Collinearity equation
![Light beams passing through the pinhole of a pinhole camera](/Images/godic/202501/05/NYW-CentralProjektion014434.png")
![The three points P, Q and R are projected on the plane S through the projection centre C](/Images/godic/202501/05/NYW-CentralProjection024434.png")
![x- and z-axis of the projection of P through the projection centre C](/Images/godic/202501/05/NYW-CentralProjection034434.png")
The collinearity equations are a set of two equations, used in photogrammetry and remote sensing to relate coordinates in a sensor plane (in two dimensions) to object coordinates (in three dimensions). The equations originate from the central projection of a point of the object through the optical centre of the camera to the image on the sensor plane.