A fork-lift truck 1, 1′ including a load carrier 2, an optical detector 3, 3′ having a first field of view and arranged to provide an output, wherein the optical detector 3, 3′ is movable together with the load carrier 2, an optical analysing unit 4, 4′ arranged to analyse the output from said optical detector 3, 3′. The optical analysing unit 4, 4′ is arranged to analyse the output from the optical detector 3, 3′ so as to identify a first three-dimensional object, said first three-dimensional object being the load carrier 2, and a second three-dimensional object based on the output from the optical detector 3, 3′, and to determine the three-dimensional position of the identified load carrier 2 relative to the identified second three-dimensional object. Further a method for operating a fork-lift truck, a method for modifying a fork-lift truck and a computer program product.