No abstract

No abstract

A simple method for estimating geocentre motion is presented and applied to the seasonal variation in air mass and moisture stored on the Earth's land surface. Data given by Rosenhead and by van Hylckama indicates that the motion attains a maximum of 4.3 mm near the equinoxes and a minimum of 1.5 mm near the solstices, that is, about an order smaller than the point-co-ordination accuracy modern high-precision geodesy aims to achieve.

The estimated median accuracy of 194 single-day determinations of the earth's angular position in space is 0.7 millisecond (0.01 arc second). Comparison with classical astronomical results gives agreement to about the expected 2-millisecond uncertainty of the 5-day averages obtained by the Bureau International de l'Heure. Little evidence for very rapid variations in the earth's rotation is present in the data.