ELEVATION MEASUREMENTS OF BENCHMARKSBESIDE THE RURAL ROADALONGTHE WESTCOAST OF CHUMPHON PROVINCE BY GNSS METHOD

Abstract

Elevations of objects or ground points above mean sea level are determined by GNSS network method instead of conventional leveling, after the Development of Precise Geoid Model of Thailand. The project area is about 20 kilometers far from the first order of benchmark determined by Royal Thai Survey Department. Seventeen permanent benchmarks are constructed beside the rural road along the west coast of Chumphon Province by spacing about 500 meters. Measuring geographic coordinates of temporary points nearby seventeen benchmarks by static method, observing simultaneously at least 1 hours (by technique of relative positioning).Compute geoid undulation from TGM2017 and compute elevations by GNSS method. Measuring elevations of benchmarks by the method of three wires closed circuit differential leveling by level instrument. Measuring elevations by GNSS method is equal or better than 12 mm√Kor Order 3 (leveling). Elevations above mean sea level by GNSS method is faster than leveling method for this project area.