Viability of Using Shadows Cast by Vehicles for Position Verification in Vehicle Platooning

This work investigates the viability of using the visible shadows cast by vehicles to verify position claims made by vehicles in a platoon. Platooning is a method of guiding a group of vehicles whereby a lead vehicle determines the speed/velocity of the vehicles that follow. A cooperative following strategy is then employed by the followers to maintain a desired separation between themselves. In this way a group of vehicles acts as a single unit, which has been shown to have many safety and efficiency benefits. Existing work, however, demonstrates that a disruptive member of a platoon is capable of causing the rest of the platoon to increase its total energy expenditure, or even destabilizing the platoon, which could result in catastrophic accidents. Knowledge about the position and velocity of each vehicle can help deter such attacks by attributing the disruption to the specific vehicle causing it.One way to achieve this is to assume that the lead vehicle is trusted and equipped with a camera so as to watch over the platoon and identify deviations from reported positions/velocities. As platoons often move in a straight line, it might be impossible for the leader to obtain a direct view of all the vehicles in the platoon. Under a broad range of circumstances, however, a direct view of the vehicle or the shadows of the vehicles are visible to the leader. In this work we investigate whether the differential distance between shadows, as viewed through a monocular camera, can reveal that the distance between two vehicles has changed over time, and thus serve as a mechanism to verify positions claims. When a direct view of the vehicle is not achievable, the use of shadows to detect the relative positions of vehicles under a variety of weather and daylight conditions are considered. Our analysis finds that shadow analysis can be used in sequential images to detect practical changes in the distance between two vehicles for visible shadows in non-light-of-sightscenarios. We also present the analysis to efficiently use the technique as the position of the Sun changes through out the day for a given site location.