  In this work, inspired by the definition of the photon surface given by
Claudel, Virbhadra, and Ellis, we give an alternative quasi-local definition to
study the circular orbits of single-pole particles. This definition does not
only apply to photons but also to massive point particles. For the case of
photons in spherically symmetric spacetime, it will give a photon surface
equivalent to the result of Claudel, Virbhadra, and Ellis. Meanwhile, in
general static and stationary spacetime, this definition can be regarded as a
quasi-local form of the effective potential method. However, unlike the
effective potential method which can not define the effective potential in
dynamical spacetime, this definition can be applied to dynamical spacetime.
Further, we generalize this definition directly to the case of pole-dipole
particles. In static spherical symmetry spacetime, we verify the correctness of
this generalization by comparing the results obtained by the effective
potential method.
