A STUDY ON SOLID EARTH TIDES

Abstract

In many geodetic analyses, it is important to consider the effect of solid earth tide on the J instantaneous position of a station and its subsequent influence on the computation and interpretation of time series of coordinates as well as related data products. In this research work, effect and temporal variations in position of the IGS (International Global Navigational Satellite Systems [GNSS] Service) station at 1-lyderahad, due to earth tide, has been carried out. Surface tidal displacement of the station has been computed on daily basis for a month based on the concept of gravity. Further, mean daily coordinates of the station has been computed using static precise point positioning (PPP) method for a month. Results show that the station undergoes temporal displacements and its coordinates varies continuously within a day and all the days in the month. The maximum range in vertical displacement of the station has been found to be .4 about 48 cm in a day, over the month and those along the North and East directions is respectively 8 cm and 14 cm. The ranges in variation in the geodetic latitude, longitude and height of the station have been found to be 1.23 cm, 2.73 cm and 3.52 cm respectively. Further, it has been found that the tidal oscillations follow some periodicity, and thus need to be studied independently for all stations. By Precise Point Positioning the variation in the position at a particular station is observed for a month of November 2013. The deformation is observed in all the three directions at lOS Hydcrabad and Pune station for the month and they follow the similar deforniation pattern which is due to Solid Earth Tides. Further, the variation is computed at both the stations in a particular - day at 1-minute interval in all the three directions. The displacements are observed simultaneously and seem to follow a definite pattern between LOS Hyderabad and Pune station. It is observed that there is a definite time lag between both the stations. Therefore it is possible to calculate the propagation directions and speed of the Solid Earth tides. The result comes out to be that first the high tide reaches the 105 Hyderahad station and then Pune station with a time lag of 20 minutes and the propagation velocity of around 425 rn/s. Further the variation along baseline is observed by computing six baselines between four stations and when the effect is studied simultaneously for all baselines it follows a definite pattern. Therefore this shows that how the Solid Earth tides continuously affecting the instantaneous site position of any station.