  We use super-paramagnetic spherical particles which are arranged in a
two-dimensional monolayer at a water/air interface to investigate the crystal
to liquid phase transition. According to the KTHNY theory a crystal melts in
thermal equilibrium by two continuous phase transitions into the isotropic
liquid state with an intermediate phase, commonly known as hexatic phase. We
verify the significance of several criteria based on dynamical and structural
properties to identify the crystal - hexatic and hexatic - isotropic liquid
phase transition for the same experimental data of the given setup. Those
criteria are the bond orientational correlation function, the Larson-Grier
criterion, 2D dynamic Lindemann parameter, the bond-orientational
susceptibility, the 2D Hansen-Verlet rule, the L\"{o}wen-Palberg-Simon
criterion as well as a criterion based on the shape factor of Voronoi cells and
Minkowski functionals. For our system with long range repulsion, the bond order
correlation function and bond order susceptibility works best to identify the
hexatic - isotropic liquid transition and the 2D dynamic Lindemann parameter
identifies unambiguously the hexatic - crystalline transition.
