The Zenit is the upward picture and the Nadir the downward picture taken to complete a full 360x180° panoramic image. But in this set, the Zenit is missing unfortunately. No picture of the sky. Only this silly Truck blocking the street view:
This results in a project with empty Zenit, and in this case for this tutorial, a Nadir with a hole due to masked shadows:
To fix this, check for a matching picture in your collection. In this case, one with sunny sky taken at about the same time. It doesn't need to be a Zenit shot. If not available, it is also possible to create an image with similar content using an image editor:
To fix the Nadir, add a copy of the current Nadir picture to the project and manually position the copy over the hole. Often the texture of the bottom is like that and using a copy works nicely:
The new Zenit from the added picture is positioned manually to cover the missing sky. You cannot use control points here unless this is a shot from the same location with matching features.
Both the new Zenit and the copy of the Nadir gets a mask to avoid wrong seam lines when the panorama gets completed:
The added areas are positioned:
The PTGui blender makes sure that there is gradual transition between the stitched pictures to make it look perfect:
The final stitched panorama.
