I usualy plot the speed with the stadimeter. I do it severel times durring the Normal Approach Course or Optimum Approach Course from ranges of 7000 yards and in.
This gives you plenty of time to do lots of 3 min checks. I use the circle tool to plot the contacs, having the arrow part showing direction of travel of the target. Say i then have like 5 x 3 min plots over 15 min's i have the option of comparing them, and/or making an average (take the first plot's circle and enlarge it untill the edge of the circle intersects with the center of the last plot - divide the circles diameter with the total time from start plot to end plot and multiply that with 3 and divide with 100.
I have Cource Calculator slide rule next to me. Before starting my plotting i turn the wheel to my own course. From then its easy to very fast get a true to north bearing on the target from the wheel. What i doo is this:
1) NavMap Centered on sub
2) change to Stadimeter - make sure the left side TDC is open on the selection that shows ranges is present.
3) make sure you take the stadimeter range for the correct item (i use funnels) using the correct stadimeter setting (i use the manual input option on the masthead height)
4a) Scope up (All the way so it clears fast)
4b) take a bearing/range and note it on paper fast - estimate AOB
4c) Scope down (only untill its just under water - then stop it)
5) start stopwatch (only the first plot naturaly)
6) NavMap - linetool click on sub fast
7) ease off as from now you have 3 min's to make this plot before the next is up.
8) plot by extracting the line from the sub too the correct range read off the TDC and then i make a 300 ft. circle there. I let the radius arrow in the circle point in the way of travel.
I know the stadimeter is not the most presice tool, but for getting the speed correct in 3 min plots its mighty fine and more precise for us than it was in reality.
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