target speed: the eighty-ten method

[Diopos]

Although the 8010 method as presented here seems to be a "no-go", Grayrider introduced a solid base to use the sub as a "navigation tool" to establish a target's speed and course. This is not a a "how to ..." presentation. I will only give a rough description and explain why it is doable.

The main element: Attaining a collision course.

When the sub and the target are at a (converging) collision course the bearing under which the target is observed remains constant. (Valid for constant course and speed.)

As analysed in previous posts in the this thread attaining a collision course by itself is not enough but a more "compound" approach is completely doable.

Outline of the """method""" (for a converging target):
- Attain a collision course and note target bearing (b1) and sub's speed (u1). Sub is at Target's AoB ...well AoB1 (unknown)
-Stop sub or lower its speed
-After a while start increasing speed (incrementally) until target bearing stabilises again note target bearing (b2) and sub's speed (u2).Target's AoB is AoB2 (unknown)
Note: sub has not changed course.
if the target moves at speed v (unknown) and the intercept angle between target and sub's course is w (unknown) then the following are true:

AoB1+b1+w=180° (eq. 1)
AoB2+b2+w=180° (eq. 2)

___u1_____________v
------------- = -------------- (eq. 3)
sin(AoB1)_______ sin(b1)


___u2______________ v
------------- = -------------- (eq. 4)
_sin(AoB2)_______ sin(b2)


So 4 equations, 4 unknowns the problem is solved (theoretically).
Plus the required maneuring is completely doable with fairly clear-cut criteria (stabilizing the target's bearing).

For people that have fiddled around Target Motion Analysis this may seem elementary but hey I'm an amateur

I remind you this "analysis" just shows that the method is doable.
BTW if u1=u2 it means that you're running parallel to the target (and that v=u1=u2).

Fire away now guys!.


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EDIT: here is a link with a diagramm for the above: link



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