1. A method comprising: receiving an image captured by an image capturing device in communication with a probe apparatus on board a vehicle, wherein the image comprises at least a portion of a roadway; generating a sky projection based on at least a portion of the image; determining whether the sky projection comprises a feature that defines a feature direction that is substantially non-vertical; and responsive to determining that the sky projection does comprise a feature that defines a feature direction that is substantially non-vertical, determining that the image comprises an overhanging structure.