Abstract: Ground based GPS technique is rapidly growing in remote sensing water vapor content in the atmosphere. In this paper, the problem of extracting water vapor content information from GPS data is examined. A new approach, namely as piecewise linear method has been proposed in the estimation of precipitable water vapor through Hong Kong DGPS station observations. Considering no meteorological measurements, a simple interpolated method weighted by distance is developed to perform the interpolation using the meteorological observations around Hong Kong DGPS station. To evaluate the attainable accuracy of water vapor content sensed by GPS, radiosonde data, which are collected locally by Hong Kong Observatory, are used to calculate the precipitable water vapor. One month results of precipitable water vapor from both ground based GPS technique and radiosonde method exhibit very good agreement within 1 mm~2 mm.