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Surface is generally represented as a group of points. For the surface deformation monitoring process, the positions of a group of selected points are surveyed at two or several time instances. Then, the displacements and velocities could be computed. Most frequently, these points are signalized and remain fixed. However, the signalization process is not always easy, and the potential change of the reference system can cause difficulties in the deformation analysis. In this study, a deformation analysis system is developed. This system includes a total station based automated surface surveying module, and the analysis module.
The current system includes a Leica TM1100 electronic theodolite and a WILD DIOR3002S electronic distance measuring instrument. The operation is controlled from a connected personal computer with a program written with QBasic and GSI commands.
Field surveys were performed on October 10th, 1997 and February 13th, 1998. A laser gun based measuring system is also used at the same time. After coordinate transformation and data interpolation, the results are compared in two cases: (1) Total station 1998 versus laser gun 1998. (2) Total station 1997 versus total station 1998. The average differences of elevation are -0.243m and 1.063m, and the standard deviations are 5.215m and 2.127m. Error sources include the reference points error, the instability of measuring system, and the irregular distribution of samplinng points.
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