Hi Ian, Exactly so, and it would be interesting to see what dials there were on such a whole number list. But the snag in all this though is that the definitions have all been changed. The arrival of satellite technology brought with it a global redefinition of the whole earth's ellipsoid and in 1999 the International Reference Meridian (IRM) was decided. This is fixed but not fixed relative to a point on the earth! It currently passes something like 5.31 arcseconds east of Airy's meridian or 102.5 metres (336.3 feet) at the latitude of the Royal Observatory, Greenwich. But since 1999 and as a consequence of continental drift and plate tectonics, the IRM has shifted a few centimetres West back towards the Airy meridian. Airy will eventually be right (again!). That must surely be a time for REAL celebration?
In the UK WGS84 latitudes and longitudes are changing at about 2.5 cm per year in a north-easterly direction. In 1989, the International Reference Meridian passed an estimated 102.478 m to the east of the Airy Transit Circle at Greenwich. There’s more about this here: http://www.thegreenwichmeridian.org/tgm/articles.php?article=7 So, members of the ‘Zero Meridian Club’ are chasers after ephemera. They will need to keep coming back every few years simply to catch up... Patrick From: Ian Maddocks Sent: Wednesday, April 30, 2014 6:14 PM To: Douglas Bateman ; Sundial list Subject: RE: The GPS zero meridian club Hi Doug Well there's already a very similar web site confluence.org/ This is for people trying to stand on points of exact degrees intersecting (according to WGS84) I have stood on two such points 54.0000 N 2.0000 W (on a lonely bit of moorland above Skipton, UK. It's very boggy , be careful ;-) ) and 52 N 5 E (Just next to a roundabout near Utrecht in the Netherlands). Trying to think back to my browsing of the site I don't recall any dial connections but then most of these confluences do lie the middle of nowhere . A more pertinent question might be what dials are on whole number lat / long lines (and why) Good luck with the membership drive! Ian Maddocks Chester, UK --- Original Message --- From: "Douglas Bateman" <[email protected]> Sent: 30 April 2014 17:37 To: "Sundial list" <[email protected]> Subject: The GPS zero meridian club This is a new club consisting, so far, of two members: Frank King and myself. After the successful British Sundial Society conference, the Sunday morning was allocated to tours of the Greenwich Observatory. Quite independently, Frank and I had the intention of location the WGS84 meridian, some 90m east of the Greenwich brass strip. Frank had an eTrex tracker and an app on his mobile phone, and I had an Axxera GPS tracker linked to my iPad. The images, if the system will let them through, show 0º 0' 0". Anyone else willing to join this new exclusive club? Plenty of places to straddle the line between the north pole and the south pole. Doug (and Frank) -------------------------------------------------------------------------------- --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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