3 ms·
More interesting is regular continental drift is a thing as well. Up to several centimeters per year depending on where you are. The Greenwich meridian is no lo
by jillesvangurp 4y ago
More interesting is regular continental drift is a thing as well. Up to several centimeters per year depending on where you are. The Greenwich meridian is no longer running through the dotted line they have there, for example. It's about a hundred meters away from there. That's a couple of hundred years of continental drift and some other corrections.
- eesmith 4y agohttps://en.wikipedia.org/wiki/Prime_meridian_(Greenwich) https://en.wikipedia.org/wiki/Prime_meridian_(Greenwich) > The actual reason for the discrepancy is that the difference between precise GNSS coordinates and astronomically determined coordinates everywhere remains a localized gravity effect due to vertical deflection; thus, no systematic rotation of global longitudes occurred between the former astronomical system and the current geodetic system. Cites https://link.springer.com/article/10.1007/s00190-015-0844-y https://link.springer.com/article/10.1007/s00190-015-0844-y which breaks down the reason for the approximately 102 m difference ("In Sects. 2 and 3, the authors show that the deflection of the vertical (DoV) can account for the entire longitude shift at Greenwich.") and some of the alternatives. For example: > Crustal motion from plate tectonics is also much too small to explain the observed longitude difference. Britain and most of Europe are moving toward the northeast at about 3 cm/year (a longitude change of 0.1 arc-second/century) with respect to the WGS 84 terrestrial coordinate frame (Altamimi et al. 2012). The accumulated effect relative to other monitoring stations amounts to only a few meters since its designation as prime meridian in 1884.