Coordinates in relativistic Hamiltonian mechanics

Physical (covariant and measurable) coordinates of free particles and covariant coordinates of the center of mass of a system of particles are found for the three basic forms of relativistic dynamics. For a system of two directly interacting particles in the point form of dynamics, covariant coordinates are found and the equations of motion reduced to a manifestly covariant form. These equations are generalized to the case of interaction of the particles with an external electromagnetic field.