Drivers often park their vehicles without consciously (physically or mentally) noting down theparked location which makes it hard and inconvenient for the users to later locate their vehicles. Existingsolutions either require users to explicitly note down the parked position on their mobile device by performinga certain action, such as pressing a button to turn on their global positioning system, or are erroneous andinaccurate. This paper attempts to build ParkSense, a system that allows a smart phone to accurately andautomatically ‘‘sense,’’ and later navigate to, the position at which the vehicle was parked. We propose tomake use of the variations of magnetic fields and electromagnetic fields inside the vehicles to detect whena user stops and turns off his or her vehicle. Our evaluation with an actual implementation of the system ondifferent mobile platforms and operating systems, tested on different mobile devices/phones and car models,shows the detection accuracy of more than 90%, confirming the feasibility of our approach.