Measurement Accuracy Analysis of Multilateral Method Based on Optimal Layout with Non-directional Point Calibration

  Objectives  The measuring accuracy of the multilateral method is affected by the station layout and the calibration errors of system parameters. The optimal station layout and new system parameters calibration method are investigated for optimizing the multilateral method.

  Methods  A spherical center fitting method is introduced to calibrate station coordinates without enhanced reference points. Besides, according to the model error of the multilateral method, the optimal station layout is an equilateral rectangular triangular pyramid.

  Results  In the range of 5 m, the root mean square error (RMSE) of system parameters calibration based on spherical center fitting method is less than 0.006 4 mm, and the RMSE of coordinate measurement of point inside the optimal station layout is less than 0.005 mm. Within the survey region of 5 m, the RMSE of length measurement is less than 0.003 6 mm using optimized multilateral method, and the RMSE of coordinate measurement of optimized multilateral method is less than 0.005 3 mm.

  Conclusions  The optimized multilateral method can achieve high-precision coordinate measurement in a small region. The large-scale 3D coordinate measurement will be studied later using multilateral method.