A method for determining spindle angles of a steerable wheel axle arrangement, said steerable wheel axle arrangement comprising a wheel axle and a spindle (122, 124) pivotably connected to the wheel axle at a first, outer end position of the wheel axle, wherein at least one wheel axle optical marker (130, 130') is arranged in connection with the wheel axle and a spindle optical marker (132, 134) is arranged in connection with the spindle (122, 124), wherein the method comprises the steps of: - acquiring, by an image capturing arrangement, an image of the at least one wheel axle optical marker (130, 130') and an image of the spindle optical marker (122, 124) for determining a position of each one of the at least one wheel axle optical marker (130, 130') and the spindle optical marker (132, 134) relative to the image capturing arrangement; - determining a wheel axle coordinate system of the at least one wheel axle optical marker (130, 130') relative to the image capturing arrangement; - determining a spindle coordinate system (142, 144) of the spindle optical marker (132, 134) relative to the image capturing arrangement; - determining a position of the spindle coordinate system (142, 144) relative to the wheel axle coordinate system; - rotating said spindle (122, 124) relative to said wheel axle; - acquiring at least two different positions of the origin (143, 145) of the spindle coordinate system (142, 144) relative to the wheel axle coordinate system when rotating the spindle; and - determining a center of rotation (147, 149) and an axis of rotation (151, 153) of the spindle (122, 124) relative to the wheel axle coordinate system based on the at least two different positions. - acquiring, by an image capturing arrangement, an image of the at least one wheel axle optical marker (130, 130') and an image of the spindle optical marker (122, 124) for determining a position of each one of the at least one wheel axle optical marker (130, 130') and the spindle optical marker (132, 134) relative to the image capturing arrangement; - determining a wheel axle coordinate system of the at least one wheel axle optical marker (130, 130') relative to the image capturing arrangement; - determining a spindle coordinate system (142, 144) of the spindle optical marker (132, 134) relative to the image capturing arrangement; - determining a position of the spindle coordinate system (142, 144) relative to the wheel axle coordinate system; - rotating said spindle (122, 124) relative to said wheel axle; - acquiring at least two different positions of the origin (143, 145) of the spindle coordinate system (142, 144) relative to the wheel axle coordinate system when rotating the spindle; and - determining a center of rotation (147, 149) and an axis of rotation (151, 153) of the spindle (122, 124) relative to the wheel axle coordinate system based on the at least two different positions. - acquiring at least two different positions of the origin (143, 145) of the spindle coordinate system (142, 144) relative to the wheel axle coordinate system when rotating the spindle; and - determining a center of rotation (147, 149) and an axis of rotation (151, 153) of the spindle (122, 124) relative to the wheel axle coordinate system based on the at least two different positions.