Application of GPS phase delay measurements in radio science and atmospheric studies

Observation of phase delay from GPS satellites, combined with advanced software processing, allows the quantity of water vapour in the atmosphere to be continuously monitored. This paper reports on four years of measurements and analytical studies directed towards establishing the accuracy of the technique. It also examines the role of horizontal gradients of wet delay in determining accuracy, and evaluates the potential of extending the technique to measurement of radio refractivity gradients using a tomographic inversion technique.