Phoenicians relied on primitive charts as well as observations of the Sun and stars to navigate their vessels to destinations. In the later period, the Phoenicians and their successors, the Carthaginians, also invented a tool known as the sounding weight.
Made of stone or lead, this bell-shaped tool had a very long rope attached to the tallow inside. Sailors used to lower this weight into the bottom of the sea to determine how deep the waters were, and, using this measurement, to estimate how far they were from the land.
In addition, the tool, with the help of the tallow inside, could pick up sediments from the seabed, which enabled expert sailors to decide the location of their vessel.
However, centuries passed before the use of a standard method to measure the distance and speed during navigation at sea. A number of new techniques and methods were experimented with from time to time, making marine navigation more meaningful.
Until the fifteenth century, coastal navigation was mostly in practice, since the open sea voyages were limited to regions of predictable winds and currents. Further ventures by the sailors were enabled by the development of scientific and mathematically-based methods and tools in the following years. The invention of the sextant, the chip log and Chronometers, etc. And, the modern era saw the replacement of ancient navigational tools with electronic and technological equivalents and also the determination of standard measures including Prime Meridian.
With the help of new technologies, from Gyroscopic Compass to GPS, now marine navigation has become more systematic and easy. Years after the use of several techniques to determine the position and speed of a vessel, British mathematician Edmund Gunter succeeded in enhancing navigational tools including a new quadrant to define latitude at sea.
Gunter claimed that the lines of latitude can be used as the basis for a unit of measurement for distance. Eratosthenes and his successors had already assessed the circumference of the Earth, helping other mathematicians to build on.
Using the circumference of the Earth assessed by Dutch scientist WillebrordSnellius aka Snell- who assessed it at 24, Roman miles or 24, statute miles -Gunter defined a nautical mile as 6, feet meters , i. Even decades after these developments, there was no standard definition of a nautical mile and different countries had different definitions to follow until It was in , at the First International Extraordinary Hydrographic Conference in Monaco, the international nautical mile was accepted as exactly as 6, feet 1, meters.
Currently, this is the standard definition of a nautical mile in use and is accepted by the International Hydrographic Organization and the International Bureau of Weights and Measures. A nautical mile is based on the circumference of the planet Earth. If you were to cut the Earth in half at the equator, you could pick up one of the halves and look at the equator as a circle.
You could divide that circle into degrees. You could then divide a degree into 60 minutes. A minute of arc on the planet Earth is 1 nautical mile.
This unit of measurement is used by all nations for air and sea travel. It's a mathematical calculation based on degrees of latitude around the equator. The equator is a circle, which we know has degrees. Each degree is divided into sixty minutes, which are not the same as the minutes on your watch. In navigation, one minute is called a nautical mile.
So each degree of latitude is sixty minutes or sixty nautical miles. Nooks and crannies. Semantic enigmas. The body beautiful. Red tape, white lies. Speculative science. This sceptred isle. Root of all evil.
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