Why does my iPhone panorama have black lines on top / bottom?

The iPhone makes taking panoramic photos easy, if the photographer takes note of a few simple tips and tricks. Sometimes PANO mode on the iOS Camera app doesn't deliver the expected results. One of the problems iPhone photographers sometimes encounter are black lines on the top or bottom of a panorama. Why do the black lines appear in some panoramas?

iOS Panorama

The black spaces on iPhone panoramas are areas where the camera was unable to capture data matching the surrounding scene. Usually this happens because the iOS camera was tilted too far up or down while panning.

To avoid black lines in panoramic photos, keep the white arrow as close to the center line as possible while recording. Also, pan more slowly when prompted by the camera viewfinder. Moving too fast can lead to gaps in data and black lines on the panorama.