Method for calibrating alignment biases of an earth observation system using symmetrical photographs

The method involves comparing a reference image (R) of a scene with a secondary image (S) of the scene acquired by an imaging system, where the images consist of exposures of the scene acquired by the imaging system. Movement direction of an observation satellite during the exposure of the secondary image is determined to be opposite to movement direction of the observation satellite during the exposure of the reference image. A line and a column of a matrix obtained by correlation of the reference and secondary images are averaged to estimate a pitch error and a roll error. Independent claims are also included for the following: (1) a computer program product comprising a set of instructions for calibrating alignment errors of a reference mark of an on-board imaging system inside an observation satellite (2) a imaging system for on-board an observation satellite.