STRATEGIES FOR SPATIAL AND TEMPORAL EXTRAPOLATION AND INTERPOLATION OF WET DELAY

The excess radio-path delay due to the atmospheric water vapor, the we t delay, can be derived from water vapor radiometer (WVR) measurements . WVR data used for external calibration of space geodetic measurement s are not always acquired in the directions of the space geodetic sign al sources, thus extrapolation and interpolation methods for the wet d elay are needed. We evaluate three different methods using approximate ly 10 days of WVR measurements. Two methods, the gradient method and t urbulence method, use the directional information in the data, while t he third method used is linear regression in time regardless of the di rection of the observations. The turbulence method yielded at least 10 % less RMS estimation error than the errors from the other two methods .