Talk:Royal Observatory, Greenwich

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WikiProject Time assessment rating comment[edit]

Narrowly a B class.

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Yamara 15:56, 22 March 2008 (UTC)

Rated Mid Importance; could be High, but that distinction might better belong to the article on the meridian itself. --Yamara 16:50, 7 May 2008 (UTC)


I believe the observatory moved to Cambridge in 1988 not 1990.


I believe there is a significant ommision in this article relating to the foundation of the Observatory, that being the driving force and leading role played by Sir Jonas Moore. It was Moore who, in his role as Suveyor General at the Ordnance Office, proposed to establish a Royal Observatory in 1674, and, in Flamsteed's own words, persuaded King James II that the Observatory might be built with Flamsteed employed in it. It was then the Ordnance Office that was responsible for building the Observatory, with Moore providing the key instruments and equipment for the observatory at his own personal cost. Moore coninued to have much influence over the work carried out at the Observatory until his death in 1679. The role played by Moore in establishing the Observatory was acknowledged in an inscription near the door, and on a plate within the grounds. See Sir Jonas Moore; Oxford Dictionary of National Biography . I will therefore add a reference to Moore in the main article under the History section. —Preceding unsigned comment added by BishopOdo (talkcontribs) 12:44, 4 February 2009 (UTC)

Page move[edit]

This page should be moved to Royal Observatory, Greenwich, as this is now the correct name of the institution that remains (with a redirect of course).

Unless there is dissent, I will move the page later this week. Rnt20 13:13, 15 November 2005 (UTC)

Its fine where it is. Royal Greenwich Observatory is a far more likely search phrase than anything with a comma in it. MRSC 17:37, 15 November 2005 (UTC)
Yes, a move seems like a good idea, seeing as that is the correct, current name. Redirects will take care of anyone searching using other names. Vclaw 23:20, 17 November 2005 (UTC)

One of the nature 50[edit]

Nature [1] says there is 5 errors in this article (as of december 14). Who can spot them?--Rayc 21:00, 14 December 2005 (UTC)

Not errors, but inaccuracies, which could be "factual errors, critical omissions and misleading statements", as correctly noted in the flag. Several could be critical omissions of events between 1675 and WWII. These could include discoveries made at the RGO. One event is that Greenwich Mean Time was first transmitted to the rest of the island of Great Britain in 1847 (see time zone#history). Most Astronomers Royal are not mentioned. It was noted above that the RGO moved from Herstmonceux to Cambridge in 1988, not 1990. Possibly the move required several years, as did the move from Greenwich to Herstmonceux, so this may be a misleading statement rather than an error. The article fails to note that the Prime Meridian is no longer aligned with the brass strip, but is now about 100 meters east of it according to modern reference systems, such as the World Geodetic System and the International Terrestrial Reference Frame. — Joe Kress 06:38, 15 December 2005 (UTC)

Maybe someone should let Nature know that anyone can edit this. Including them. If they don't like it, they can just go ahead and fix it. Unlike with Britannica. ;) Kafziel 20:16, 15 December 2005 (UTC)

Nature does know that, but why would they do so? Besides, I wish all journals did this, we'd get so much great advise on what needs fixing. -- user:zanimum
Why would they do so? I dunno... why do WE? Kafziel 21:19, 22 December 2005 (UTC)
'cause were crazies who can't resist sharing information, & don't like kids enough to teach. Trekphiler 10:13, 6 January 2007 (UTC)

Errors ID'd by Nature, to correct[edit]

The results of what exactly Nature suggested should be corrected is out... italicize each bullet point once you make the correction. -- user:zanimum

  • ‘The last time that all departments of the RGO were at Greenwich was before World War II. Many departments were evacuated along with the rest of London to the countryside (Abinger, Bradford, and Bath) in 1939.’ – in fact, Magnetic & Meteorological Dept moved to Abinger in 1924 after the arrival of the railway at Greenwich which affected readings. Then in WWII many of the instruments were put into storage for their safe keeping, with work at Greenwich scaled back to the bare minimum.
  • 'The castle now houses the International Study Centre …' – Herstmonceux Science Centre is housed in the Observatory buildings next to the castle, on the castle grounds, not in the castle itself.
User:Nunh-huh took care of this-- 21:25, 22 December 2005 (UTC)
  • ‘built as a workplace for the Astronomer Royal’ - not really, it was built to provide data for navigators, the AR was appointed to use the observatory as a means of creating that data.
I took a stab at this one. I'm still not crazy about the structure of the introduction, because the first sentence is stunted and now the paragraph seems to talk more about the Astronomer Royal than about the observatory itself, but at least it specifies that the position was created for the building, and not the other way around.

Kafziel 03:33, 4 January 2006 (UTC)

Looking further, the John Flamsteed article seems to be at odds with this: "On March 4, 1675 he was appointed by royal warrant "The King's Astronomical Observator" — the first British Astronomer Royal, with an allowance of £100 a year. In June 1675, another royal warrant provided for the founding of the Royal Greenwich Observatory, and Flamsteed laid the foundation stone in August." So that article appears to be saying that the observatory was built for the Astronomer Royal. Hmmm. Kafziel 14:27, 4 January 2006 (UTC)
  • ‘the Prime Meridian, to which longitude refers, went through the observatory’ suggests the Prime Meridian existed before the Observatory, when in fact it is a creation of the observatory.
User:Nunh-huh took care of this one too.  ALKIVARRadioactive.svg 06:38, 23 December 2005 (UTC)
  • The meridian line in the courtyard is marked by a stainless steel strip now, not brass.
User:Nunh-huh took care of this-- 21:25, 22 December 2005 (UTC)


Why is it, if I search Royal Observatory, I don't get a redirect here? Trekphiler 10:18, 6 January 2007 (UTC)

That is a possiblility, if most people who type "Royal Observatory" are looking for this royal observatory, instead of the others on that disambiguation page. Of course, the dab would then be at the top of this page. — Joe Kress 09:26, 8 January 2007 (UTC)


Surely by definition the coordinates of the observatory is 0.00000 W. Oliver Kerr (talk) 14:26, 8 May 2008 (UTC)

It depends on how you define those coordinates. According to resolution 2 of the 1884 International Meridian Conference the "initial meridian", later called the Prime Meridian, was the meridian passing through Airy's transit circle. (This immediately alienated the reference meridian used by the Ordnance Survey, Great Britain's mapping service, which passed through Bradley's transit circle, 19 feet west of Airy's transit circle.) At the time, its coordinates could only be measured astronomically, by reference to the local vertical, which is the direction of a plumb line. Furthermore, the best method of measuring the longitudes of other observatories was to send a time signal via telegraph from the Royal Observatory, then measure its received time astronomically relative to the local vertical of the remote observatory. Local verticals are all perpendicular to mean sea level (the geoid), which undulates above and below a simple ellipsoid of revolution by as much as a hundred meters, causing most of these local verticals, when extended down into the Earth, to bypass the rotational axis of the Earth by hundreds of meters. Later, these local verticals were systematized relative to several local reference datums, ellipsoids whose surfaces approximate mean sea level over limited regions of Earth's continents.
To reduce this variation of hundreds of meters, since 1989 the International Terrestrial Reference System (ITRS) has defined the IERS Reference Meridian (IRM) as the weighted least squares average of the reference meridians of hundreds of observatories around the world, none of them the Royal Observatory. The coordinates of all these observatories are determined via the reception of time signals from satellites, which can only sense the center of mass of the Earth, not any local vertical. Their reference meridians were required to be continuous with the meridians adopted by the Bureau International de l'Heure (BIH) in 1984 (no sudden offset). These were a gradual refinement of the reference meridians of stations within TRANSIT, the first geodetic satellite system, which measured coordinates via doppler shifts of signals transmitted by the satellites. Its initial meridian was the surveyed meridian on the North American Datum of 1927 (NAD27) of the laboratory which developed the system for the U. S. Navy, the Applied Physics Laboratory of Johns Hopkins University in Howard County, Maryland.
The astronomical coordinates of Airy's transit circle relative to its local vertical were 51° 28' 38"N, 0° 0' 0". When its coordinates were measured by TRANSIT in 1969, they were found to be 51° 28' 41.51"N, 0° 0' 5.92"W. This apparent longitude shift of a few arcseconds was the direct consequence of TRANSIT's reference meridian being determined elsewhere than at the Royal Observatory. The coordinates listed in the article were shifted slightly by further refinements to 51° 28' 40.12"N, 0° 0' 5.31"W. These are the coordinates of Airy's transit circle in WGS84, the coordinate system used by the satellite Global Positioning System, used by virtually all navigation receivers. WGS84 is the coordinate system required for any geographic location in a Wikipedia article according to Wikipedia:WikiProject Geographical coordinates. — Joe Kress (talk) 08:11, 9 May 2008 (UTC)

Datums or data?[edit]

The plural of datum is of course data. However I think it may be confusing to say data, and I imagine it was deliberately written that way; there's also a parallel with e.g. mediums vs media. Nevertheless, it did grind with me a little, and if somehow it could be recast to get rid of the plural altogether, that might be better? e.g. "Around the world several other places had a local datum".... something like that?

No big deal. SimonTrew (talk) 21:28, 16 April 2009 (UTC)

Au contraire — in the geodesy community (figure of the earth, cartography) the plural of datum, which see, is always datums, never data. — Joe Kress (talk) 21:53, 16 April 2009 (UTC)
The difficulty, Joe, is that it jars with those who are not in that community (with "data" specifically it also works the other way that it has pretty much become singular, and from time to time I even see perversions like datae, as if it were fourth declension). As I implied, I can quite accept it is the norm, just as nobody but a pedant writes penides or clitorides or octopdes (OK they're Greek) and as such I don't have a problem with that, but in a general article (as I see this one) rather than a very specific technical one I wonder if to try to avoid the issue with rewording might be better? I suppose my gist is, if it made me take a step backwards, who knows the plurals etc, it's going to do that for other people too.
What do you think? SimonTrew (talk) 23:36, 16 April 2009 (UTC)
Wikipedia is an encyclopedia whose purpose is to educate, not to pander to readers' biases. I suggest that a footnote be added to "datums" stating "In geodesy the plural of datum is datums, not data. See Datums by the United States Geological Survey."
Well I roughly agree with you there but to educate you have to explain. I am in rough agreement with you and I don't hthink "datums" is wrong: it you say it's right I accept that, but to an intellegent but un-knowledgeable reader it is wrong; assume maximum intelligence, minimum knowledge. Though I understands your gist for a footnote, I wonder if that is the best solution: seems to me with minor rewordinf you could just keep it as "datum" and avoid the problem, unless (which I can't see to be the case) it's deliberately introduced to teach the plural.
As I say I have no problem with the plural as such English can do what it likes and anyway (per my analogy with media/mediums) it forms what Fowler called a useful distinction; I jsut wonder whether in its specific habitat here it's confusing or distracting.
Best wishes SimonTrew (talk) 06:35, 17 April 2009 (UTC)
The paragraph containing "datums" includes "oblate spheroid" and "International Terrestrial Reference Frame", which are certainly technical, not general, terms. The gist of the paragraph is that a single datum has replaced multiple datums. Stating "around the world several other places had a local datum" belittles those datums and does not emphasize that multiplicity. Wikilinking the term is the usual way to explain an unusual term in Wikipedia. It would take two or three sentences to explain a surveying "datum". The Random House Dictionary of the English Language and Webster's Third New International Dictionary both state that the plural of "datum" for the surveying sense used here, a "reference from which positions are measured", is "datums". They state that the plural "data" is only used for "detailed information". Given these statements by major dictionaries, Wikipedia would be irresponsible if it did not give the plural for this sense. — Joe Kress (talk) 04:37, 20 April 2009 (UTC)

Number of 0.00000?[edit]

This might be a good section to add with this question. How many places have the location of a zero meridian? When were they used also? I know the GPS readings have one, two for the observatories at Greenwich, and another for the observatory in Paris. John W. Nicholson (talk) 17:47, 18 February 2013 (UTC)

On the meridian or not?[edit]

I notice that the COORD tag for the observatory is being placed 5.31 seconds west of the prime meridian. This is a bit surprising. Does anyone know why? Face-smile.svg-- (talk) 13:24, 24 March 2014 (UTC)

A paper by Seago and Seidelmann presented at the 23rd AAS/AIAA Space Flight Mechanics Meeting held February 10–14, 2013, Kauai, Hawaii explains why the center of the Airy transit is no longer at 0° longitude. This is available for free access from the company that created the software that was used in Seago & Seidelmann's calculation. The site is, look for the title "The Mean-Solar-Time Origin of Universal Time and UTC". Jc3s5h (talk) 21:59, 24 March 2014 (UTC)