for some minutes. Start immediately and do the calculations while sailing. Try to come to a full stop before asking for the fourth bearing. Make sure to follow your U-boats coursepath and try to work the fourth bearing exactly. I have no idea what's going on, but checking your screenshots the initial contact would have been in ~ 5 km distance - according to your fourth bearing and the resulting real courseline. Your hydro operator is not that bad. There is allways a difference between the real courseline and the calculated courseline, due to the map tools limitations - but it is small enough to still get a proper target solution. Even the distance is irrelevant as long as you head perpendicular to the courseline. Try to 'correct' the weapons officers perfect settings and change the AOB for +/-10° - you'll still score a hit. Change the distance - Pythagoras will give you a smile. The real source of error would be the contact speed. But if you want, you can calculate the speed from the complete travelled distance! (timestamp the initial contact report... - or keep on restarting the stopwatch...) The more you close in to your contact, the more error tolerant your setup. Well, this all requires an exact 'cross bearing' to get your real contact position. Have fun! Edit: your conclusion about same speed is correct (your 8 knots story), but the assumption of a perpendicular course is not consequently correct. __________________ 10 happy wolves rear 90 blinded, ensnared sheep. 90 happy sheep banish the wolves. Arrest the 1% - https://www.youtube.com/watch?v=dQ6hg1oNeGE Last edited by Mittelwaechter; 04-23-09 at 07:58 PM.