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Pisces · 05-12-09, 08:58 AM

I feel too tired right now to expand on it, but here is a tool that can help determine the AOB (and from that course) of a contact by bearings only:

http://www.subsim.com/radioroom/showthread.php?t=147719

You can use it in conjunction with the methods described in here, to get speed and distance:

http://www.subsim.com/radioroom/showthread.php?t=110619

There is also a thread in the SH4 section someone recently stated that figured out the same procedure:

http://www.subsim.com/radioroom/showthread.php?t=151526

This a more systematic approach, and takes some time to work out. It involves no guess work. The solutions provided here by the others also work (probably with quicker visual contact) but with more trial-and-error.

As a very simple solution you could do, just to get close, is to just move perpendicular to the direction of the target (put the sound on your 90 or 270 hydrophone), in the direction the bearing drifts (left or right). Since this is reported as a slow contact (less than 8 knots) you can likely manage to do this submerged. If it was faster (medium or fast merchant) you would probably have to surface and move fast. If you keep adjusting your course a bit towards him until this drift stops (sound stays on the same bearing for a long time) you are infact intercepting him (or aka collision course, so be carefull in the end). So you close the distance as fast as possible and maintain you position forward of him. If he was moving away this would have worked quite different. Meaning you can still adjust your course (almost in the direction of the target) until the bearing stops drifting, but you need to be alot quicker then him. Most likely needing to surface and flank, while regularly diving again to know how the bearing drifts. Also keep in mind then that the drift depends on the compass direction towards him, but the hydrophone direction changes as you turn the boat. The sum of your course and hydrophone bearing must stay constant.

If you just set your course to get the sound on the 90/270 direction only initially (so no course adjustments afterwards) then you actually move more forward of him,while he only does the work in closing the distance. It buys more time and distance ahead of him. The tough part is figuring out when you are on his course line and must stop to prepare for shooting. This would have to rely on making visual contact before then.

05-12-09, 08:58 AM	#7
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,892 Downloads: 300 Uploads: 0	I feel too tired right now to expand on it, but here is a tool that can help determine the AOB (and from that course) of a contact by bearings only: http://www.subsim.com/radioroom/showthread.php?t=147719 You can use it in conjunction with the methods described in here, to get speed and distance: http://www.subsim.com/radioroom/showthread.php?t=110619 There is also a thread in the SH4 section someone recently stated that figured out the same procedure: http://www.subsim.com/radioroom/showthread.php?t=151526 This a more systematic approach, and takes some time to work out. It involves no guess work. The solutions provided here by the others also work (probably with quicker visual contact) but with more trial-and-error. As a very simple solution you could do, just to get close, is to just move perpendicular to the direction of the target (put the sound on your 90 or 270 hydrophone), in the direction the bearing drifts (left or right). Since this is reported as a slow contact (less than 8 knots) you can likely manage to do this submerged. If it was faster (medium or fast merchant) you would probably have to surface and move fast. If you keep adjusting your course a bit towards him until this drift stops (sound stays on the same bearing for a long time) you are infact intercepting him (or aka collision course, so be carefull in the end). So you close the distance as fast as possible and maintain you position forward of him. If he was moving away this would have worked quite different. Meaning you can still adjust your course (almost in the direction of the target) until the bearing stops drifting, but you need to be alot quicker then him. Most likely needing to surface and flank, while regularly diving again to know how the bearing drifts. Also keep in mind then that the drift depends on the compass direction towards him, but the hydrophone direction changes as you turn the boat. The sum of your course and hydrophone bearing must stay constant. If you just set your course to get the sound on the 90/270 direction only initially (so no course adjustments afterwards) then you actually move more forward of him,while he only does the work in closing the distance. It buys more time and distance ahead of him. The tough part is figuring out when you are on his course line and must stop to prepare for shooting. This would have to rely on making visual contact before then. __________________ My site downloads: https://ricojansen.nl/downloads Last edited by Pisces; 05-12-09 at 09:37 AM.