A method of detecting the presence of a building in a captured image is provided. The method includes dividing the captured image into a plurality of image regions, detecting a dominant angle of detected edges within each image region, and detecting the presence of a building in an image region if the dominant angle of detected edges within that image region, excluding edges within a first threshold angle of vertical, is within a second threshold angle of horizontal and if the distribution of detected edges within the second threshold angle of horizontal is substantially the same as that of at least one adjacent image region.