Abstract
A GPS displacement measurement system has been widely used for monitoring the slope stability. Tall trees and other obstacles on the slope often cause a disturbance to the signals transmitted from the satellites and a degradation of the measurement accuracy. It is an important issue to be overcome for applying GPS to monitoring the deformation of slopes.
In this paper, "the mask method" developed by the authors is adopted for improving the measurement accuracy under overhead obstacles. It is proven that the method was effective for monitoring a slope at a tunnel entrance during tunnel construction. The measured results of three dimensional displacements are discussed for assessing the slope stability.
