 <p>You could use background subtraction. This would involve having the empty car park image as your background and then doing a comparison of the changes between that and any subsequent images. If you are looking at car parking spaces then you would want to split the image up into sectors(car park spaces) and do the background subtraction per sector. However due to constant changes in lighting of the carpark as the sun moves you are going to run into issues where the background image will change due to shadows, brightness,etc. An approach to handle this is to do frame by frame comparisons and if it changes by a certain threshold then it is most likely a car has parked rather than the sun has moved as the car will cause a much higher amount of change in a short space of time than the effects of lighting will.</p>