A metrology system containing an interferometer for remote analysis of a gaseous compound by Fourier transform spectroscopy, said interferometer being a two-arm interferometer containing at least one movable retroreflector and having a field of view in which the gaseous compound is viewed, the metrology system further containing at least: • a sub-system for injecting at least three metrology laser beams into the interferometer, the at least three laser beams being distributed in the field of view of the interferometer and the three injection positions being spaced apart from each other; • a sub-system (48, 49) for acquiring the at least three metrology laser beams output from the interferometer, said acquisition sub-system (48, 49) supplying at least three laser signals each representing an interference measurement of a metrology laser beam after its passage through the interferometer; • at least one metrology unit containing at least three metrology computation units (70, 74, 75) estimating, for each acquired laser beam, an absolute optical path difference associated with the corresponding laser signal and with the corresponding measurement point, and computing, for each acquired laser beam, a raw metrology signal on the basis of the laser signal, and a unit for generating a synthetic metrology reading per measurement point, which unit, on the basis of the raw metrology signals, digitally generates a synthetic metrology signal for each measurement point associated with the field of view of the interferometer, the synthetic metrology signals thus generated taking into account the trajectory of the movable retroreflector in space; • the movable retroreflector having the form of a corner-cube and the unit for generating a synthetic metrology reading per measurement point performing at least the following processes: ∘ estimating an apex vector connecting the positions of the vertices of the movable retroreflector; ∘ removing the linear component of the apex vector; ∘ generating at least one optical path difference represented by a synthetic metrology signal, at a point of the field of view, from the apex vector and angular coordinates of said point of the field of view. • a sub-system for injecting at least three metrology laser beams into the interferometer, the at least three laser beams being distributed in the field of view of the interferometer and the three injection positions being spaced apart from each other; • a sub-system (48, 49) for acquiring the at least three metrology laser beams output from the interferometer, said acquisition sub-system (48, 49) supplying at least three laser signals each representing an interference measurement of a metrology laser beam after its passage through the interferometer; • at least one metrology unit containing at least three metrology computation units (70, 74, 75) estimating, for each acquired laser beam, an absolute optical path difference associated with the corresponding laser signal and with the corresponding measurement point, and computing, for each acquired laser beam, a raw metrology signal on the basis of the laser signal, and a unit for generating a synthetic metrology reading per measurement point, which unit, on the basis of the raw metrology signals, digitally generates a synthetic metrology signal for each measurement point associated with the field of view of the interferometer, the synthetic metrology signals thus generated taking into account the trajectory of the movable retroreflector in space; • the movable retroreflector having the form of a corner-cube and the unit for generating a synthetic metrology reading per measurement point performing at least the following processes: ∘ estimating an apex vector connecting the positions of the vertices of the movable retroreflector; ∘ removing the linear component of the apex vector; ∘ generating at least one optical path difference represented by a synthetic metrology signal, at a point of the field of view, from the apex vector and angular coordinates of said point of the field of view. ∘ estimating an apex vector connecting the positions of the vertices of the movable retroreflector; ∘ removing the linear component of the apex vector; ∘ generating at least one optical path difference represented by a synthetic metrology signal, at a point of the field of view, from the apex vector and angular coordinates of said point of the field of view.