The Bearing Rate Course Finding method

Nisgeis · 08-26-10, 06:09 AM

First, apologies if this has been discussed before, I don't recall ever seeing it, but who knows.

Right, so, we know about TMA, where you take a bearing reading at a fixed time interval, but what happens if we take a time reading at a fixed bearing interval?

When thinking about turning so your bow was on the target in order to determine whether the AoB was port or starbaord, I wondered whether that's the point at which when the highest bearing rate change would occur and quickly decided it wasn't, as exactly like the doppler effect and a siren, the sound is at the highest pitch when the siren is closest to you. In that way, the pitch of the siren can tell you when the siren is closest (if the pitch doesn't drop then the siren will collide with you).

When stationary and tracking a target, the point it will be closest to you will be when the target's AoB is 90 (port or starboard) as that is the point at which its position on the track is the closest to your position.

So, now we know that, we can measure and record the time it takes for the bearing to change a fixed interval (say five degrees) and then use that to determine whether target's bearing rate has decreased, which means that the target has passes an AoB of 90. When we have the relative bearing at which the target's AoB was 90 (within a maximum error of two and a half degrees), we can then use our own course to determine tha target's course.

When we have the target's course we can the match that course and use speed matching to hold the target on a constant bearing to determine the target's speed.

So there you have it, a simple method that needs no plotting and no range finding in order to determine target course and speed. It will work for sonar bearings, but to speed match you will need to have an optical bearing if the target is travelling faster than seven knots. If you have radar, this will also work, but you might as well plot.

The disadvantage to this method is that you will always have to surrender a position ahead in order to determine when you are behind the target's beam, but you shouldn't be too far behind and if you aren't fast enough to catch, then you won't intercept.

Anyone see any holes? Apart from not being able to determine range?

08-26-10, 06:09 AM	#1
Nisgeis Ocean Warrior Join Date: Jan 2008 Posts: 2,909 Downloads: 77 Uploads: 11	The Bearing Rate Course Finding method First, apologies if this has been discussed before, I don't recall ever seeing it, but who knows. Right, so, we know about TMA, where you take a bearing reading at a fixed time interval, but what happens if we take a time reading at a fixed bearing interval? When thinking about turning so your bow was on the target in order to determine whether the AoB was port or starbaord, I wondered whether that's the point at which when the highest bearing rate change would occur and quickly decided it wasn't, as exactly like the doppler effect and a siren, the sound is at the highest pitch when the siren is closest to you. In that way, the pitch of the siren can tell you when the siren is closest (if the pitch doesn't drop then the siren will collide with you). When stationary and tracking a target, the point it will be closest to you will be when the target's AoB is 90 (port or starboard) as that is the point at which its position on the track is the closest to your position. So, now we know that, we can measure and record the time it takes for the bearing to change a fixed interval (say five degrees) and then use that to determine whether target's bearing rate has decreased, which means that the target has passes an AoB of 90. When we have the relative bearing at which the target's AoB was 90 (within a maximum error of two and a half degrees), we can then use our own course to determine tha target's course. When we have the target's course we can the match that course and use speed matching to hold the target on a constant bearing to determine the target's speed. So there you have it, a simple method that needs no plotting and no range finding in order to determine target course and speed. It will work for sonar bearings, but to speed match you will need to have an optical bearing if the target is travelling faster than seven knots. If you have radar, this will also work, but you might as well plot. The disadvantage to this method is that you will always have to surrender a position ahead in order to determine when you are behind the target's beam, but you shouldn't be too far behind and if you aren't fast enough to catch, then you won't intercept. Anyone see any holes? Apart from not being able to determine range? __________________ -------------------------------- This space left intentionally blank.