What refers to the process of removing tilt effects from an aerial photograph?

The process of removing tilt effects from an aerial photograph is known as rectification. Rectification involves mathematically adjusting the image so that it aligns accurately with a particular coordinate system, correcting for any distortions caused by the camera angle at the time the photograph was taken. This is especially important in mapping and surveying because it ensures that the resulting image represents a true, two-dimensional view of the terrain, devoid of any perspective distortions.

In surveying and mapping applications, having a rectified image allows for more accurate measurements and comparisons, as the features represented on the photograph reflect their true positions and dimensions on the ground. This process is vital for generating reliable geographic information systems (GIS) data and for creating accurate maps.

Other terms in the choices represent different concepts. An orthophoto is a specific type of rectified image that has been adjusted to remove geometric distortions, making it geometrically accurate, while a vertical photograph simply refers to an aerial photograph taken from a vertical perspective without any reference to rectification. The principal point refers to the point on the photograph where the optical axis of the camera intersects the image plane, but it does not relate to the process of removing tilt effects.