Panorama Software - Panoweaver Adjust horizontal and vertical level by YPR
Sometimes a problem will occur after you stitch a panorama, the horizon is curved like this:
This happens if the camera is not leveled well, pointing upwards or downwards when source images are shot. Since panorama is a projection of a sphere (the world around the camera) onto a flat surface, tilting some source images results in the curve in final stitched panorama The 'YPR' function in Panoweavre 9.2 can straighten the curved panorama. To achieve this:
Step 1. Click button
to enter YPR Mode, in this mode the panorama is divided into many dragable parts;

Step 2.Use the left mouse button to drag the curved part to make the horizon of the panorama match the horizontal line in the Panoweaver editing window;

Step 3: Click button
again to save your change.

Now the horizon is straightened. You can see the comparison below:

Video tutorial of processing in Panoweaver: http://www.easypano.com/video-tutorial/panoweaver-ypr-function.html.
Note: By far only spherical panorama is supported to edit.