These instruments revolutionized position-finding at sea. Finding longitude greatly improved once better angle-measuring instruments and star charts were available. Explore More.
Mask ». Chart showing Nova Scotia to Cape Cod ». The Clipper Ship Flying Cloud ». Sextant ». All of the bodies were rising in the sky to a high point above the horizon and then setting again in the west. The highest point was due north or south in the sky and always occurred at the midpoint between when a body rose and set, and this midpoint was a constant reference as it occurred at the same time each day. It was one of these midpoints, along with Harrison solving the technical problem of creating a clock that kept time accurately for days on end, which helped provide a practical solution to the longitude problem.
The point is called local noon, the point at which the sun was highest in the sky. Whereas sunrise and sunset change time each day, local noon was always the same time and thus a precise reference point for checking time each day wherever you were.
If you could then just check your time against the time at another known location, you could calculate your longitude relative to the known location. In fact the high point of other bodies could do this as well, but the sun was an obvious one.
Local noon at the prime meridian of 0 degrees, which passes through the Royal Observatory at Greenwich in London, eventually became the accepted datum for longitude and time, leading to the well-known term Greenwich Mean Time. You can read more about that, along with some other intriguing issues that had to be resolved, and explore some wide-ranging background to time, distance and speed in the digital story Longitude — A story comes full circle.
David Payne is Curator of Historic Vessels at Australian National Maritime Museum, and through the Australian Register of Historic Vessels he works closely with heritage boat owners throughout Australia researching and advising on their craft and their social connections. He has had a wide sailing experience, from Lasers and foot skiffs through to long ocean passages. Since he has been able to work closely with Aboriginal communities on a number of Indigenous canoe building and watercraft projects.
Explore Blog. Posted on 22 Jun by David Payne. We may delete posts that are rude or aggressive, or edit posts containing contact details or links to other websites.
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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. Used with permission. Become an OU student. Copyright information. Publication details Originally published : Friday, 25th August Last updated on : Friday, 1st March
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