Assessment of the accuracy and precision of MyRTKnet real-time services

Abstract

From a network of ninety-six (96) Continuously Operating Reference Stations (CORS), the Department of Survey and Mapping Malaysia (DSMM) has developed a reliable real-time data streaming service known as the Malaysia Real-Time Kinematic GNSS Network (MyRTKnet). MyRTKnet is now operating on Leica SpiderNet system that is configured to provide coordinate to users in Geocentric Datum of Malaysia 2000 (GDM2000). As the name implied, GDM2000 is a geocentric datum for Malaysia, developed based upon the International Terrestrial Reference Frame (ITRF) 2000 or ITRF2000. One could argue that the quality of coordinates provided by MyRTKnet are less optimal as the latest realisation of ITRF at present is ITRF2014. This study aims to investigate the accuracy and precision of the resultant coordinates from MyRTKnet real-time services through a comparison with the control-quality coordinates from a network of post-processed data at some independent points for positioning purpose. Meanwhile for mapping purpose, the coordinates from Network Real-Time Kinematic (NRTK) at selected Cadastral Reference Marks (CRM) points were compared with their known values. The results show that the observed points in ITRF2000 move approximately 37 cm away from the points in ITRF2014 due to the constant movement of Sundaland Block. Meanwhile for the assessment of NRTK technique, there is no significant displacement for coordinates in ITRF2000 but ITRF2014 with the values of 4.4 and 39.8 cm at KDOJ point, respectively. The discrepancy in ITRF2014 could be due to the improper datum transformation procedure. For mapping, NRTK technique is still not reliable to be adopted for determination of boundaries based on the results derived as the vector displacements for two (5.5 cm and 8.1 cm) out of three CRM exceed the allowable limit (5 cm). In conclusion, it is worth noting that, NRTK technique adopted for positioning should addressed a proper datum transformation process (ITRF2014 to ITRF2000) to improve quality of data meanwhile for mapping works, the NRTK technique is still unreliable to be implemented.