A method for scanning a workpiece which is a fuselage section of an aircraft, the area of the workpiece to be scanned being a half-barrel shape having a curved section that extends longitudinally and circumferentially, the curved section having a curved cross-sectional profile that is constant or varies smoothly in a longitudinal direction, the method comprising: (a) moving a curved track, formed on an arch frame (32a, 32b), along first and second linear tracks mounted on rail assemblies (28a, 28b) to a first longitudinal position, the rail assemblies being floor mounted and the curved track in the first longitudinal position being disposed radially outward from the curved section of the workpiece so as to ensure no part of the arch frame (32a, 32b) or rail assemblies (28a, 28b) touches the workpiece; (b) adjusting a position of an NDI sensor unit relative to a carriage to which the NDI sensor unit is adjustably coupled by an extendible arm, the carriage in turn being movable along the curved track, and extending the extendable arm to bring the NDI sensor unit into contact with or into proximity to the surface of the workpiece; (c) moving the carriage along the curved track while the curved track is stationary at the first longitudinal position; (d) during step (c), activating the NDI sensor unit to inspect a first strip-shaped area of the curved section of the workpiece; (e) processing signals output from the NDI sensor unit to derive a first strip of scan data characterizing a structural state of the first strip-shaped area of the curved section of the workpiece; (f) during step (c), acquiring location data representing locations of the NDI sensor unit relative to the workpiece; and (g) mapping the first strip of scan data to a three-dimensional model of the workpiece based on the location data acquired in step (f); (h) subsequent to step (c), retracting the extendible arm to lift the NDI sensor unit, moving the curved track along the first and second linear tracks from the first longitudinal position to a second longitudinal position, the curved track in the second longitudinal position being disposed radially outward from the curved section of the workpiece, and extending the extendible arm to return the NDI sensor unit to contact or be into proximity to the surface of the workpiece; (i) moving the carriage along the curved track while the curved track is stationary at the second longitudinal position; (j) during step (i), activating the NDI sensor unit to inspect a second strip-shaped area of the curved section of the workpiece; (k) processing signals output from the NDI sensor unit to derive a second strip of scan data characterizing a structural state of the second strip-shaped area of the curved section of the workpiece; (l) during step (i), acquiring location data representing locations of the NDI sensor unit relative to the workpiece; and (m) mapping the second strip of scan data to the three-dimensional model of the workpiece based on the location data acquired in step. (a) moving a curved track, formed on an arch frame (32a, 32b), along first and second linear tracks mounted on rail assemblies (28a, 28b) to a first longitudinal position, the rail assemblies being floor mounted and the curved track in the first longitudinal position being disposed radially outward from the curved section of the workpiece so as to ensure no part of the arch frame (32a, 32b) or rail assemblies (28a, 28b) touches the workpiece; (b) adjusting a position of an NDI sensor unit relative to a carriage to which the NDI sensor unit is adjustably coupled by an extendible arm, the carriage in turn being movable along the curved track, and extending the extendable arm to bring the NDI sensor unit into contact with or into proximity to the surface of the workpiece; (c) moving the carriage along the curved track while the curved track is stationary at the first longitudinal position; (d) during step (c), activating the NDI sensor unit to inspect a first strip-shaped area of the curved section of the workpiece; (e) processing signals output from the NDI sensor unit to derive a first strip of scan data characterizing a structural state of the first strip-shaped area of the curved section of the workpiece; (f) during step (c), acquiring location data representing locations of the NDI sensor unit relative to the workpiece; and (g) mapping the first strip of scan data to a three-dimensional model of the workpiece based on the location data acquired in step (f); (h) subsequent to step (c), retracting the extendible arm to lift the NDI sensor unit, moving the curved track along the first and second linear tracks from the first longitudinal position to a second longitudinal position, the curved track in the second longitudinal position being disposed radially outward from the curved section of the workpiece, and extending the extendible arm to return the NDI sensor unit to contact or be into proximity to the surface of the workpiece; (i) moving the carriage along the curved track while the curved track is stationary at the second longitudinal position; (j) during step (i), activating the NDI sensor unit to inspect a second strip-shaped area of the curved section of the workpiece; (k) processing signals output from the NDI sensor unit to derive a second strip of scan data characterizing a structural state of the second strip-shaped area of the curved section of the workpiece; (l) during step (i), acquiring location data representing locations of the NDI sensor unit relative to the workpiece; and (m) mapping the second strip of scan data to the three-dimensional model of the workpiece based on the location data acquired in step.