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SIMONS ET AL.: GPS MEASUREMENTS IN S.E. ASIA TO REFINE SUNDALAND MOTION X - 7
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Figure 6. GPS Velocities w.r.t. Sundaland. Shown are the residual velocities w.r.t to the updated Sundaland pole for
the 28 sites used (open dots with black vectors).
differences between the estimated and the ITRF-2000 velocities for
IGS sites used in the mapping are typically below 1 mm/yr for the
horizontal and a few mm/yr for the vertical components. The IGS
sites that were mapped along with the S.E. Asia network, are also
within these differences. For stations BAKO, NTUS, PIMO and
DARW the velocities computed in this analysis are more accurate
than in ITRF-2000, since they are based on longer time series.
Based upon the results in Table 6, taking into account the velocity
differences for IGS sites closest to the S.E. Asia network as well as
the internal accuracy of this network, it can be concluded that the
S.E. Asia computed velocities have absolute accuracies, which are
in agreement with the formal errors (1-) obtained in the final step
in this section. The horizontal velocity vectors have (1-) errors
range from about 0.3 mm/yr for the permanent stations to 0.5 to
2.5 mm/yr (depending on the number of observations/time elapsed)
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for the episodically observed sites. A number of new sites have
larger errors because they were only observed twice in the past year
(mainly Sulawesi sites and 1 THAICA site in South-Thailand). The
velocity vectors along with their (3-, for more clearness) uncertainties
are shown in Fig. 4. The velocity field is available from the
first author upon request and it can be used as a reference solution,
or to connect to other regional network solutions.
4. Sundaland Motion and deformation
4.1. Pole estimation
In this paper, we present an updated Sundaland pole in ITRF-
2000 derived from the velocity field obtained by processing GPS
data described in the previous section. This pole was carefully es-
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