Method of measuring the coupled lattice functions at the interaction point in $e^{+}{e}^{-}$ storage rings

We have investigated a method of measuring the complete lattice functions including the coupling parameters at any azimuthal position in a periodic and symplectic system. In particular, the method is applied to measure the lattice functions at the interaction point where the beams collide. It has been demonstrated that a complete set of lattice functions can be accurately measured with two adjacent beam position monitors and the known transformation matrix between them. As a by-product, the method also automatically measures the complete one-turn matrix.