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Speed Log, Speedlog, Knot Meter, and Marine Electronics

The first known device to measure speed is often claimed to be the Dutchman's Log. An object that would float was thrown overboard and the time required to pass between two points on deck was measured with a sandglass. However, the first reference to a Dutchman's log is in 1623, after the ship log. The Dutchman's log could be used with a brass tobacco box, rectangular with rounded ends. This box had tables on it to convert log timing to speed. The log has been used by mariners for a long time. The first occurrence of a description of the device in print was in A Regiment for the Sea by William Bourne in 1574.

Initially, the log-line was not knotted and the length was measured directly on the line. With the introduction of the nautical mile as a standard unit of measure at sea in the 15th century, the line began to be marked at equal intervals proportional to the nautical mile and to the time interval used for measurement. Initially, the markings were in the form of knots in the line. Later, knotted cords were worked into the log-line.

Although the unit knot does not fit within the primary SI system, its retention for nautical and aviation use is important for navigational reasons, since the length of a nautical mile is almost identical to a minute of latitude. As a result, distance in nautical miles on a navigational chart can easily be measured by using dividers and the latitude indicators on the side of the chart.

Nautical speed is sometimes erroneously expressed as "knots per hour" which would actually be a measure of acceleration, as in "nautical miles per hour per hour."



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Speed Log, Speedlog, Knot Meter, and Marine Electronics


Speed Logs - Marine
Speed Log, Speedlog, Knot Meter, and Marine Electronics The first known device to measure speed is often claimed to be the Dutchman's Log. An object that would float was thrown overboard and the time required to pass between two points on deck was measured with a sandglass. However, the first reference to a Dutchman's log is in 1623, after the ship log....
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Furuno Speed Logs

JRC Marine Speed Logs

All Products Index in Alphabetical Order

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