Thanks Hitman for the suggestions, but the ship I was tracking had a length of about 140m or so, so I used the 150m scale and choped off a tiny bit and it still read 6-7 knts when she was going about 2-4. I'll have some more goes at this, but I am not understanding how this can work everytime esp if the ship is going really slow...then it takes a relatively long time for the ship to pass and who is to say whether the needle will land on 2knts or 18 kts...I don't understand how exactly the chrono calculates the speed, but that doesn't mean I won't keep trying to find out.
Is there any kind of time limit, i.e. what if the ship takes more than 1 minute to pass (say it takes just over a minute and a half to pass...this would suggest a slow speed to me, but the needle would be over on a higher number of the scale (say 5-10kts, when it should be about 2kts.) Wouldn't the range also affect the time/speed relationship? Is there a range limit? also what about AOB--?
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