Geoscience Reference
In-Depth Information
Fig. 2
Post-seismic and co-seismic motions in Peninsular Malaysia (Omar and Mohamed
2010
)
2 Status of Geocentric Datum of Malaysia (GDM2000)
Traditionally, there were two existing local geodetic reference systems in
Malaysia, namely the Malayan Revised Triangulation 1948 (MRT48) for Penin-
sular Malaysia and Borneo Triangulation System 1968 (BT68) for Sabah and
Sarawak. The reference ellipsoid for the MRT48 and BT68 are Modified Everest
(Kertau) and Modified Everest (Timbalai), respectively (Department Survey and
Mapping (DSMM)
2009
). However, their origins are not explicitly defined and in
practice could be many hundreds of metres away from the geocentre (Kadir et al.
2003
). On 26 August 2003, the GDM2000 was officially launched nationwide as a
national geocentric datum to replace the MRT48 and BT68. It was realized
through a set of GPS observations at seventeen (17) Malaysia Active GPS System
(MASS) stations and eleven (11) IGS stations, from 1999 to 2002. All the MASS
coordinates were defined on the most precise available reference frame at that time
i.e. the ITRF2000, based on the Geodetic Reference System (GRS80) ellipsoid.
In 2002, DSMM established a new Continuously Operating Reference Station
(CORS) network known as the Malaysian Real-Time Kinematic GNSS Network
(MyRTKnet) with 78 reference stations nationwide, to improve the MASS stations
and support the generation of network-based positioning solutions. However, on
26 December 2004, these stations underwent land displacements in the range of
1.5-17 cm and orientation predominantly in the south-west direction due to the
co-seismic motion from the Aceh earthquake (Department Survey and Mapping
(DSMM)
2009
). Similarly, the results from Nias and Bengkulu earthquakes
indicated land displacements of between 1-6.5 cm and 1-3 cm respectively, also
in the south-west direction (Department Survey and Mapping (DSMM)
2009
).
Therefore, a revision of the GDM2000 was carried out.
Thus far, the revision of GDM2000 had been conducted in epoch 2006 and
2009
which
were
labelled
as
GDM2000
(2006)
and
GDM2000
(2009),
