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Are Dava Sobels' books "Longitude" (which I thought was history wrapped in a historical novel) and "A True Story...." the same book? DJ Clayworth 15:07, 20 Oct 2003 (UTC)
In the article it says that the prime meridian is the one passing through Greenwich. Is that still true? I thought the prime meridian had moved 90 feet and the line marked at Greenwich is no longer valid. Is not the prime meridian for UTC the 90 deg one in Chicago? Does ANYONE still use GMT?
Drg40 (
talk)
13:59, 13 May 2012 (UTC)
This article says longitude runs between +180° and −180°, but it does not say whether east or west is positive. I had always thought that it was standard that west is positive, never suspecting until a couple of hours ago that anyone used the other convention. Then I saw Wikipedia's list of earthquakes, which does use the opposite convention. As I stated on that article's discussion page, I once heard the head of the math department at MIT (David Vogan, who has since been succeeded as department head), speaking before about 150 undergraduates, state that it's appropriate that longitudes in Europe are negative since Europe is a cultural cesspool. No one responded that east longitudes are positive and west negative. (Nor did anyone complain about that characterization of Europe.) So I'm not the only one to think that's standard. Michael Hardy 02:35, 3 Jan 2005 (UTC).
So whoever wrote list of earthquakes had it wrong, then. Michael Hardy 03:21, 4 Jan 2005 (UTC)
WGS84 has longitude positive eastward, negative westward. Urhixidur 14:11, 2005 Jan 4 (UTC)
From a strictly mathematical point of view, our usual standard is to use a right-hand coordinate system, in which angles are measured in a counterclockwise fashion. -- Jacobolus 00:10, 15 Feb 2005 (UTC)
I am curious, however about all the fuss with clocks. Yes, clocks are great and solve the longitude problem. I have taught that. But the motion of the Moon in relation to the Sun and to the stars can be used to tell time, too. Just occurred to me that though it's a bit complicated and not quite so accurate, it might work to low accuracy, but good enough for simple navigation, say within a few degrees longitude.
Pdn 05:19, 25 Feb 2005 (UTC)
Moon/Mars picture/text problem: While the diagram of the moon and Mars shows how they would not appear to be lined up from a position to the west, it shows the Moon appearing to the east of Mars, while the text describes Mars as being to the east. Where's the error, and should this be explained? Piledhigheranddeeper ( talk) 19:04, 9 December 2008 (UTC)
I have removed the reference to shipwrecks in Western Australia, since only 5 are known of in early times: English East India Company's, Trial (1622), the Dutch East India Company's
Batavia (ship) (1629), Vergulde Draeck (1656), Zuytdorp (1712) and Zeewijk (1727). For these early wrecks I dont know to determine the role of longitude navigation errors as opposed to chart errors (uncharted reefs) and other causes. Anyway ship wrecks were occuring in many parts of the world, motivating the search for a solution. -
Op. Deo
20:18, 23 August 2005 (UTC)
The clocks were not so good, but could not the ancient mariners have measured time by the motion of the moon, at least when it's visible at the same time as the sun, so you can get the angle between the two? Pdn
Yes this is the method of Lunar Distances which was the practical competitor to Harrison's chronometer in C18. It was at first limited because the orbit of the moon was not known by ship's officers. But eventually suitable tables were produced which made it easy to measure the moons position relative to certain stars on the ecliptic and determine local time, and therefore longitude. It was then cheaper to provide ships with a set of tables and a sextant, rather than a very expensive chronometer modelled on Harrison's design, So in some ways the impact of Harrison's successful toil was limited. - Op. Deo 22:29, 23 August 2005 (UTC) Thanks. I just saw that Galileo devised a method of using the Moons of Jupiter. see [2] which says: "For Galileo, his admonition marked the beginning of a period of silence. He busied himself with such tasks as using tables of the moons of Jupiter to develop a chronometer for measuring longitude at sea. He endured his rheumatism, ..." Pdn 04:40, 24 August 2005 (UTC)
Latitude says that they are not "exactly" equal to 1 nautical mile whereas this article says that Latitude is "exactly" equal to 1 nortical mile! This seems to be to be something that needs clearing up. —Preceding unsigned comment added by 58.105.29.26 ( talk • contribs)
The 4th paragraph should be changed, both because it is factually wrong (twice) and because it contradicts the entry under "Latitude." This creates confusion and introduces uncertainty as to which is correct. The differences may seem small but I was led to this entry while trying to resolve an apparent error in the ground track of a satellite orbit simulator. The error was resolved by using the correct definition of latitude as shown by the Wikipedia entry for that parameter (as opposed to the one implied here.) Mennochio 23:38, 30 July 2006 (UTC)
I agree. I also suspect it is worth pointing to nautical miles, statute miles, and the Great Circle Distance Formula in the same discussion. As is, the formula for equivalency in one long. deg. is misleading (i.e., are degrees in radians? do I get km, really?) 71.236.220.71 16:31, 25 October 2006 (UTC)
I think the article should emphasize the primary purpose of longitude: that together with the latitude it uniquely identifies any point on the surface of Earth (or other celestial body). This is mentioned only in the third paragraph, saying
and in the link to Geographic coordinate system in the See also section. I am not sure yet how to change the article to emphasize this more, so I did not edit it. – b_jonas 21:08, 19 June 2006 (UTC)
How many miles is 15 degrees (1 timezone) of longitude? -- Homfrog Tell me a story! 00:41, 30 December 2006 (UTC)
I suggest a fork of the section ==History of the measurement of longitude== to a new article named measurement of longitude (as a starter).
The German article de:Längenproblem discusses also earlier geometric methods as well as the more curios proposals (firing cannons, injuring dogs and the like), while this article, as well as Board of Longitude and John Harrison, cover much of the same. -- Matthead discuß! O 09:04, 25 July 2007 (UTC)
There are very few dates given in this section. I wanted to know when Harrison built his various chronometers, when the Longitude Prize was offered, when the voyages occurred, etc. Could someone with access to reference materials please provide them? -- Sapphire Wyvern 01:50, 9 August 2007 (UTC)
Could someone add information on why degrees are divided into "minutes" and "seconds"? Is there some relation to time that I am missing or is 60 simply a useful number to divide from hence a clock analogy? —Preceding unsigned comment added by 142.179.217.154 ( talk) 00:13, 8 September 2007 (UTC)
As per previous comments above, I've split out the history section and merged it with similar history sections in several other articles. This is now a single article History of longitude. -- Michael Daly 19:07, 30 October 2007 (UTC)
The following paragraph is found in the section on noting and calculating longitude.
It does not specify anything about the shape of the "Earth" it is using. Obviously it is not a sphere, but exactly what model is referred to is not specified. If someone recognizes the equations and can identify the model used, could they please state what it is? -- Michael Daly 19:13, 5 November 2007 (UTC)
Both the formula I added for a degree of longitude and the formula added by CielProfond for a degree of latitude represent old ellipsoids and are not exact. The most recent parameters for Earth's ellipsoid from IERS Conventions (2003) (Chp. 1, page 12) are an equatorial radius a = 6378136.6 m and an inverse flattening 1/f = 298.25642. The latter yields e² = 0.0066943980 using e² = 2f−f². An exact expression for the radius of curvature along a meridian (north-south) from The Math Forum is:
Multiply by 2π/360 to obtain the length of a degree of latitude at a geodetic latitude φ. At the equator (φ = 0°), this reduces to (2π/360)a(1−e²) = 110.57427 km/°. At the poles (φ = 90°), this reduces to (2π/360)a/(1−e²)1/2 = 111.69397 km/°.
As the osculating circle with this radius of curvature moves around the ellipse formed by a meridian and its anti-meridian, its center of curvature moves along the evolute of the ellipse, the astroid, a figure with four concave curves connecting four cusps aligned with the axes of the ellipse, the southern arcs and cusp being the center of curvature for northern latitudes and the north pole, respectively, and vice-versa for southern latitudes.
An exact expression for the radius of curvature along a line of latitude (east-west, but in the prime vertical, the plane perpendicular to the plane of the meridian and also perpendicular to the plane tangent to the surface of the ellipsoid) from The Math Forum is:
Multiply by (2π/360)cosφ to obtain the length of a degree of longitude. At the equator (φ = 0°), this reduces to (2π/360)a = 111.31948 km/°. At the poles, of course, this is 0 km/°.
The center of the radius of curvature in the prime vertical is always on the polar diameter, moving from the geocenter at a latitude of 0° to a point on the diameter farthest from the pole at a latitude of 90°. Both radii of curvature have the same value at the poles. These formulae for the radii of curvature also appear on pages 24–25 of Map Projections—A Working Manual by John P. Snyder (1987). — Joe Kress 04:59, 7 November 2007 (UTC)
Although most will not be interested in the exact formulae, some request them as in Google Answers (never provided). I'm added a section entitled "Degree length" encompassing most of my previous edit, without mentioning the astroid. But I am including a table for latitudes every 15° per your request. — Joe Kress ( talk) 03:36, 25 December 2007 (UTC)
In my opinion the image is too small to be useful. I would like at least for the prime meridian to be visible. (possibly a higher resolution image?) Also the longitudes shown on the map might be difficult for some to see. jay ( talk) 19:38, 29 December 2007 (UTC)
I think it would really help if the image at the top right of the article were to only show longitude (vertical lines?) instead of both vertical and horizontal. It is difficult for me to remember which (longitude or lattitude) is which (vertical or horizontal). The drawing of the earth with lines helps express the concept, but it does nothing for me to get staright in my head whether longitude is vertical or horizontal. Sam Tomato ( talk) 13:59, 29 December 2011 (UTC)
IPA would be helpful. —Preceding unsigned comment added by 81.140.57.113 ( talk) 16:38, 27 February 2008 (UTC)
As of today there is an article on every whole-numbered line of longitude with the exception of the following (all are West longitude lines): 124, 126, 127, 128, 129, 131, 132, 133, 134, 136, 137, 138, 139, 142, 143, 144, 146, 147, 148, 149, 151, 152, 153, 154, 156, 157, 158, 159, 161, 162, 163, 164, 166, 167, 168, 169, 171, 172, and 173. Backspace ( talk) 20:49, 3 February 2009 (UTC)
The last paragraph of the history section mentions that Paris has been used as a location for the prime meridian. The link from Paris takes one to the article on the city Paris. There is a Wikipedia page called Paris_Meridian. Perhaps sending the reader there would be more informative. (I had forgotten about the Paris Meridian, but today I was using some WW I French maps with two longitude scales. After some thought I remembered. The difference in the Longitude measurements makes me belive one scale used Paris and one Greenwich.) Nicodemus ( talk) —Preceding undated comment added 04:11, 2 November 2011 (UTC).
I have greatly simplified (and renamed as above) the 'Degree length' section by removing many of the comments which appear in Latitude: this article should put longitude first. The discussion of latitude and nautical mile is not appropriate to this page. There is absolutely no need to mention curvature and reduced latitude. There is also no need for any of the material in the 'Elliptic parameters' section and I have removed it: the relation between e, a, and b is enough. I have simplified the table since it is misleading at present: the relation between columns 2 and 3 is not the same as that between columns 4 and 5. Values of N are not needed. (Note that the prime vertical plane does not intersect the reference ellipsoid in a line of latitude). I could add a simple figure to this section if it is thought appropriate. Peter Mercator ( talk) 21:32, 31 December 2011 (UTC)
Gavin Menzies' 1421 book is used as a reference for the Chinese initial discovery of a longitude method. I'm not an expert, hence writing this before editing the article, but I know the book is widely discredited by historians (read any account of it other than by Menzies himself) and at any rate is popular historical fiction and not a scholarly work. I cannot find any other reference suggesting the Chinese had discovered a method for locating longitude before the Europeans, I propose the whole paragraph be deleted. 82.1.124.153 ( talk) 13:31, 26 August 2012 (UTC)
“… it is with the help of these clocks and the following methods that longitude is found. … observe exactly the time at the place from which we are making our journey. … When we have completed a journey … wait until the hand of the clock exactly touches the point of an hour and, at the same moment by means of an astrolabe … find out the time of the place we now find ourselves. … In this way I would be able to find the longitude of places, even if I was dragged off unawares across a thousand miles. … it must be a very finely made clock which does not vary with change of air.” – Regnier Gemma Frisius 1553
In an era where the relationship between the 24 hour system in tandem with the Lat/Long system organized around the Earth's rotational characteristics are disputed,it is no accident that this insight of Frisius is airbrushed out. Orion216 ( talk) 07:57, 29 October 2013 (UTC)
In the table, it would appear that the tables for latitude and longitude are transposed? Cinderella157 ( talk) 05:37, 10 November 2015 (UTC)
I believe "longitude" is also used for the location of a body on an orbit (e.g. position of a planet at a given moment).
Certainly it is also used in "
longitude of the ascending node", one of
the constants used to describe an orbit. (Which is using a different frame of reference, afaik, than the above concept.)
The lead should reflect these common generalized uses of the geometrical concept of longitude, instead of limiting the definition to "the east–west position of a point on the Earth's surface", as the article currently does.
--
BjKa (
talk)
14:20, 7 November 2018 (UTC)
The lead read:
I reworded this as:
@ Jc3s5h: reverted, saying "Misleading in spots, poor English in other spots." I'm not sure what Jc3s5h thinks is misleading or poor English, so let me explain my rationale for the changes:
To my ear, the new wording is better in every way, but I'm certainly not attached to it -- perhaps we can find some better way of improving the current clumsy text. I'd also be curious to know what exactly Jc3s5h thinks was misleading or poor English in the new phrasing. -- Macrakis ( talk) 14:46, 4 June 2020 (UTC)
The diagram of Amerigo Vespucci's observation is misleading. It leaves the impression that his early lunar distance method was based on a 3.5 degree lunar parallax. But the lunar parallax is not more than 1 degree for a full Earth diameter.
This section seems somewhat unbalanced. The first sentence states that longitude is important both for cartography and navigation, then what follows talks almost entirely about navigation. Also the time-frame is very limited. There is a long history of ancient work on longitude, from the Greek astronemers throuhgh the Muslim and Hindu worlds and back to mediaeval Europe that is not mentioned, and also much after Harrison, with electric and wireless telegraphic methods. The diagram on lunar distances is misleading - all that can really be seen, in exaggerated form, is parallax - but parallax is a source of error that has to be allowed for in the calculation, not what is primarily being measured. I suggest following the outline of the History of Longitude article, condensing it to about the same length as the current section (about 1,000 words). Comments appreciated. Kognos ( talk) 11:50, 21 September 2020 (UTC)
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level-4 vital article is rated C-class on Wikipedia's
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Are Dava Sobels' books "Longitude" (which I thought was history wrapped in a historical novel) and "A True Story...." the same book? DJ Clayworth 15:07, 20 Oct 2003 (UTC)
In the article it says that the prime meridian is the one passing through Greenwich. Is that still true? I thought the prime meridian had moved 90 feet and the line marked at Greenwich is no longer valid. Is not the prime meridian for UTC the 90 deg one in Chicago? Does ANYONE still use GMT?
Drg40 (
talk)
13:59, 13 May 2012 (UTC)
This article says longitude runs between +180° and −180°, but it does not say whether east or west is positive. I had always thought that it was standard that west is positive, never suspecting until a couple of hours ago that anyone used the other convention. Then I saw Wikipedia's list of earthquakes, which does use the opposite convention. As I stated on that article's discussion page, I once heard the head of the math department at MIT (David Vogan, who has since been succeeded as department head), speaking before about 150 undergraduates, state that it's appropriate that longitudes in Europe are negative since Europe is a cultural cesspool. No one responded that east longitudes are positive and west negative. (Nor did anyone complain about that characterization of Europe.) So I'm not the only one to think that's standard. Michael Hardy 02:35, 3 Jan 2005 (UTC).
So whoever wrote list of earthquakes had it wrong, then. Michael Hardy 03:21, 4 Jan 2005 (UTC)
WGS84 has longitude positive eastward, negative westward. Urhixidur 14:11, 2005 Jan 4 (UTC)
From a strictly mathematical point of view, our usual standard is to use a right-hand coordinate system, in which angles are measured in a counterclockwise fashion. -- Jacobolus 00:10, 15 Feb 2005 (UTC)
I am curious, however about all the fuss with clocks. Yes, clocks are great and solve the longitude problem. I have taught that. But the motion of the Moon in relation to the Sun and to the stars can be used to tell time, too. Just occurred to me that though it's a bit complicated and not quite so accurate, it might work to low accuracy, but good enough for simple navigation, say within a few degrees longitude.
Pdn 05:19, 25 Feb 2005 (UTC)
Moon/Mars picture/text problem: While the diagram of the moon and Mars shows how they would not appear to be lined up from a position to the west, it shows the Moon appearing to the east of Mars, while the text describes Mars as being to the east. Where's the error, and should this be explained? Piledhigheranddeeper ( talk) 19:04, 9 December 2008 (UTC)
I have removed the reference to shipwrecks in Western Australia, since only 5 are known of in early times: English East India Company's, Trial (1622), the Dutch East India Company's
Batavia (ship) (1629), Vergulde Draeck (1656), Zuytdorp (1712) and Zeewijk (1727). For these early wrecks I dont know to determine the role of longitude navigation errors as opposed to chart errors (uncharted reefs) and other causes. Anyway ship wrecks were occuring in many parts of the world, motivating the search for a solution. -
Op. Deo
20:18, 23 August 2005 (UTC)
The clocks were not so good, but could not the ancient mariners have measured time by the motion of the moon, at least when it's visible at the same time as the sun, so you can get the angle between the two? Pdn
Yes this is the method of Lunar Distances which was the practical competitor to Harrison's chronometer in C18. It was at first limited because the orbit of the moon was not known by ship's officers. But eventually suitable tables were produced which made it easy to measure the moons position relative to certain stars on the ecliptic and determine local time, and therefore longitude. It was then cheaper to provide ships with a set of tables and a sextant, rather than a very expensive chronometer modelled on Harrison's design, So in some ways the impact of Harrison's successful toil was limited. - Op. Deo 22:29, 23 August 2005 (UTC) Thanks. I just saw that Galileo devised a method of using the Moons of Jupiter. see [2] which says: "For Galileo, his admonition marked the beginning of a period of silence. He busied himself with such tasks as using tables of the moons of Jupiter to develop a chronometer for measuring longitude at sea. He endured his rheumatism, ..." Pdn 04:40, 24 August 2005 (UTC)
Latitude says that they are not "exactly" equal to 1 nautical mile whereas this article says that Latitude is "exactly" equal to 1 nortical mile! This seems to be to be something that needs clearing up. —Preceding unsigned comment added by 58.105.29.26 ( talk • contribs)
The 4th paragraph should be changed, both because it is factually wrong (twice) and because it contradicts the entry under "Latitude." This creates confusion and introduces uncertainty as to which is correct. The differences may seem small but I was led to this entry while trying to resolve an apparent error in the ground track of a satellite orbit simulator. The error was resolved by using the correct definition of latitude as shown by the Wikipedia entry for that parameter (as opposed to the one implied here.) Mennochio 23:38, 30 July 2006 (UTC)
I agree. I also suspect it is worth pointing to nautical miles, statute miles, and the Great Circle Distance Formula in the same discussion. As is, the formula for equivalency in one long. deg. is misleading (i.e., are degrees in radians? do I get km, really?) 71.236.220.71 16:31, 25 October 2006 (UTC)
I think the article should emphasize the primary purpose of longitude: that together with the latitude it uniquely identifies any point on the surface of Earth (or other celestial body). This is mentioned only in the third paragraph, saying
and in the link to Geographic coordinate system in the See also section. I am not sure yet how to change the article to emphasize this more, so I did not edit it. – b_jonas 21:08, 19 June 2006 (UTC)
How many miles is 15 degrees (1 timezone) of longitude? -- Homfrog Tell me a story! 00:41, 30 December 2006 (UTC)
I suggest a fork of the section ==History of the measurement of longitude== to a new article named measurement of longitude (as a starter).
The German article de:Längenproblem discusses also earlier geometric methods as well as the more curios proposals (firing cannons, injuring dogs and the like), while this article, as well as Board of Longitude and John Harrison, cover much of the same. -- Matthead discuß! O 09:04, 25 July 2007 (UTC)
There are very few dates given in this section. I wanted to know when Harrison built his various chronometers, when the Longitude Prize was offered, when the voyages occurred, etc. Could someone with access to reference materials please provide them? -- Sapphire Wyvern 01:50, 9 August 2007 (UTC)
Could someone add information on why degrees are divided into "minutes" and "seconds"? Is there some relation to time that I am missing or is 60 simply a useful number to divide from hence a clock analogy? —Preceding unsigned comment added by 142.179.217.154 ( talk) 00:13, 8 September 2007 (UTC)
As per previous comments above, I've split out the history section and merged it with similar history sections in several other articles. This is now a single article History of longitude. -- Michael Daly 19:07, 30 October 2007 (UTC)
The following paragraph is found in the section on noting and calculating longitude.
It does not specify anything about the shape of the "Earth" it is using. Obviously it is not a sphere, but exactly what model is referred to is not specified. If someone recognizes the equations and can identify the model used, could they please state what it is? -- Michael Daly 19:13, 5 November 2007 (UTC)
Both the formula I added for a degree of longitude and the formula added by CielProfond for a degree of latitude represent old ellipsoids and are not exact. The most recent parameters for Earth's ellipsoid from IERS Conventions (2003) (Chp. 1, page 12) are an equatorial radius a = 6378136.6 m and an inverse flattening 1/f = 298.25642. The latter yields e² = 0.0066943980 using e² = 2f−f². An exact expression for the radius of curvature along a meridian (north-south) from The Math Forum is:
Multiply by 2π/360 to obtain the length of a degree of latitude at a geodetic latitude φ. At the equator (φ = 0°), this reduces to (2π/360)a(1−e²) = 110.57427 km/°. At the poles (φ = 90°), this reduces to (2π/360)a/(1−e²)1/2 = 111.69397 km/°.
As the osculating circle with this radius of curvature moves around the ellipse formed by a meridian and its anti-meridian, its center of curvature moves along the evolute of the ellipse, the astroid, a figure with four concave curves connecting four cusps aligned with the axes of the ellipse, the southern arcs and cusp being the center of curvature for northern latitudes and the north pole, respectively, and vice-versa for southern latitudes.
An exact expression for the radius of curvature along a line of latitude (east-west, but in the prime vertical, the plane perpendicular to the plane of the meridian and also perpendicular to the plane tangent to the surface of the ellipsoid) from The Math Forum is:
Multiply by (2π/360)cosφ to obtain the length of a degree of longitude. At the equator (φ = 0°), this reduces to (2π/360)a = 111.31948 km/°. At the poles, of course, this is 0 km/°.
The center of the radius of curvature in the prime vertical is always on the polar diameter, moving from the geocenter at a latitude of 0° to a point on the diameter farthest from the pole at a latitude of 90°. Both radii of curvature have the same value at the poles. These formulae for the radii of curvature also appear on pages 24–25 of Map Projections—A Working Manual by John P. Snyder (1987). — Joe Kress 04:59, 7 November 2007 (UTC)
Although most will not be interested in the exact formulae, some request them as in Google Answers (never provided). I'm added a section entitled "Degree length" encompassing most of my previous edit, without mentioning the astroid. But I am including a table for latitudes every 15° per your request. — Joe Kress ( talk) 03:36, 25 December 2007 (UTC)
In my opinion the image is too small to be useful. I would like at least for the prime meridian to be visible. (possibly a higher resolution image?) Also the longitudes shown on the map might be difficult for some to see. jay ( talk) 19:38, 29 December 2007 (UTC)
I think it would really help if the image at the top right of the article were to only show longitude (vertical lines?) instead of both vertical and horizontal. It is difficult for me to remember which (longitude or lattitude) is which (vertical or horizontal). The drawing of the earth with lines helps express the concept, but it does nothing for me to get staright in my head whether longitude is vertical or horizontal. Sam Tomato ( talk) 13:59, 29 December 2011 (UTC)
IPA would be helpful. —Preceding unsigned comment added by 81.140.57.113 ( talk) 16:38, 27 February 2008 (UTC)
As of today there is an article on every whole-numbered line of longitude with the exception of the following (all are West longitude lines): 124, 126, 127, 128, 129, 131, 132, 133, 134, 136, 137, 138, 139, 142, 143, 144, 146, 147, 148, 149, 151, 152, 153, 154, 156, 157, 158, 159, 161, 162, 163, 164, 166, 167, 168, 169, 171, 172, and 173. Backspace ( talk) 20:49, 3 February 2009 (UTC)
The last paragraph of the history section mentions that Paris has been used as a location for the prime meridian. The link from Paris takes one to the article on the city Paris. There is a Wikipedia page called Paris_Meridian. Perhaps sending the reader there would be more informative. (I had forgotten about the Paris Meridian, but today I was using some WW I French maps with two longitude scales. After some thought I remembered. The difference in the Longitude measurements makes me belive one scale used Paris and one Greenwich.) Nicodemus ( talk) —Preceding undated comment added 04:11, 2 November 2011 (UTC).
I have greatly simplified (and renamed as above) the 'Degree length' section by removing many of the comments which appear in Latitude: this article should put longitude first. The discussion of latitude and nautical mile is not appropriate to this page. There is absolutely no need to mention curvature and reduced latitude. There is also no need for any of the material in the 'Elliptic parameters' section and I have removed it: the relation between e, a, and b is enough. I have simplified the table since it is misleading at present: the relation between columns 2 and 3 is not the same as that between columns 4 and 5. Values of N are not needed. (Note that the prime vertical plane does not intersect the reference ellipsoid in a line of latitude). I could add a simple figure to this section if it is thought appropriate. Peter Mercator ( talk) 21:32, 31 December 2011 (UTC)
Gavin Menzies' 1421 book is used as a reference for the Chinese initial discovery of a longitude method. I'm not an expert, hence writing this before editing the article, but I know the book is widely discredited by historians (read any account of it other than by Menzies himself) and at any rate is popular historical fiction and not a scholarly work. I cannot find any other reference suggesting the Chinese had discovered a method for locating longitude before the Europeans, I propose the whole paragraph be deleted. 82.1.124.153 ( talk) 13:31, 26 August 2012 (UTC)
“… it is with the help of these clocks and the following methods that longitude is found. … observe exactly the time at the place from which we are making our journey. … When we have completed a journey … wait until the hand of the clock exactly touches the point of an hour and, at the same moment by means of an astrolabe … find out the time of the place we now find ourselves. … In this way I would be able to find the longitude of places, even if I was dragged off unawares across a thousand miles. … it must be a very finely made clock which does not vary with change of air.” – Regnier Gemma Frisius 1553
In an era where the relationship between the 24 hour system in tandem with the Lat/Long system organized around the Earth's rotational characteristics are disputed,it is no accident that this insight of Frisius is airbrushed out. Orion216 ( talk) 07:57, 29 October 2013 (UTC)
In the table, it would appear that the tables for latitude and longitude are transposed? Cinderella157 ( talk) 05:37, 10 November 2015 (UTC)
I believe "longitude" is also used for the location of a body on an orbit (e.g. position of a planet at a given moment).
Certainly it is also used in "
longitude of the ascending node", one of
the constants used to describe an orbit. (Which is using a different frame of reference, afaik, than the above concept.)
The lead should reflect these common generalized uses of the geometrical concept of longitude, instead of limiting the definition to "the east–west position of a point on the Earth's surface", as the article currently does.
--
BjKa (
talk)
14:20, 7 November 2018 (UTC)
The lead read:
I reworded this as:
@ Jc3s5h: reverted, saying "Misleading in spots, poor English in other spots." I'm not sure what Jc3s5h thinks is misleading or poor English, so let me explain my rationale for the changes:
To my ear, the new wording is better in every way, but I'm certainly not attached to it -- perhaps we can find some better way of improving the current clumsy text. I'd also be curious to know what exactly Jc3s5h thinks was misleading or poor English in the new phrasing. -- Macrakis ( talk) 14:46, 4 June 2020 (UTC)
The diagram of Amerigo Vespucci's observation is misleading. It leaves the impression that his early lunar distance method was based on a 3.5 degree lunar parallax. But the lunar parallax is not more than 1 degree for a full Earth diameter.
This section seems somewhat unbalanced. The first sentence states that longitude is important both for cartography and navigation, then what follows talks almost entirely about navigation. Also the time-frame is very limited. There is a long history of ancient work on longitude, from the Greek astronemers throuhgh the Muslim and Hindu worlds and back to mediaeval Europe that is not mentioned, and also much after Harrison, with electric and wireless telegraphic methods. The diagram on lunar distances is misleading - all that can really be seen, in exaggerated form, is parallax - but parallax is a source of error that has to be allowed for in the calculation, not what is primarily being measured. I suggest following the outline of the History of Longitude article, condensing it to about the same length as the current section (about 1,000 words). Comments appreciated. Kognos ( talk) 11:50, 21 September 2020 (UTC)