How do you measure knots?

Question

how fast does a ship travel if measued in knots

??

Answer 1

knot speed was originally measured using what is called a chip,  a triangular wooden piece that had a weight on one part so that it floated in a basically vertical position.  this acted as an anchor and the line fed out for a measured time using an hour glass.  The number of knots that were pulled through the hand was the measure of speed.

in order to measure speed in a vessel today, 2 different technologies are generally used (not talking about gps in this)

the first is the use of a small wheel that has a magnet in it and as the magnet goes across a reed switch, it sends a pulse that measures the speed by the number received.

the second one is by use of a tuned circuit that measure the decrease of power from the circuit as the vessel moves through the water, more speed, more energy taken.

after that, there are as many ways to measure speed as the human mind can think of.

the most accurate will always be, distance made good, divided by time.

many things affect the speed of a ship or surface vessels, and a ship moving from point a to point b with a parabolic curve in the rhumb line route may actually be moving faster than one expects if the vessel travels further than expected and still runs the course in a short time.

lots of facts affect speed, like hull length, draft, and power output

Answer 2

A nautical mile is not a linear or statute mile.  A nautical mile is an angular measure; one minute of arc on a great circle.  There are many coastal and a few celestrial navigation methods to measure distance travelled over time.

Answer 3

Knot is a shorthand term for nautical miles.  A nautical mile is 6,000 feet, as opposed to a land mile of 5,280 feet.  Accordingly, a ship traveling at 10 knots will cover 60,000 feet in one hour or a little over 11 miles per hour in land miles.

Answer 4

The device that sailors used to make their speed measurement was called the "chip log".  Chip as in chip of wood, and log as in to record in a log.  The chip was a wedge of wood about 18" in size; it was tied to one end of a rope on a large spool.  The rope had knots tied into it about every 47'3" (more about how that was calibrated below).

The wooden chip was thrown overboard at the ship's Stearn (back end).  Because of its wedge shape, it would "grab" the water and start pulling out rope as the ship moved forward at some yet unknown speed.  One man would hold the spool of rope as it played out; another man would start a sand glass filled with 30 seconds of sand; and a third man would count the knots as they passed over the Stearn board.  When the 30 seconds of sand expired, the time keeper would call out and the counting of knots would stop.

Answer 5

a knot is a nautical mile in an hour, or 1.15 statute ( land ) miles an hour.

Answer 6

To measure a knot you need to divid the speed into 1/4