การปรับปรุงแบบจำลองยีออยด์ท้องถิ่นในประเทศไทยโดยลีสท์สแควร์คอลโลเคชั่นสำหรับการหาความสูงของภูมิประเทศ

Abstract

This research aims to improve a local geoid model in Thailand using least-squares collocation with parameters. The model was computed by integrating the local gravimetric geoid model, THAI17G, and GNSS/leveling co-points of the Royal Thai Survey Department, referred to Ko Lak national vertical datum. The 399 co-points were divided into 299 points to calculate conversion or correction surface between THAI17G and Ko Lak vertical datum and 100 points for geoid accuracy testing. The improved geoid model was obtained by adding the conversion surface to THAI17G and then compared with the geoid model using 2 method: (1) polynomial interpolation and (2) leastsquares collocation. In addition, it was compared with THAI17G and EGM2008. The assessments were done in 5 separated areas, having different topographic. Each study area influenced the accuracy of the improved geoid model for each method of the calculation. The study results show that the geoid model using the least-squares collocation with parameters method can improve geoid heights' accuracy the most. The model has a standard deviation of ± 3.9cm, representing 34 percent improved accuracy.