1. A method comprising: providing a first three-dimensional (3D) point cloud obtained according to a first sensing technique, a second three-dimensional point cloud obtained according to a second sensing technique and a first radius of a sphere covering a real object underlying the first three-dimensional point cloud and a second radius of a sphere covering a real object underlying the second three-dimensional point cloud; defining a scale of the first three-dimensional point cloud based on said first radius and a scale of the second three-dimensional point cloud based on said second radius; searching at least some candidate regions between the first three-dimensional point cloud and the second three-dimensional point cloud using an ensemble shape function (ESF); aligning the searched candidate regions between the first three-dimensional point cloud and the second three-dimensional point cloud at least in a vertical direction; and ranking the aligned candidate regions between the three-dimensional point clouds based on their structural similarity.