TMA
I don't know if we talk about the same thing but the speed-distance ruller, is a line divided in steps, which is the distance in yds that the target covers in 3 minutes. The ruller is initially matched on the first plotted bearing and then by rotating it you match it with the rest bearings that you have to plot every 3 minutes. Of course:
a) The scale of the ruller has to be the same of the map.
b) You have to plott at least 3 bearings before you match the ruller.
c) You try diffrent speeds in order to match the ruller on the bearings
d) You try diffrent rotations for the same reason
e) If you have a lot of solutions, by turning tha submarine, the deviation of the bearing rate will reject the incorrect solutions.
f) You may know the heading/distance of the target visually so you can apply them
h) Finally ypou have: Distance-Speed-Coarse!
This is called STRI PLOT and it is used since WW1 untill today in all submarines in the world!
You can find it in Dangerous Waters in TMA station!
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