In this study, an application of two dimensional ultrasonic doppler flow mapping was undertaken on a strong full air core free-surface vortex. The vortex was generated in a scroll type vortex chamber with a subcritical approach flow which have common application in hydraulic structures such as sewer vortex dropshafts and energy dissipaters. A 2D array of ultrasonic Doppler profilers was arranged on the vortex chamber using 7 vertical and 7 horizontally arranged transducers to generate 2D flow maps of the secondary flow field to capture the radial and axial velocity fields. The transducers were multiplexed in a diagonal fashion to generate quasi-instantaneous flow maps of the secondary flow. The 2D velocity fields were smoothed using kriging interpolation and post processed using ParaView. The results highlight interesting cellular structures which develop in the secondary flow along with other global features. These observations have strong implications to improve an understanding of free-surface vortex mechanics and stability.