1. A method of determining functional validity of a vision-based imaging system for a vehicle, the method comprising the steps of: capturing successive images by the vision-based imaging system mounted to a vehicle, the images including landmarks that are identified in multiple images for distinguishing displacement of landmarks between the images; generating an edge map for each of the images by a processing module; comparing like regions of at least two edge maps for distinguishing displacement of a landmark between the at least two edge maps, each edge map being constructed of pixels having varying intensity values, wherein each pixel location of a first edge map is compared with a same pixel location of a second edge map, wherein each of the same pixel locations of the at least two edge maps are compared within one another for determining whether each compared pixel location has a different intensity value; and determining an aggregate number of pixel locations having a different intensity value between the at least two edge maps; determining whether the aggregate number is greater than a threshold for indicating displacement of the landmarks between the at least two edge maps; generating an error message to a driver in response to the aggregate number being less than the threshold; validating a functionality of the vision-based imaging system in response to the aggregate number being greater than a threshold; and generating an error message by an output device in response to determining invalidity of the functionality of the vision-based imaging system.