The impact of different international terrestrial reference frames (ITRFs) on positioning and mapping in Malaysia

Abstract

In Malaysia, Geocentric Datum of Malaysia 2000 (GDM2000) is connected to the International Terrestrial Reference Frame 2000 (ITRF2000). In comparison with the previous models, ITRF2014 represents a significant improvement in datum definition and realization. Nevertheless, the improvement causes a frame difference between ITRF2000, ITRF2008 and ITRF2014. Due to earthquakes that hit Sumatra region of Indonesia in the years 2004, 2005 and 2007 followed by post-seismic and co-seismic activities, Malaysia no longer lies on a stable continent. The movement on tectonic plate caused a shifting in geodetic datum of Malaysia to become non-geocentric. Thus, this factor gives impacts on positioning and mapping in Malaysia particularly in the realm of cadastral. Therefore, to measure the effect, the coordinates for positioning and mapping based on different International Terrestrial Reference Frames were analysed. To achieve the aim, this study is categorized into three phases. In the first phase, Global Positioning System (GPS) data was processed with respect to different reference frames (ITRF2000, ITRF2008 and ITRF2014) by Precise Point Positioning (PPP) Waypoint software. The result derived from the first phase was then be used in the next phase, where the coordinate was analysed based on different reference frames. In the third phase, the reliability of coordinate with different ITRFs was assessed specifically for cadastral purposes. In order to analyse the coordinates, a point at helipad of Universiti Teknologi Malaysia (UTM) was observed by using GPS static technique, and the data was processed differently according to the frames by PPP. The coordinates processed were used as a base station for fast static GPS observation. To process the data, Trimble Total Control (TTC) software was used resulting in three different coordinates of each point observed. The coordinates were assessed with respect to the existing Cassini-Soldner geocentric coordinates and coordinates derived from network-based Real-Time Kinematic (RTK) observation. The results show that ITRF2014 has small value of standard deviations with the mean of 0.0010, 0.0003 and 0.0020 m for latitude, longitude and height for point positioning. Whereas for mapping, the differences between coordinates from PA 40225—ITRF2000, PA 40225—ITRF2008 and PA 40225—ITRF2014 in general range from −0.277 to −0.209 m for northing and from 0.424 to 0.515 m for easting. In conclusion, GDM2000 has to be revised frequently with respect to the latest version of ITRF in order to give a better positional accuracy, and a fix geocentric mapping datum needs to be opted for cadastral integrated purposes in Malaysia.