The GPS constellations are now more than 30 years old. The first satellite, launched on Feb. 22, 1978, was in the Block I constellation. It was designated SVN 1/ PRN 4 and remained operational for 21.9 months. A total of 11 Block I satellites were launched from 1978 to 1985; one of the 11 failed to attain orbit. Since 1989, all satellites launched are designated as Block II. .
As many readers know, the horizontal control stations in the NAD 83 system were readjusted and the results published in February 2007. It’s a national readjustment; all readjustment stations are in the same coordinate system.
The first two articles in this series (POB August 2007 and October 2007) explained how to solve for geoid heights, N, using Stokes’ equation. The gravity anomaly in that equation, Δg, has many different forms.
Geodesy is not a dead science as some people think. GPS satellites are geodetic satellites. Their orbits have origins at the center of mass of the earth, and are tracked from stations located on a geodetic datum or reference frame.
Q: When I use my prism/antenna poles, I’ve noticed that some are easier to hold still than others. My dealer told me this is because the “bubble sensitivity” of one is higher than the other, with the more-difficult-to-hold pole having higher sensitivity.
This column includes updates on the Global Navigation Satellite System (GNSS) scene, as well as an update on U.S. Global Positioning System (GPS) satellites. It has been announced in various publications that both China and India are making plans to create their own GPS equivalents.