PRECISION AND ACCURACY OF GPS TIME TRANSFER

The precision of time transfer over intercontinental distances by the GPS common-view method reaches 3-4 ns for a single 13 min measurement, and decreases to 2 ns when averaging several measurements over a peri od of one day. Such precision can only be achieved by using measured i onospheric delays, precise ephemerides, and a consistent set of statio n coordinates. The accuracy of GPS time transfer can be estimated by u sing three intercontinental links encircling the Earth to establish a closure condition. It is found that the accuracy is also at the level of a few ns, and mainly depends upon the set of ephemerides which is u sed for the satellites.