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mepvic
20th March 2006, 12:02 PM
Was in Greenwich in the UK last year at the observatory and armed with my trusty hand held Garmin, found that the line in the ground marking 0,0,0 is, acording to my GPS, about 5.35" to the west of what my GPS showed as 0,0,0.

Typed in N51 28 40.4, E 0,0,0 into Google earth and shows the same result. 0,0,0 is about 100M or so to the east of the Greenwich line. You can see the line on Google earth directly in front of the roof hip to the left of the tree.

Can anyone explain the difference??

arthurking83
20th March 2006, 02:32 PM
Continental drift (??)

The reason for all those Datums!

If you compare AGD66, which was measured in 1966 (as the name implies) to the current GDA94, you will find the same grid reference about 200m to the south west(for GDA94).

As the Prime Meridian was surveyed about 150years ago(??), that would explain some of it.

I don't know the rate at which the UK is affected by continental drift, but Australia, and surrounding islands move NE by about 7cm/year.

There would also be an accuracy issue involved with the GPS, and the measurements taken 150 years ago.....etc!


:confused: