OSV (On-Site Visualization) monitoring is a system that measures information which is shared visually in real time at site. It was introduced by Akutagawa in 2006 and has been effectively applied at various construction sites since then. The basic function of the OSV is to show changes in deformation, pressure, inclination, etc. of structures as well as ground movement using colored lights, namely blue, yellow and red through light-emitting converter and LED lights electrically. Through these

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... evious site experiences, the OSV performance has been reassessed; it has been recognized that a major problem with the system is the cost of the number of electrically driven OSV devices needed to cover many locations for a more effective OSV operation. More simple mechanical monitoring devices have now been devised which do not require electricity and are sufficient and reliable enough to monitor structure and ground movement. These low-cost OSV devices have been introduced at the Bai Chay Road project in Vietnam as the first trial of low-cost OSV on an overseas project. Finally we propose a basic strategy for evaluating the performance of the OSV system and improving construction safety, utilizing low-cost OSV.