Spherical panoramas can be tricky to stitch properly in dense forests, and especially when canopy elements are very close to the camera (which exaggerates the parallax). Fortunately, the issue attenuated with every update of phone software, but it still pays to be careful when capturing your panoramas. So, if you are taking spherical panos in order to estimate canopy metrics, here are my suggestions for improving your captures:
Rotate around the camera
Perfecting panoramas took some practice for me. The first key is to avoid rotating the camera around your body, but rather, to rotate your body around the camera. I found this post helpful when I was learning. The principle is to keep the entrance pupil of the camera lens as the exact center of the sphere (as much as possible).
Calibrate your compass and gyro
Another tip is to calibrate your compass and gyro regularly (here’s how for Android users). If the compass is off, the phone won’t always know when you’ve made a full rotation.
Take your time
It also helps to go slowly. The camera is constantly processing and mapping the scene to guide the next image, which takes a few seconds.
Be consistent
Even though you can technically take images in any order, I always rotate the same direction around the horizon and then the upper two circles. The lower sphere doesn’t really matter, so I don’t spend much time on it. The key here is that consistency, both for you and the camera, helps.
Use your body as a tripod
You can also try to use your body as a kind of tripod. I used a specific method when I was first learning to take spherical images: I hold my right elbow to my hip bone directly over my right knee and pinch the phone at the top in line with the camera. Then I keep my right foot planted and walk my left foot around the right, using my left hand to tip the phone as need. After a few dozen spheres, I don’t really need to do that any more. I usually know if the sphere will turn out bad and just restart.
Review your images
It is important to remember that you can (and should) review your images in the field so that you can retake any with issues. You can also get a Google Cardboard viewer for $13 which lets you review the sphere in VR in the field to more clearly see the images.
Over time, you get the hang of capturing spheres to minimize problems. It takes me much less time to get a good photosphere than it does to level and set my exposure with my DSLR, now that I have practiced.
Nevertheless, there are always some artifacts. After looking at lots of images side-by-side, my sense is that the artifactual errors in the panos, even when fairly large, contribute less error than the total errors of incorrect orientation, unleveled camera, poor lens calibrate, exposure misspecification, and much lower pixel count from other methods.
Be sure to check out my other posts on this topic:
Smartphone hemispherical photography
Analyzing hemispherical photos
Taking hemispherical canopy photos