Wouldn't that be "un pied dans chaque hemisphere" in France? I visited the Greenwich observatory a number of years ago, but it was after 5 PM and all of the exhibits were closed for the day. So we only saw the repeater clock and the meridian line. One interesting fact: A GPS receiver will not agree with the line set into the concrete about where zero degrees of longitude is located. The GPS prime meridian is somewhere nearby, within the park, but not at the marked line.
An explanation for this (that I found at the time) is that the line in the ground at the observatory is defined as zero longitude in whatever geodetic ellipsoid and datum the British were using at the time. The GPS zero longitude line is at zero in WGS84. Apparently WGS84 is defined to agree with the older British datum in longitude *at the equator*, but the two ellipsoids use different models of the earth's axis and so the two zero-longitude meridians do not agree at Greenwich's latitude of ~50 N. Google found this more recent article: http://www.thegreenwichmeridian.org/tgm/articles.php?article=7 that has more interesting (and more detailed) information about the difference in the prime meridian definitions. Dave On Tuesday, 5 July 2016, jimlux <jim...@earthlink.net> wrote: > > One must, of course, take a picture with one foot in each hemisphere. > (Unless, you would follow the French, in which case, the Paris meridian is > the only true meridian, and then you'd have one meter in each > hemisphere...<grin> > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.