National Ignition Facility (NIF) ignition target specifications require submicron dimensional measurement accuracy for the spherical ablator shell, which requires the proper corrections of various distortions induced by the imaging lens, the point projection geometry, and x-ray refraction. The procedures we developed allow measurement accuracies of 0.5 m for the capsule diameter, ±0.2 m for the out-of-round (which is the amplitude of the radius variations), ±0.3 m for the wall thickness (including each sub-layer), and ±0.1 m for wall thickness profile.