NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Longitude by altitudes. was Re: How Many Chronometers?
From: Marcel Tschudin
Date: 2009 May 8, 15:28 +0300
From: Marcel Tschudin
Date: 2009 May 8, 15:28 +0300
I din't seriously follow the thread on "How Many Chronometers?". After George did change its title it draw my attention. A few days ago I informed you under "Old map" on a book which I received as a present and that it requires some caution to appreciate its content. Since this book was published first in the mid 60s you may likely have read it a long time ago and probably also followed discussions on its pros and cons. Sorry that I'm sometimes late, but for me the content is new. Now, why do I mention this here? The main content of the book deals with the map of Piri Reis from 1513 which only was found in 1929. This map shows with an amazing accuracy also the east coast of the American continent. One presumes(?) that Columbus used a map from Piri Reis on his trip. The map which was found mentions apparently that it was made from even older maps. According to our "general" understanding it requires good means to measure the time (chronometers) for being able to determine the longitude and thus being able to draw an accurate map. However the chronometers were only invented in the middle of the 17th century. If the date of the Piri Reis map is really correct, raises the question on how the longitude may have been determined before the time of chronometers we now of. It looks like there must have existed previously either accurate means of measuring the time OR an other mean of measuring longitude, like e.g. the one indicated by the new title of this thread "Longitude by altitude". That's the reason why the title of this thread draw my attention. However, reading George's comments shows the drawbacks of this method; as a consequence one may question whether this was really used. The members of NavList know that I'm a member without any navigational experience. I'm therefore interested to see how you, who have this experience, look at this. Marcel P.S: For those who don't know the map from Piri Reis; just Google for it. --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---