Method and system for navigation of an unmanned aerial vehicle in an urban environment

A method and system for navigation of an unmanned aerial vehicle (UAV) (110) in an urban environment (120) are provided. The method comprises capturing a first set of Global Positioning System (GPS)-tagged images in an initial fly-over of the urban environment at a first altitude (A), with each of the GPS-tagged images being related to respective GPS-aided positions. The captured GPS-tagged images are stitched together into an image mosaic using the GPS-aided positions. A second set of images is captured in a subsequent fly-over of the urban environment at a second altitude that is lower than the first altitude. Image features from the second set of images are matched with image features from the image mosaic during the subsequent fly-over. A current position of the UAV relative to the GPS-aided positions is calculated based on the matched image features from the second set of images and the image mosaic.