A measurement system for 3-D foot shapes under different loads and the practical global calibration principle of CCD cameras based on coordinate mapping and POWEL optimization method were described. The model of the measurement system was constructed based on four coordinate systems

the visual point-net grid in light plane and in CCD camera image planes was formed through the scanning of two inclined planes and the mapping relations were constructed. Finally

the objective function based on transform coefficients between different coordinate systems was defined and the transform parameters were optimized by POWEL method. Measurement results show that the repetitive error of single CCD camera is 0.062 5% and the relative measuring error of four CCDs is 0.365%. Experimental results prove that the simple and practical global calibration method can be used in the spot calibration of the measurement system

and installation errors and nonlinearity of CCD cameras can be reduced.