GPS phase-delay measurement: technique for the calibration and analysis in millimetre-wave radio propagation studies

Observation of phase delay from GPS satellites, followed by signal and data processing allows the quantity of water vapour in the atmosphere to be continuously monitored. At millimetre-wavelengths, water vapour has significant impact on radiowave propagation, along with rain, cloud and oxygen. Comparisons are presented of integrated precipitable water vapour measured by GPS with a co-sited radiometer and with radiosonde measurements from a nearby site. Data are also presented in which the liquid water (cloud and rain) attenuation is separated from radiometer predicted total attenuation using the measurement of water vapour by GPS. The GPS technique thus represents a new tool to study radiowave propagation, and aids in the calibration of radiometers operating in frequency bands that are sensitive to water vapour