Sphere
Coordinate projection of a two dimensional sphere into a plane always produces a circular disk. These examples use thirteen circles of latitude on a sphere. On the top left we see the circles of latitude from the side. On the top right we see the circles of latitude from the top. To the side we see the Sammon projection of the circles of latitude. 

To the right we see a hemisphere which has been projected into a plane using the Sammon map. The hemisphere is represented using thirteen semicircles of latitude and two points for the poles. The circles of longitude can be recognized by the color change. This screenshot of HiSee shows the circles of longitude and latitude as they often are in map projections of the Earth. 