Cylindrical implosion offers a path to extreme material states, reaching considerably higher pressures than planar geometry. However, diagnosing compressed material in cylindrical geometry is challenging. Time-resolved velocimetry, a standard technique in planar compression, is difficult to incorporate into cylindrical experiments. This paper describes the use of photonic Doppler velocimetry (PDV) in magnetically driven cylindrical compression experiments at the Sandia Z machine. With this diagnostic, it is possible to track the interior of an imploding cylinder beyond 20 km/s. A "leapfrog" implementation is described to support velocities well above the bandwidth limits of standard PDV measurements.