A method of generating a comprehensive image (87) of interior surfaces (78, 80) of machine components such as a gas turbine combustor basket (59) and transition duct (34) by digitally stitching together multiple photographs (82) thereof, and analyzing the comprehensive image by contouring (91, 95A-B) of colors and shadings thereon, and quantifying and tracking aspects of the contours (A, B, C) over time for indications of degradation (89) of the interior surfaces. A scope (58) may be inserted into a port (56) in the combustor with a camera (72, 74) in a rotatable end (70) of the scope for obtaining a circumferential set (84) of photos at each axial position along a length of the combustor and transition duct. A 3D surface scanning device (76) in the scope may define the geometry of the interior surface for 3D photographic modeling thereof providing a virtual walk-through inspection.