Anyone know why SH4 and TMO doesn't specify ship length in the Recognition Manual? Otherwise you could line up the vertical line of your periscope with the front of the ship, start a timer, and measure the time it takes for it to get to the rear. Now if that distance is a known, you can divide it by the time taken to get a value in m/s. And to get a rough knot value, you simply multiply that by 2. (i.e 10m/s = 20kts)
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