On Thu 2022-07-28T17:01:31-0700 Paul Eggert hath writ:
Thanks. Sorry to have induced you to go to all that work in digging up historical measurements of the Paris Meridian, as the current datum doesn't depend on the exact value. It's simpler, I think, to remove that longitude from the comments as that will save us the trouble of picking and citing a longitude. Done in the attached patch.
Not a lot of work. The Paris/Greenwich offset was a topic of concern from the 18th century. For most of the story see https://doi.org/10.1017/S0007087413000988
-# the Paris Meridian (2° 20' 14.03" E); the former yields 07:06:30.1333..., -# the latter 07:06:29.333..., and for now guess the former, +# the Paris Meridian; for now guess the former and round the exact +# 07:06:30.1333... to 07:06:30.13 as the legal spec used 66 2/3 ms precision.
This is still bothersome because of that Paris longitude. A value of 14.03 for the arc seconds is a time value of 9m 20.935 s. No recent measurement had a value that large. Using either 20.93 or 20.932 for the Paris Observatory the offset of this zone in 1906 would be 7:06:30.06 -- Steve Allen <sla@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m