What is the principal point in an aerial photo?

The principal point in an aerial photo refers to the center point of the photograph. This is crucial for understanding aerial imagery because it acts as a reference from which measurements and analyses are often made. The principal point marks the intersection of the optical axis of the camera with the ground and is typically found geometrically at the center of the image. Understanding this point is essential for tasks such as orthorectification, where the aerial photo is adjusted to accurately represent spatial relationships and scales on the Earth's surface.

Other aspects that pertain to aerial photography, such as the highest point in an image or the focal point of the camera, do not accurately define the principal point, as they relate more to features within the image or the camera configuration rather than the photograph's center. The origin of the photograph may also refer to its geographical starting point rather than its geometric center, which is specifically what the principal point describes.