In urban area, surface and subsurface are crowded with existing structures. Hence the de-signs in geotechnical engineering projects are controlled by serviceability rather than stability require-ments. Control of ground deformation is crucial. Accordingly, it is important to precisely monitor the ground deformation around the construction site. Typically, settlement beacon has been utilized to meas-ure the ground deformation. Recently, the rapid development in electronic technology, digital image pro-cessing and computing power enables 3D image scanning to become available for measuring the ground deformation profile. Regarding obtaining the ground deformation profile, the 3D scanning work has an advantage, whereas its accuracy is somewhat limited because it does not directly measure the ground de-formation. In this study, we developed a conditional merging technique to combine the traditional method and the 3D scanning method. Synthetic ground deformation profile was generated to validate the proposed technique. It is found that the ground deformation measurement error can be reduced significantly via the conditional merging technique.