This paper proposed a novel method of image unwrapping for spherical omnidirectional images acquired through a nonsingle viewpoint omnidirectional sensor. The proposed method comprises of three key steps, i.e. 1) calibrate the camera to obtain parameters describing the spherical omnidirectional sensor, 2) map world points onto mirror points and, subsequently, onto image points, and 3) set up the projection plane for the final image unwrapping. Depending on the projection plane selected, the algorithm is able to produce either the cylindrical panoramic, the cubloid panoramic, or the ground plane view using closed form mapping equations derived herein. The motivation for developing this technique is to address the complexity in using non-single viewpoint omnidirectional sensor; and ultimately promotes its adoption in robotics.