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Far more logical and sensible solution than blaming it on Americans, as one 
individual posted at the base of the article.  Petty.

The coupling between the meridian and the wall of the measuring equipment is 
fairly obvious.  Time the objects as they cross the meridian with your 
equipment.

What wasn't obvious was that the wall shifted as each new set of measuring 
equipment came into play.  Odd that there was no attempt to align the walls 
to each other.   It would have been child's play for a surveyor to place the 
new measuring equipment such that it was co-planar with the old.  Instead, 
the wall was allowed to shift in longitude, albeit not significantly.  Of 
course, it still had to be aligned to the meridian it was installed on.

Thanks Douglas.

Best Regards
Brad




-----Original Message-----
From: navlist@fer3.com [mailto:navlist@fer3.com] On Behalf Of douglas.denny@btopenworld.com
Sent: Wednesday, October 21, 2009 5:26 AM
To: NavList@fer3.com
Subject: [NavList 10208] Re: At the centre of time


I should have continued with this quote too
from:-
http://gpsinformation.net/main/greenwich.htm
--------

"The Airy Transit's position

Comparing the longitude of the Airy Transit in the system available in 1936 to 
the longitude determined with space techniques gives a difference.

Using Ordnance Survey Level 1 Transformation

  Airy Transit, GB36 =      N 51 28 38.265    E 00 00 00.418
  Airy Transit, ETRF89 =    N 51 28 40.1247   W 00 00 05.3101

  X 3980637.8044  Y - 102.4779  Z 4966897.8318

The difference in longitude between the two systems at the Airy Transit is 
102.478 metres. Therefore the International Reference Meridian is 102.5 
metres east of the Airy Transit at Greenwich. As the IRM is tied to the 
definition of time the real reference meridian to be used for the Millennium 
is the IRM which, as shown above, is about 100 metres east of the Greenwich 
Meridian."

--------------

Douglas Denny.
Chichester.  England.




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