My OperaGreenwich Wrap up
Monday, February 7, 2011 3:13:34 PM
I did a bit more digging on the prime meridian issue when I got home. Keyhole, which was the code name for Google Earth had a blog about it. Unfortunately it did not really give any background. In the google blog it just says that the best least squares fit to the earths surface thay could achieve was the prime meridian where it is today. I will add some background commentary hereo. The earth is not a perfect sphere so as positioning technology improved, maps which are based on a perfect sphere (or on a flat earth for pancakians out there) were not accurate. A mathematical technique called "Least Squares Fit" was used to model the existing maps to the earth for the GPS technology.
However, something is still missing The prime meridian, and all latitude and longitudes, are just arbitrary points, so even with using WGS84 datum, it was should still be possible to do a least squares fit, and then adjust everything to the prime meridian. Then after a bit more digging, Wiki gave up some clues.
My summary of the Wiki article is that John Hopkins University in Maryland developed the first Doppler based Sat Nav system. They had a ground station as part of this system and it's surveyed coordinates became the reference point for their mapping system. They went on to survey North America using some point on campus as starting point. The result of this is the farther away from John Hopkins you are, the greater the error. In reality JHU should now be the prime meridian.
Cheers
Off to Maryland to calibrate my GPS Bryan
However, something is still missing The prime meridian, and all latitude and longitudes, are just arbitrary points, so even with using WGS84 datum, it was should still be possible to do a least squares fit, and then adjust everything to the prime meridian. Then after a bit more digging, Wiki gave up some clues.
My summary of the Wiki article is that John Hopkins University in Maryland developed the first Doppler based Sat Nav system. They had a ground station as part of this system and it's surveyed coordinates became the reference point for their mapping system. They went on to survey North America using some point on campus as starting point. The result of this is the farther away from John Hopkins you are, the greater the error. In reality JHU should now be the prime meridian.
Cheers
Off to Maryland to calibrate my GPS Bryan
