What role does the directional element play in the coordinate system transformation of general photogrammetry?

Directional elements play a role in determining the position in the coordinate system transformation of general photogrammetry.

The internal orientation element is a parameter that determines the relationship between the camera lens center (strictly speaking, it should be the image node of the lens) and the image position. It includes three parameters: the positions x and y of the main point of the image (the vertical foot of the main optical axis on the image plane) relative to the image center, and the vertical distance f (the main distance) from the lens center to the image plane, which is generally determined by camera calibration.

Determination of internal orientation elements

This is done by camera calibration. Because of the diversity of cameras and calibration methods, camera calibration is not standardized. According to different calibration environments, the commonly used calibration methods include control field-based calibration method (optical laboratory calibration method, experimental field calibration method), in-service calibration method (that is, camera calibration while completing a certain measurement task), self-checking calibration method, star point calibration method and vanishing point-based calibration method.