Limitation of Edge Location

Triaxial test is an important test in civil engineering. Soil specimen deformation needs edge location in triaxial test. Edge location accuracy has the limitation. The accuracy limitation is greater than 0.2 pixels by mathematical reasoning. In order to obtain high resolution of edge location, an improved test method is adopted to solve the limitation of edge location. According to the new test method, we take advantage of subpixel corner detection algorithm to locate the edge. Test results show that the accuracy is improved by five times than the old method. After long-term test, the radial accuracy steadily reaches 0.02 pixels and the axial accuracy steadily reaches 0.05 pixels