Tropospheric water vapor variation monitoring based on low-cost GNSS

Current methodologies for calculating precipitable water vapor (PWV) from global navigation satellite system (GNSS) predominantly rely on ground-based observatories, which cannot be densely deployed considering the cost constraints. The emergence of low-cost dual-frequency receivers has made it possible to intensively monitor tropospheric water vapor changes, and in order to further improve the accuracy of detecting PWV by low-cost devices, in this paper, we employ the precise point positioning (PPP) method to compare the accuracy of the zenith tropospheric delay (ZTD) in single-system (GPS) and multi-system modes (GPS+BDS+GLONASS+Galileo) via an economical dual-frequency receiver (u-blox), authenticate the PWV data accuracy derived from budget-friendly equipment against the fifth major global reanalysis (ERA5), and analyze the change process of PWV before and after rainfall. The experimental outcomes illustrate that the economical u-blox module attains ZTD estimations on par with those from pricier geodetic receivers, the multi-system fusion is more stable and more accurate than a single-system, and the ZTD accuracy is improved in terms of mean absolute error (MAE) and root mean square error (RMSE) by 28% and 30%, respectively. Nonetheless, when contrasted with ERA5-PWV, the PWV values obtained from the cost-effective device was 2.81 mm and 3.72 mm at MAE and RMSE, respectively. In comparison, the equivalent metrics for the high-end receiver stand at 2.31 mm and 3.04 mm, indicating a marginally inferior accuracy of PWV inversion with the economical device relative to its high-end counterpart. Despite this, during periods of rainfall, the low-cost apparatus proficiently delineates the correlation between PWV and actual precipitation, adequately satisfying the exigencies of meteorological pursuits such as weather prediction. These insights show that low-cost consumer-grade GNSS receivers have huge application potential in large-scale and intensive monitoring of tropospheric water vapor variation.