DEVELOPMENT OF A TIME-DEPENDENT 3-PARAMETER HELMERT DATUM TRANSFORMATION MODEL: A CASE STUDY FOR MALAYSIA

Abstract. This paper aims to develop a time-dependent 3-parameter Helmert datum transformation model for Malaysia as a proposed solution to the current non-geocentric issue of the Geocentric Datum of Malaysia 2000 (GDM2000). Methodologically, the datum transformation models is categorised into three parts; firstly, the time-dependent aspect of the datum transformation model is determined using the tectonic motion velocities computed from linear least squares regression of the long-term time series of MyRTKnet stations positions from year December 2004 to 2014; whereby the station positions are obtained from high-precision daily double-difference processing of MyRTKnet and IGS stations via Bernese 5.0. Secondly, the 3 Helmert translation-only parameters, are derived between the original GDM2000 and GDM2000@2013 – the new datum coordinates which refers to ITRF2008 at epoch 3/7/2013 – via Bernese 5.0 software. Thirdly, a distortion model is computed in order to minimise the coordinate residuals between the ‘processed’ and ‘transformed’ new datum. The datum transformation model is then validated to determine the reliability of the model. The validation results show that the datum transformation model is within centimetre-level accuracy, i.e., below 3 cm, over Malaysia for forward transformations to year 2014 and 2015. Therefore, this study anticipates that it will contribute as a feasible solution for the GDM2000 issue with consideration of the core concern: the complex tectonic motion of Malaysia.