Abstract:Error evaluation is one of the important tests in the process of part inspection. Geometric fi tting is the core content in the error evaluation based on the coordinate measuring. Based on the analysis of the common geometric elements, the parameterized mathematic model of geometric elements is constructed and the frame of the fi tting algorithms is proposed. Meanwhile the detail of fitting algorithms and the initial value of the optimization algorithms are illustrated. Then algorithms are carried out on the MATLAB platform and the fitting results are compared with the results of NIST. The comparision shows that the fi tting algorithms are feasible.