A method and system for determining surface topology of a three-dimensional (3D) structure, based on a structured pattern that is projected onto the surface structure, and images of the pattern superposed on the structured surface are analysed to provide surface coordinates of the structure. The pattern comprises a plurality of unique color edges defined between pairs of differently-colored stripes, which substantially overcomes ambiguity problems. In one embodiment, a calibration method is provided enabling the surface coordinates to be obtained from a single image of the structure.