I had heard a rumor that the Greenwich Meridian was not where it was supposed to be any more, so I decided to investigate... 
Sure enough, it showed W 0-00'-05.27". My Prism Girl and I headed east (admittedly without a survey grade GPS), and set up the iPhone in "static" mode (we stood still for 5 minutes), until the instrument settled down:
This was about 300' east of where the hundreds of tourists apparently thought they were "on the line". The rumor was, that there was a rubbish bin marking the real spot, but no such luck...just an intersection of two worn paths in the grass. What's a surveyor to do? Follow and trust the evidence?
The tour guide at the Royal Observatory said he'd heard about that but said he thought that the clocks that the GPS system use were wrong.:-D
I have been to the equator, but not Greenwich. Of course there is the issue of astronomic longitude versus geodetic longitude. 
But I would think that at least in Greenwich they would have made geodetic=astronomic.
Rule number 1. Words must always be read with the meaning at the time of writing...
Unfortunately the nice treatise includes wrong parameters for GRS80. See Dr Milbert's post on GRS80 parameters to this site.
Thread was
GRS 80 not merely geometric
Discussion in 'https://surveyorconnect.com/threads/grs-80-not-merely-geometric.280193/forums/gnss-geodesy.22/&apos ;">GNSS & Geodesy' started by https://surveyorconnect.com/threads/grs-80-not-merely-geometric.280193/members/geeoddmike.677/&apos ;">GeeOddMike, https://surveyorconnect.com/threads/grs-80-not-merely-geometric.280193/threads/grs-80-not-merely-geometric.280193/&apos ;">Sep 19, 2014.
Once you find out that the Greenwich Meridian is in the wrong place you can't go wrong heading down to the river and spending the rest of the day drinking away your disappointment at either The Cutty Sark or The Trafalger.
James Fleming, post: 335323, member: 136 wrote: Once you find out that the Greenwich Meridian is in the wrong place you can't go wrong heading down to the river and spending the rest of the day drinking away your disappointment at either The Cutty Sark or The Trafalger.
We chose the Cutty Sark
OMG! If the gospel is wrong, how wrong must all of its subvariations be around the world. Perhaps St. Louis is really in Illinois or Memphis is in Arkansas.
Holy Cow, post: 335335, member: 50 wrote: OMG! If the gospel is wrong, how wrong must all of its subvariations be around the world. Perhaps St. Louis is really in Illinois or Memphis is in Arkansas.
Well, when I was learning grid/ground transformations, a survey I'd done in Vermont did show up in Nova Scotia, but I don't think it had anything to do with GPS timing.:-D