Each Panorama is a complete circle of visual information. Everything you can see standing in one place and looking up and down and all around in front and behind your position. Due to this fact whatever is behind you being brought around and to be viewed in front of you requires some substantial amount of distortion. This is the same type of projection map makers use to illustrate the world map with lots of exaggerated perspective at the poles..
Changing the position of the poles (north and south poles, or the Zeinith and Nadir point) means the perspective is even more unusual and lines are seldom straight.
© John Anderson, Photographer