I highly recommend that you abandon the Notepad Method.
You may wish to employ a "dry run" to obtain Target Speed, using the Splitlog Formula.
An AOB of 90 degrees to the target is best, but NOT required.
If your close to disecting the targets track at 90 degrees, you don't have to stop either.
Identify your target.
Get in your best "guesstimated" position to disect the targets track, at 90 degrees.
Slow to 1 or 2 knots, to avoid detection.
Point your Periscope or UZO at 000.
When the targets bow reaches the 000 mark, start the Stop Watch.
When the targets stern reaches 000, stop the Stop Watch.
(The same Stop Watch that times your torpedoes).
That number will remain on the watch, until you remove it, or fire a torpedo.
Go below, and do your homework.
(1.852 x targets length in meters)
divided by time in seconds on the stop watch
equals speed in knots.
Now you have his speed, without having to rely on that notepad nonsense.
(Depending on how exact you want the result, you can round 1.852 to either 1.9 or just plain old 2.)
Time invested in getting his exact course is also well worth it.
Much better than trying to guesstimate his AOB.
Hope this was helpful.
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