Application of Fitting of Moving Quadric Surface to Height Anomaly Fitting in the Band-Shaped Area

Global Navigation Satellite System (GNSS), which can provide high-precision coordinates in the global geodetic framework, is able to replace most geodetic surveying, but it is difficult to replace conventional leveling surveying due to height anomaly. The Fitting of Moving Quadric Surface (FMQS) is based on the known points in the circular region with the center of the point to be fitted and a specific radius. In this paper, the method of FMQS is used to fit the height anomaly of Nanjing section of Yangtze River and the downstream, and the results show that the fitting accuracy of the 226 points evenly distributed along the river is 1.86 cm; At the same time, the fitting of GNSS height determination using this set of data can replace the fourth order leveling that the leveling line more than 3.46 km at 95.5% confidence interval. Benchmarks data collected in the field show that the difference between the height of National Vertical Datum 1985 obtained by geodetic height fitting with Jiangsu CORS and the height of National Vertical Datum 1985 obtained by third order leveling is within 2 cm.