The disclosure relates to a method and system of electron beam scanning for measurement, inspection or review. The plurality of vacuum fan housing comprise a first vacuum fan housing and a second vacuum fan housing. The tool also includes a photodetector array positioned at a detector surface to detect the light scattering pattern as it reaches the detector surface. By analysis of the data displacements from the origin or datum in succession, the pipeline may be located and mapped in an as-built position from a frame of reference, i. A smoothing algorithm is used to increasedecrease the BRD andor CRD acquisition times to account for signal variations in BRDCRD measurement readings.