Atmospheric water vapor is highly variable in both space and time

and the accuracy of Interferometric synthetic aperture radar（InSAR） is limited by the effect of the atmosphere

especially the atmospheric water vapor on repeat-pass InSAR measurements.In order to assess the competence of the MODIS（the Moderate-Resolution Imaging Spectroradiometer） near-infrared water vapor retrieval and gound meteorological model estimation for correcting atmospheric effects on InSAR measurements

coincident observations obtained from Global Positioning System（GPS） measurements at five sites in Fangshan Beijng over a month period（April 2004） are used for time series and spatial comparisons.Comparisons of PWV between MODIS and GPS show that their correlation coefficients are high although MODIS appeared to overestimate PWV against GPS;The wet components of tropospheric delay estimated using two empirical models from the ground meteorological data obtained at the GPS sites show low correlation coefficients with the results derived from GPS.