Spiess TMA (aka Four Bearings)

B_K · 10-25-17, 12:40 PM

In my post I don't mean the final target solution which is achieved by locking any of those estimates. That's true ofc.

but

What I mean is that:
bearing lines alone intersect often in one point, which could help simplifying geometric calculations. When this is the case, only two first real bering lines are enough to use Spiess method. Instead of collecting third bearing for real, you can draw a Spiess line from the place where your uboat would be if you maintained current course and speed, and conduct the line through the common intersection point. Such a line is a Spiess line which is equivalent to assumed 3rd bearing if you didn't change course and speed, went there and collected it.
But in the meantime you turn the boat and by triangulation you collect real 4th bearing, intersecting freshly made Spiess line. You have target position and continue the procedure as in normal method.
However you just saved one time interval, which in turn can save your approach.
The point is - how do you know, having only two real first bearings, if all future bearings and Spiess lines go through one common intersection point.

It is defined by certain target-uboat geometry and Line of Sight parameters such as speed components and angles. Those conditions I would like to discover

EDIT:
Ok, I think I am closer to that.

page 42:

https://www.globalsecurity.org/milit...14308_ch10.pdf

describes Lagging geometry, where simplified Spiess could be utilized. I don't know yet if it's enough if speed vectors are just opposite, or should have specific component and angles proportions. But it is a good starting point.

10-25-17, 12:40 PM	#10
B_K Bosun Join Date: Nov 2011 Posts: 68 Downloads: 63 Uploads: 0	In my post I don't mean the final target solution which is achieved by locking any of those estimates. That's true ofc. but What I mean is that: bearing lines alone intersect often in one point, which could help simplifying geometric calculations. When this is the case, only two first real bering lines are enough to use Spiess method. Instead of collecting third bearing for real, you can draw a Spiess line from the place where your uboat would be if you maintained current course and speed, and conduct the line through the common intersection point. Such a line is a Spiess line which is equivalent to assumed 3rd bearing if you didn't change course and speed, went there and collected it. But in the meantime you turn the boat and by triangulation you collect real 4th bearing, intersecting freshly made Spiess line. You have target position and continue the procedure as in normal method. However you just saved one time interval, which in turn can save your approach. The point is - how do you know, having only two real first bearings, if all future bearings and Spiess lines go through one common intersection point. It is defined by certain target-uboat geometry and Line of Sight parameters such as speed components and angles. Those conditions I would like to discover EDIT: Ok, I think I am closer to that. page 42: https://www.globalsecurity.org/milit...14308_ch10.pdf describes Lagging geometry, where simplified Spiess could be utilized. I don't know yet if it's enough if speed vectors are just opposite, or should have specific component and angles proportions. But it is a good starting point. Last edited by B_K; 10-25-17 at 12:55 PM.