We report rovibrational calculations from an empirical potential energy surface (PES) of the electronic ground state of ozone, using an Exact Kinetic Energy (EKE) operator. The PES was optimised using the EKE Hamiltonian and experimental spectroscopic high-resolution data. The RMS deviation of calculations for all experimental band centres directly observed so far in high-resolution spectra is 0.12 cm(-1). The RMS deviation of calculations of rotational energies up to J less than or equal to 5 is 0.002 cm(-1) for the (000) level and 0.015 cm(-1) for five lowest vibrational states. Both rotational and vibrational calculations are cm more accurate than presently available EKE-calculations for O-3. The PES shows a physically meaningful long-range behaviour at the dissociation limit.