Quote:
Originally Posted by B_K
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. |
i will have to disagree with you on this. Having three bearings intersecting to one point is an extremely rare situation like winning the lotto.
I understood what you are seeking for from your previous message.According to my point of view,without knowing anything else from target's data (speed ,course or range) don't expect for a solution.
The Spiess Line is the locus of all possible positions of target at the next time interval.At the case of having three bearings ,Spiess proved that ,at the fourth time, this locus is a straight line (ok,i know you know that) but (going to your theme now) , at the case of having only two bearings (and nothing more) the locus ,at the third time, is NOT a straight line (in fact there is no locus at all).By 'demanding' the third bearing ,at the third time, cross by the intersection point of two previous bearings,you are narrowing the theme to one specific situation.
Look at the following pic:
the blue bearing is the bearing from where your sub will be if you maintain course and speed.(as you can see is not pointing to the correct position of target)
the red bearing is from the point that your sub should have been in order to point to the correct position of target.
The only one specific situation that these two bearings matches and crossing from the intersection point of two previous bearings is when both courses (yours and target's) are parallel (look at pic below).
As long as both speeds are constant this is independent from speeds or ranges.
