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View Full Version : How exactly do I find the speed of a ship...

WNxScythe
12-30-2005, 06:57 AM
...with the chronometer? I always get ridiculous speeds like 234knts or 0knts when a boat is clearly moving.

WNxScythe
12-30-2005, 06:57 AM
...with the chronometer? I always get ridiculous speeds like 234knts or 0knts when a boat is clearly moving.

vanjast
12-30-2005, 07:15 AM
Somewhere in the forum there is a Rev/Speed table on most merchant ships. you listen and count the revs on sonar, ID the ship and then you have he speed.
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Messervy
12-30-2005, 01:07 PM
Here:

http://img.photobucket.com/albums/v675/Messervy/Speedchart.jpg

Hoatee
12-30-2005, 01:11 PM
Patience is a virtue indeed.

lecek
12-30-2005, 01:28 PM
If you are using the notepad by the scope to find speed you need to be aware of two things.

1) Finding range to target makes a big difference. If you are 25% off the range, you will be 25% off the speed.

2) AoB can make a big difference. AoB is different then speed as all you need to do is be close. But the farther off your AoB is from the actual AoB the bigger the difference. In extreame cases you can have a ship doing 1 knot show up as hundreds even with a good range measurment just because your AoB is off. (In this extreame case you would need to be off almost 90 degrees.)

Taking your time to get as good a range finding and AoB setting as you can will bring your speed measurement into reality.

PS, it is best to do the above measurements while not moving (or moving slow) and closer to 90 degrees AoB. I would say about 45-70 is good enough.