An Appropriate GPS Technology for Landslide Monitoring at East-West Highway, Perak, Malaysia
3. The Experiments
The performance of the GPS technique in measuring ground displacements has been tested in the active landslide phenomena. This landslide area is located at the East-West Highway, namely km22 and km26, Eastern Perak, Gerik, Malaysia.  Figure: 2 - Location of Gerik Landslide, East-West Highway, (a) km22 and (b) km26 The East-West Highway is the only route that connected the district of Gerik, Perak to Jeli, Kelantan- see Figure: 2. The Gerik landslide is one of eight locations, which has been declared and identified by Malaysian government as a high-risk landslide activity area. The National Landslide Research Center (NASEC) has also classified this area as a high-risk landslide activity in the ROM format scale. The GPS preliminary surveys for landslide study were made in February 2003. Eleven baselines ranging from 62m to 3200m in length were observed by using dual frequency GPS receivers, Trimble 4800. The static technique has been applied to set up the reference network in the landslide areas. Figure: 3 (a) and (b) shows the control network establishment and satellite-receiver geometry during the observation, respectively.  Figure: 3- (a) Control network for static observation; (b) Example of planning the geometry of available satellite in Gerik (Eastern Perak, Malaysia) on February 26, 2003. The rapid static and RTK GPS positioning techniques were used in the landslide monitoring scheme. In our experiment, two control points have been established at each landslide areas, namely BM and GK 1 for km22 test site, and JL 1 and JL 2 for km26 test site. In order to form a complete deformation network, thirteen and fifteen monitoring stations have also been monumented at sites km22 and km26, respectively - see Figure: 4 (a) and (b). Figure 5 (a) and (b) show the rapid static observation at the landslide areas. The static and rapid static GPS data were carried out in post-processed mode using Trimble Geomatics Office (TGO) software while the GPS kinematic data were processed in real time mode.  Figure: 4 - Monitoring network for km22 (a) and km26 (b).  Figure: 5 (a) and (b) Rapid static GPS observation for km22 and km26, respectively. |