Camera reverse engineering

Orientation element refers to determining the relationship between objective lens, photo and ground during photographic exposure, including the following contents:

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.

The external orientation element is a parameter that determines the spatial position and posture of the image or the main beam of photography at the moment of photography, including six parameters. Three of them describe the position of the photography center in the object coordinate system X, Y and Z; Three parameters Ω, Φ and κ that describe the attitude.

Direction element:

In order to find the object point from the image point, it is necessary to know the relative position between the projection center, the photo and the ground. The parameters used to determine the relative position between the three are called directional elements. Orientation elements include internal orientation elements and external orientation elements,

Internal direction element:

The parameter that determines the relationship between the photography center and the image position is called the internal orientation element of the image. (principal distance f, frame coordinates (x0, y0) of the principal point of the image), and the inner directional element includes three parameters, namely, the vertical distance (principal distance) f from the photography center S to the photo and the coordinates x0, y0 of the principal point o of the image in the frame coordinate system, which are used for restoring the photographic beam;

External orientation element:

On the basis of recovering the internal orientation elements, the parameters that determine the spatial position and attitude of the light moment in the ground rectangular coordinate system are called external orientation elements. The external orientation elements of a picture include six parameters, three of which are linear elements to describe the spatial coordinate values of the photography center; The other three are angle elements, which are used to express one-sided spatial posture.

Non-photo orientation elements:

The external orientation element of the photo is the basic data to determine the geometric relationship of the photographic beam in the object. It is used to characterize the spatial position of the photographic beam at the moment of photography, including three-dimensional coordinate values (x0, y0, z0) of the photographic center in a certain spatial rectangular coordinate system and three angular orientation elements for determining the spatial orientation of the photographic beam, with a total of six data.