calculating speed
 

there was a great formula i used by donreed1, it had numbers 3600 and 1824? Anyway it was very accurate and does anyone no where to find this formula? Thanks

I'm not sure, but 1824 sounds a lot like the number of meters per nautical mile, which is 1852m. This means that 1 knot will cover 1852 m in an hour. Any equation that includes this number basically caclulates a conversion between meters and nautical miles/knots.

I have a few calculations I use for measuring knots based on distance travelled over a measured time.

One of them is:
1.943 x meters per second=knots
or
0.032 x meters per minute=knots

Use this conversion after plotting target position, starting a stop watch then plotting target position again after a certain time period and measuring the distance he covered in that time period and plugging that into the formula. If you measure a target having travelled 800m in 5 minutes the formula would be:

0.032 x 160 = 5.12 knots

You get 160 by dividing 800 by 5 - the number of meters per minute.

This obviously requires having a calculator. Thats how I do it though obviously its not very realistic since they didnt have a calculator like I use, though someone doing some basic math on paper would be perfectly fine if not a bit longer to do.

This is somethign I do because I don't like being tied to the 3 minute 15 seconds rule. It means I can do it in minutes or even seconds, so I can do a fast and dirty speed calculation in 40 seconds if I want or if I miss my 3:15 mark I can just carry on to 4 minutes and be just as accurate.

There are formulas that are simpler to do in your head, which might be what you're looking for, but I never ran into them I guess. I'm always looking for new ways to figure these things out though, so I hope someone has what you're looking for. Just thought I'd throw mine in there too. :up:

thanks for the reply