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All rights reserved. The Open University is authorised and regulated by the Financial Conduct Authority in relation to its secondary activity of credit broking. Skip to content Study with The Open University. Search for free courses, interactives, videos and more! Free Learning from The Open University. Featured content. Free courses. All content. Latitude and Longitude Updated Friday, 1st March Longitude Great minds had tried for centuries to develop a method of determining longitude.
Global positioning systems Today, it's all done electronically through GPS, a world-wide radio navigation system made up of a constellation of 24 satellites and their ground stations. Further reading. Article Level: 2 Intermediate. Copyright: OU.
Article Level: 1 Introductory. Study a free Geography course Used with permission. Schaffer described how a Yorkshire carpenter named John Harrison became an unlikely hero of the quest to measure longitude. Submitting his initial design for a sea clock in , Harrison lobbied the board with improvements for the next 40 years. His H4 model - now displayed at the National Maritime Museum - accurately told longitude while withstanding a variety of temperatures and pressures.
Unfortunately, the clock was incredibly difficult to make. It requiredexpensive diamond palettes and took Harrison more than six years to build. The board needed a design that could be rapidly produced en masse. Watchmaker Larcum Kendall simplified the H4, creating a design that could be manufactured by many clockmakers. Industrialisation meant that parts and tools could be produced according to standardised measurements. ANMM Collection: However, latitude, or the same thing by another name, has been widely used by humans since they took to exploring the oceans and maybe even earlier, perhaps as people moved to new places on land, leaving a locality with known landmarks.
This is because latitude has an obvious reference in the sky — a map or chart featuring the sun during the day and the stars, moon and planets at night. As you move north and south, the map in the sky changes. Their relative position as they rose and set was simple enough to observe, but also their height above the horizon changed as you moved north and south, and this could be estimated or even measured with quite reasonable accuracy by different methods.
Willem Blaeu is renowned for the quality of his charts and cartography which represent some of the most accurate work of the 17th century. This whole reference in the sky formed a chart of its own, and although it changed through the night and through the seasons, and even presented a different view of the bodies depending on your location, the changes were all gradual and formed a pattern which many communities and civilisations were able to observe and record, often in stunning detail and insight.
This accumulated knowledge and understanding was passed on and people were able to determine anything from a broad indication through to a reasonably precise location of where they were in a north-to-south direction, either relative to another known point or, in later times, relative to the equator. The quest for determining longitude developed a number of possible methods, three of which were potentially quite accurate. Also, the concept of using the difference in time between a known location and your location as a means of calculating your longitude was also widely known.
The Moon as a clock When measured against the background of stars, the Moon moves by approximately its own diameter in an easterly direction each hour. In , Johann Werner of Nuremberg suggested using the Moon as an astronomical clock. The satellites of Jupiter Meanwhile, in , not long after the invention of the telescope, Galileo discovered the four largest moons of Jupiter.
He and others soon observed that eclipses of the moons occurred at what appeared to be regular intervals and suggested that the difference in time between the observed and predicted time of occurrence at a standard meridian would enable longitude differences to be measured.
In , Galileo submitted this method to the Spanish in an attempt to win their longitude award, but failed to persuade them of its merits. When the Dutch offered a longitude prize he turned to them but was again unsuccessful.
Through regular observation, Galileo gained a greater understanding of their motions and with this knowledge was able to improve his tables of predictions. As a means of finding longitude at sea, the method failed: not only did the telescopes prove impossible to use on a moving ship, but when Jupiter is close to the Sun, there is a period of about ten weeks when it becomes invisible.
However, following the invention of the pendulum clock and the introduction of more accurate tables by the French astronomer Cassini in , the method was widely used to improve maps and charts. The method remained in use until the start of the nineteenth century.
What Morin proposed was a more refined form of what has become known as the lunar-distance method, previously proposed by Werner, taking into account both refraction and lunar parallax a small shift in position that varies with the location of the observer.
The Commission deemed that with the present state of tables of the Moon and stars, the method could not be used in practice. A Frenchman, that called himself Le Sieur de St. Pierre, having some small skill in astronomy, and made an interest with a French lady, then in Favour at the Court, proposed no less than the discovery of Longitude. They too were based on the position of the Moon. Based on his own observations, he had been able to show that the best available star catalogue, that of Tycho Brahe, was prone to errors, which meant that any longitude found could be in error by up to several hundred miles.
To provide the necessary data, he said, would require years of observation with large instruments fitted with telescopic sights. He explained how observations of Io in had shown that the difference in Longitude between Greenwich and Hoai-gnan, a city on the east coast of China was about 10 degrees or miles less than had been previously thought. For the first 14 years, there was almost no progress, for although Flamsteed had been provided with a range of instruments; none was up to the job.
It was only when he came into money following the death of his father that any real progress was made. The first recorded observation was taken in and the last shortly before he died in
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