Vision system and method of analyzing an image

A vision system (1) comprises a camera (5) configured to capture an image (15) and a processor (2) coupled to the camera (5) and configured to determine at least one feature descriptor for the image (15). The processor (2) has an interface (3) to access annotated map data which includes geo-referenced feature descriptors. The processor (2) is configured to perform a matching procedure between the at least one feature descriptor determined for the at least one image (15) and the retrieved geo-referenced feature descriptors.