Each entry made records the actual WGS84 coordinates
displayed on a GPSr device that is positioned at a physical marker which is
marking the Prime Meridian. The point is to demonstrate, pursuant to the
preceding conversation here, that the choice of datum when reporting Lat and
Long is relevant. Frequently the WGS84 reading will show other than 0°
0.000" E/W because different datums (data ?) than WGS84 have been used when
placing the physical markers. This is not a scientific survey of course, nor can
it be used in any way to deduce errors elsewhere. It is simply for
illustration and one of the larger collections of such "in the field" reports of
such deviations that I am aware of. It adds additional information to what Roger
found from Google Earth.
--- In BoundaryPoint@yahoogroups.com, "Hugh Wallis"
<hugh@o...> wrote:
>
> Take a look here where the difference
between WGS84 and various other
> "observations" is documented at
various locations along the prime meridian
>
> http://tinyurl.com/76jv4
>
>
> _____
>
> From:
BoundaryPoint@yahoogroups.com [mailto:BoundaryPoint@yahoogroups.com]
>
On Behalf Of Roger McCutcheon
> Sent: Tuesday, January 03, 2006 6:20
AM
> To: BoundaryPoint@yahoogroups.com
> Subject: Re:
[BoundaryPoint] Four pointer
>
>
> I went to maximum
magnification on Google Earth and found that it did indeed
> show zero
longitude as being about three quarters of the way to the far side
> of
Black Heath Avenue, to the east of the Zero Meridian in the Royal
>
Observatory, so then I went to the Prime Meridian site and found that
"the
> zero meridian on the WSG84 datum, which is about 100 metres to
the east of
> the line marked at Greenwich, is an average of the various
continental
> movements", so we need not worry: someone is paying
attention! Roger
>
McCutcheon.