Rusli Othman

The Geocentric Datum of Malaysia: Preliminary Assessment and Implications

The reliability of the national geocentric datum must be assessed regularly to maintain high geospatial accuracy in terms of consistency with respect to the global datum, i.e. International Terrestrial Reference Frame (ITRF). This can be accomplished by considering the spatial and temporal variations caused by plate tectonic movements. This study aims to assess the reliability of Geocentric Datum of Malaysia (GDM2000) by analysing the datum shifts via the displacements of the Malaysian Real Time Kinematic Network (MyRTKnet) stations caused by tectonic movements as well as the displacements induced by reference frame effects. A significant land displacement up to 17 and 30 cm in north and east components were found respectively, due to local active fault and the cumulative plate tectonic motion. The implications of a non-geocentric datum are also discussed.

Spatial and Seasonal Ionospheric Error Growth in DGPS Measurement: A Case Study in Malaysia

This paper tackles the Equatorial ionosphere and its effects on Differential Global Positioning System (DGPS) error growth over Malaysia by using a network of GPS Continuously Operating Reference Stations (CORS). Seasonal variation of ionospheric delay has been examined and findings show that the effect of spatial variation of ionospheric errors in DGPS is very significant during the equinoctial seasons. Furthermore, a DGPS regression model was developed and tested during the solar maximum year in 2013 by using internet-based DGPS. The results show that the model is capable of estimating DGPS positional errors for distances of user to reference station less than 680 km.

Deformation detection for ISKANDARnet

Abstract Tragedies and disasters in the past have shown the threats that are associated with large construction projects. A timely identification of precursory movements may save lives and minimise collateral damage. An advanced global positioning system (GPS) continuously operating reference station network known as ISKANDARnet is operated continuously to detect deformations in Iskandar, State of Johor, Malaysia. In this study, three GPS continuously operating reference stations from the ISKANDARnet were used as the object stations along four nearby international GNSS service stations (NTUS, XMIS, COCO and PIMO) used as reference stations. The GPS data were streamed and processed by a GPS processing software module, Bernese processing engine. A deformation analysis module was developed using the MATLAB programming language to carry out continuous two-epoch analyses. The development also involves the implementation of the iteratively weighted similarity transformation method and a final S-transformation to analyse the GPS data. By applying these techniques, unstable object points were identified within the monitoring network and accurate displacement vectors were computed. The time-based variation of the displacements was shown in this paper. Test results showed that the system performed satisfactorily.