LASER-BASED LEVELLING SYSTEM

The invention relates to a method for deriving alignment information of a surface of a structure, the alignment information comprising a deviation of an alignment of the surface with respect to a light plane. The method comprises detecting at a plurality of light-receiver units, an impingement position of the light plane on a photo sensor that has a known relative position in relation to the surface, determining, for each light-receiver unit and based on the impingement position and the known relative position, a crossing position value of the light plane with respect to the surface, performing a combined analysis of the crossing position values from the plurality of light-receiver units to derive alignment information comprising the deviation of the alignment of the surface of the structure relative to the light plane, and displaying the alignment information to a user. The invention also relates to computer programme product, a light-receiver unit and a system comprising a plurality of light-receiver units for performing the method.