Research on application of GNSS in vertical control survey

摘要

The vertical control net's accuracy has been studied by using the binomial fitting method under different carrier signals of GPS, GLONASS, BEIDOU, in order to provide reference for production practice. The experiment area is in Shenyang Hunnan Road, about 15km length, including 15 elevation control points. The vertical control points have been observed by third-order closed leveling route. The data of 15 points' normal heights have been gotten. The vertical control points have been observed by GNSS static measurement. The data of 15 points' geodetic heights have been gotten. The mixed connection method of point and side has been adopted in GNSS elevation control net. The process included four periods, every period was 50 minutes. The geodetic heights have been calculated by GNSSADJ software. Four schemes have been adopted as adjustment conditions including GPS dual band (L1 and L2), GPS single frequency (L1), dual satellites (L1 and B1) and three satellites (L1, GLONASS, B1). The seven known points of distributed in the region have been used in height fitting. The eight unknown points' normal heights have been calculated by using the quadratic surface fitting formula. The elevation's differences of unknown points between height fitting result and third-order leveling result have been calculated. According to the elevation difference, the standard deviations of four groups' normal heights have been calculated. The experiment results are followed: The standard deviation of GPS dual frequency was 4.59 mm, GPS single frequency was 5.38 mm, dual satellites was 4.86 mm, three satellites was 3.99 mm. Based on the fitting results of GNSS elevation analysis, observation in the same condition, three satellites' precision was higher than dual satellites', dual satellites' accuracy was higher than single satellite's, GPS dual band accuracy was higher than GPS single band's.