1. An in vivo imaging system comprising: an in-vivo device including at least an orientation indication apparatus and an imager configured to produce an image, wherein the orientation indication apparatus is positioned in the field of view the imager; and a processor, wherein said processor is configured to measure a size of said orientation indication apparatus and to calculate an angle of said orientation indication apparatus relative to the imager and to determine the orientation of the imager relative to gravitational force therefrom.