Turbine blade tip clearance is measured in a fully assembled turbine casing by mounting a contact or non-contact displacement probe on a turbine blade that generates data indicative of probe distance from the turbine casing that circumferentially surrounds the blade. Variations in probe distance data are recorded as the blade circumferentially sweeps the turbine casing when the turbine is operated in turning gear mode. Blade rotational position data are collected by a rotational position sensor. A data processing system correlates the distance and rotational position data with localized blade tip gap at angular positions about the turbine casing circumference. An optical camera inspection system may be coupled to a turbine blade to obtain visual inspection information within the turbine casing. This method and apparatus provide an accurate and cost effective solution for accessing turbine casing deformation impact on blade tip clearance and rotor/casing alignment.