Stitching can be as simple as a 2 image match for a Bubble Panorama or one of a number of edge matched methods reprojected as cylinder, sphere, perspective, rectilinear.
multi image of projection types

How many images?
Fewer is better.
Using a very wide lens with a deep overlap causes stitching difficulties.

How much overlap?
It is suggested that you shoot each photo with 15 to 20% overlap. It is preferable to use a lens which doesn’t have distortion toward the edges. If you use a wide-angle lens, the edge of the image will be severely distorted, and you will have difficulty stitching the photos due to the distortion in the overlapping
sections.
Sim Hyun-Jun

Taking the shots as quickly as possible helps reduce variation in exposure and limit the amount of camera travel.

Camera aspect
A portrait mounted camera is likely to get better stitching across the horizon line

360° Bubble Panoramas
Only two images are needed to create these panoramas. I take one looking straight down from the kite using a simple rig, and a second looking straight up from the ground. Both images are shot with a circular fisheye lens that has a 180 degree view (Nikon FC-E9).
You can think of it as if each image contains a “hemisphere” of information: the image from the kite is the southern hemisphere, and the image from the ground is the northern hemisphere. When you rotate around in the image, you are viewing it from the center of a sphere that you’re inside of. The image is
projected onto the walls of the sphere; It’s like being at the center of a bubble, looking around.
First, I touch up the two initial images, fixing color balance, contrast, etc.

I stretch the sky shot vertically so that any visible ground features can be hidden behind the ground shot in the composite image. Then I use a layer mask to make the seam between the two images as discreet as possible.
Scott Haefner

Software tools for panorama building