This video has shown me the problem, by way of the equation he is using to calculate speed. I've always used the rule of distance traveled in 3 min 15s, divided by 100 to get speed in knots. This correlates to the following equation:
(l/t)*1.95 where
l=distance in meters
t=time in seconds
But the video uses: (l/t)*1.852
When one searches how many meters in a nautical mile they get 1852. I think the 3m 15s rule is derived from a so called international knot which is slightly different.
So on my shot, i figured he moved 700 m in 3m 15s, which i entered as 7kt. But according to the videos equation. It was more like 6.6 kt. At 900 m away, that might have been the difference.
Using the video's equation, it should be distance in 3m 5s divided by 100.
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