A trailer assist system for a vehicle includes a camera with a field of view encompassing a trailer hitch disposed at the vehicle. A control includes an image processor that processes image data captured by the camera that is representative of images of the trailer hitch present in the field of view of the camera. The control, responsive to processing at the control of image data captured by the camera, detects at least one feature of the trailer hitch at a Cartesian coordinate location and transforms the Cartesian coordinate location of the detected feature to a cylindrical coordinate location. The control generates a vertical segment that passes through the detected features and determines cylindrical coordinates of a ground point along the vertical segment. The control, responsive to determining the cylindrical coordinates of the ground point, determines a 3D location of the trailer hitch at the vehicle.