A measurement system measures a gap between a plurality of rotating bucket tips and a stationary shroud surface. The system includes a sensor secured to the shroud surface, where the sensor senses a distance between each of the rotating bucket tips and the shroud surface, and a key phasor indexing each of the plurality of rotating bucket tips. A processor receives data from the sensor and the key phasor and calculates a shift against each of the plurality of buckets. The processor determines a time to bucket replacement based on current service hours of the plurality of rotating buckets tips.