Advanced TMA help

[jmr]

I've been practicing advanced TMA against a known target (speed and course checked in the mission editor) and I think I could use a few pointers in refining my solutions.

Here's a pic of solution I worked out.



For starters I set my range circle to 20KM as I think that's the known range where the sonarman will start reporting contacts. I begin taking bearing readings every 5 minutes for a total of 25 minutes of which I plot in Mobo. Once I work out the target's course I predict where he'll be in the next 15 minutes. From there I jet off in another direction (I think it's called across the line of sound?) for 15 minutes and then stop to take another bearing. From there I should be able to triangulate the target's position.

The red contact marker shows my new position after my 15 minute run and the red circle denotes the triangulated position. Am I correct so far? If that is indeed correct my next question is how do I determine the target's speed just from that triangulation?