Comparison of Elevation in a straight line from Leveling with Level and Global Navigation Satellite Systems

Abstract

Accurate elevation determination is essential in civil engineering for ensuring the structural integrity of constructed facilities. Traditional optical leveling, while highly precise, requires transferring elevation values from existing benchmarks, which can be time-consuming when the benchmarks are located far from the project area. Recent advances in Global Navigation Satellite Systems (GNSS) technology-especially using static surveying techniques with post-processing and geoid correction-have enabled the possibility of determining elevation data more efficiently. This study evaluates the accuracy of GNSS-based elevation measurements compared with conventional third-order leveling methods, focusing on a straight-line transect of 2,201 meters at the Agricultural Technology Research Institute, Rajamangala University of Technology Lanna. The GNSS survey was conducted using the static method, with observed data post-processed and converted from ellipsoidal to orthometric height using the Thailand Geoid Model 2017 (TGM2017). The optical leveling was performed to third-order standards using both aluminum and Invar leveling rods. Results show that the elevation difference obtained from GNSS measurements deviated by only 6 millimeters from the optical leveling result, which falls within the allowable error margin for third-order leveling standards. The findings confirm that GNSS, when used with a validated geoid model, is a viable alternative for elevation determination in engineering applications under the Thai vertical datum, particularly for establishing local control benchmarks with reduced fieldwork time and cost.