This picture was cropped to a square from the original rectangular frame taken by the CP 990.

From a previous lens calibration, the Horizontal Field Of View (HOFV) of this circular photo is 189.6deg. This information is needed for the next step.

With the help of the photoshop plug-in "Adjust" tool from PTools transform this circular image into an equirectangular format picture.

See how this picture can show you the ROLL ERROR or the camera.