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Originally Posted by vanjast
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Originally Posted by Platapus
We don't want your kind in the US Navy  |
The Village People never convinced me to join the US Navy.. 
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Originally Posted by Platapus
Speed (kts) = 1.94 x Length of ship (meters) / Time (seconds)
A simple conversion could be made for the ship length in feet (I am a metric type of guy myself). The advantage of this formula is that it is range independent and works pretty good for AoB under 45.
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This looks like it's the same idea except I put it in table format. I'm going to change this to a sliding ruler/circular chart thingy. It looks likes that formula gives an approximate reading, where as I'm looking for 'pinpoint' accuracy  .
This is been geared for RFB where where you hit a ship matters. |
If I understand your second table right you want to measure speed by timing how long the bow (or whatever part) crosses 1, 2, 4, or 8 degrees in the scope? Right? Well, you need a range to the target for that, as a degree at 1nm is smaller than say 4 nm. The 4 collumns alow to correct for this range but would be cumbersome in use. And loose accuracy.
The formula that Platapus gives is as accurate as the identification you make and what's in the recognition manual. And what's really great, range is no issue at all. It is sensitive to your movement though. To avoid that, it requires having the periscope at 0 or 180, and being on course that is just infront of the target bow. You let the target pass an imaginary wall (immovable since you move along it) in the ocean made by the vertical periscope line. The target's own length determines the speed by how long it takes to cross it. Simple as that. No range or AOB to correct for. Only with near-bow and near-aft AOB it is difficult to measure since you can't see the begin and end of the ship as the structures and sides are in the way. But between 20-160 it's usually good. I would say this method is much more 'pinpoint accurate' as the one above.