An Appropriate GPS Technology for Landslide Monitoring at East-West Highway, Perak, Malaysia
 Khamarrul A.R Email: kamaz_80@yahoo.co.uk Wan Aziz W.A Email: Waziz@fksg.utm.my Faculty of Geoinformation Science & Engineering University Technology Malaysia Skudai 81310, Johore
1. Introduction
The assessment of landslide behavior is usually undertaken by means of monitoring scheme. Usually, the measurement of superficial displacement is the simplest way to observe the history of a landslide and to analyse the kinematics of the movement. In all cases, measurements have to be made efficiently in terms of time, manpower and budget. In the past, a variety of surveying techniques have been used to detect the superficial movements of unstable area (Mikkelsen, 1996). For examples, tapes and wire devices have been used to measure changes in distance between points or crack walls (Gulla et al., 1988). Levels, theodolites, Electronic Distance Measurement (EDM), and total station measurements provide both the coordinates and changes of target, control points and landslide features (Ashkenazi et al., 1980). In addition, aerial or terrestrial photogrammetry provides point coordinates, contour maps and cross-section of the landslides. Photogrammetry compilation enables a quantitative analysis of the change in slope morphology and also the determination of the movement vectors (Oka, 1998). A comprehensive summary of the main methods and their precisions is shown in Table: 1. Table:1 Overview of methods used in measuring surface displacement and their precision a (Mikkelsen, 1996)  a Note: 1ppm means one part per million or 1additional millimetre per kilometre of measured line. Nowadays, the Global Positioning System (GPS) has been fully operational. The GPS equipment is more reliable, cheaper, faster, and easier to use compared to conventional instruments. New hardwares, field procedures and softwares have also been developed to assist users in data collection and processing purposes. Thus, the GPS equipment has become more progressive and used for a wide range of monitoring applications. This paper therefore highlights the performance of GPS technology in landslide monitoring encompassing a specific large-scale area.
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