Archive for February 12th, 2006

Prime Meridian

The Prime Meridian, the one through Greenwich, England, doesn’t line up in Google Earth. As you can see, the meridian in this projection is east of the observatory, by about 100 meters. The reason:
This is not a mistake on Google’s part. The developers of Google Earth (originally known as Keyhole) chose to support the same coordinate system as that used by GPS technology known as WGS-84 World Geodetic System.

Click here for a technical explanation of all this. Basically, the earth isn’t a smooth, regular sphere, and GPS is so accurate, something had to give. So they shifted the Prime Meridian. And there’s also the contribution of continental drift….

Google Earth (it’s FREE), if you haven’t yet explored it, is fascinating—searchable satellite photos of THE WORLD! Add places to your personal list, or send them out to the Google community.

Trivia: the GPS system uses 25 satellites, each with two atomic clocks. Bob Burns turns 80 today (Happy Birthday, Bob!). Jack Finlayson has come through his surgeries okay.