wwp@yahoogroups.com:
Re: Previous Coordinates Question
Landis 2007-Aug-12 16:21:00
At 15:46 +0000 8/12/2007, Geoff Mather wrote:
>Before you get too carried away with accuracy, its worth taking a
>look at the Greenwich Observatory, and deciding for yourself how
>accurate the Lat/Long is. The Latitude is clearly out by 5.4 seconds
>when you turn on the Grid view! The Prime Meridian passes to the East
>of its actual location ...
Yes, that certainly does look strange. Perhaps Google should have
accurately named the line they call the Prime Meridian as the
International Reference Meridian. The 0 Longitude line in Google
Earth is based on the WGS 84 datum which is what is used on the
majority of GPS receivers (it's the native system for GPS) and this
model puts the Greenwich Meridian Line 102.4779 meters to the west of
the IRM 0. There's a really good explanation of this at the
Flamsteed Astronomy Society: http://www.flamsteed.info/faswgs84.htm
The Prep Server is currently down. We'll see about getting it open
again for editing coordinates on all previous events and hopefully
everyone can take a look at their contributions and offer any
corrections.
-Landis