Determination and evaluation of orthometric height derived from Malaysian Continuously Operating Reference Station of MyRTKnet / Mohd Zainee Zainal

Traditional levelling in determination of heighting is time consuming, labor intensive and costly. With the advent of Global Positioning System (GPS) technology coordinate in 3D can be obtained with reasonable accuracy. This study investigates the capability of GPS as a tool of obtaining heights value. Static and Real-Time Kinematic with Virtual Reference Station (RTK VRS) technique of GPS observation is chosen for height determination. For static observation mode, absolute and relative GPS heighting concepts are investigated. Only absolute GPS heighting concept is investigated in RTK VRS mode. The study area comprises of Negeri Sembilan and Melaka in Peninsular Malaysia. In this study, it is shown that static mode of GPS
observation utilizing the absolute GPS heighting concept can achieve heighting difference between observed and known height in the range of -0.131 m and 0.045 m. The Root Mean Square (RMS) value for static mode using absolute GPS heighting concept is ±0.079 m. Static mode using relative GPS heighting concept gives mean relative accuracy of 2.6 ppm. In this study, the duration of GPS observation for point positioning is also investigated. For 5 hours of GPS observation, it is capable of determining height in the first-order accuracy points with less than 1.1 km (0.010. m). Using RTK VRS method of observation, the range of height difference is between -0.005 m and -0.202 m. The results also show that there are no significant differences between broadcast and precise ephemeris. From this research, it is possible to do GPS heighting in study area.