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[geordief]

Depth in modern nautical charts is expressed in metres.

The fathom is just one of many old units of measure, deriving from the times when trades and professions were much more self-contained than today, so the need to compare measures across different applications was far less. According to Wikipedia, the fathom seems to go back to the Ancient Greeks (ὀργυιά, meaning "outstretched" - the distance of a man's outstretched arms, approx 2 m or 6ft.).

Wasn't the "knot" based on an old method of measuring speed at sea wherby a rope with knots tied at regular intervals was thrown into the water and the knots counted as they were pulled off the deck by the current?

(thought I heard something along those lines)

 

[DaveC426913]

Yes.

 

[Write4U]

Wasn't the "knot" based on an old method of measuring speed at sea wherby a rope with knots tied at regular intervals was thrown into the water and the knots counted as they were pulled off the deck by the current?

(thought I heard something along those lines)

knot
measurement

The term knot derives from its former use as a length measure on ships’ log lines, which were used to measure the speed of a ship through the water. Such a line was marked off at intervals by knots tied in the rope. Each interval, or knot, was about 47 feet (14.3 metres) long. When the log was tossed overboard, it remained more or less stationary while its attached log line trailed out from the vessel as the latter moved forward. After 28 seconds had elapsed, the number of knots that had passed overboard was counted. The number of knots that ran out in 28 seconds was roughly the speed of the ship in nautical miles per hour.

https://www.britannica.com/science/knot-measurement

 

[Saint]

1 knot = 1.852 km/hr = 1.15 mile/hr
1 nautical mile = 1.852 km = 1.15 mile