Investigation of MODIS mission capability in tropospheric delay estimation for precise point positioning

Tropospheric delay is always considered as one of the factors limiting the accuracy of GPS. In this paper, the three-dimensional ray tracing technique is proposed to calculate the tropospheric delay. The ability of the MODIS mission to calculate the tropospheric delay is also examined. For this purpose, an area in central Europe was selected and a MODIS acquisition on 2008/08/01 was studied. In addition, the radiosonde observations as well as ERA-Interim meteorological data were used to evaluate the obtained results. After applying corrections to the MODIS acquisition, the three-dimensional ray tracing method was implemented at the location of a GPS station using all three types of data to extract the tropospheric delay. The RMS of difference between the results of MODIS and results of radiosonde and ERA-Interim data was 1.11 and 0.89 cm respectively. Then, precise point positioning was done using the Bernese software and tropospheric correction from MODIS, radiosonde and ERA-Interim data and compared with precise coordinate of station. The accuracy of position with MODIS tropospheric correction is less than ones corrected with radiosonde and ERA-Interim tropospheric data. The results show the low efficiency of MODIS data for tropospheric correction of GPS observations compare to radiosonde and ERA-Interim data.