A method is proposed for automatically generating a crane lifting path describing the motion of a crane. The method includes: laser scanning a plant to generate one or more point clouds; using the point clouds to identify objects to be lifted by the crane; rasterizing the laser scanned point clouds to generate digital data describing the plant and in a format for input to a Graphics Processing Unit (GPU); and iteratively optimizing a crane lifting path, including using the GPU and the digital data to detect collisions between one or more cranes and the plant if the crane follows the crane lifting path.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A method of generating a crane lifting path describing the motion of a crane carrying an object within a plant, the method comprising: (i) forming a model of a plant and a model of the crane, wherein the model of the plant comprises a multi-level depth map containing rasterized data; (ii) iteratively optimizing a crane lifting path describing a motion of the crane within the plant, the iterative optimization being performed using the models and at least one graphics processing unit (GPU), to detect collisions between the crane and the plant if the crane follows the crane lifting path. 2. A method according to claim 1 further including, before steps (i) and (ii), the steps of: laser scanning the plant to generate one or more point clouds; using the point clouds to identify an object to be lifted by the crane; and rasterizing the laser scanned point clouds to generate the model of the plant. 3. A method according to claim 1 further including extracting further information about the identified objects from a database. 4. A method according to claim 1 in which the iterative optimization algorithm is a genetic algorithm, in which a plurality of candidate crane lifting paths are evaluated using an objective function, and according to the results new candidate crane lifting paths are generated until a termination criterion is met. 5. A method according to claim 4 in which the objective function of each candidate crane lifting path is a function of at least one of (i) a motion cost indicative of a total distance included in the candidate crane lifting path, and (ii) a time cost indicative of a time taken to implement the candidate crane lifting path. 6. A method according to claim 4 in which the objective function of each candidate crane lifting path further includes a safety cost indicative of the proximity of the crane to the rasterized plant when implementing the candidate crane lifting path. 7. A method according to claim 1 in which, to describe a portion of the crane lifting operation in which the crane is lifting an object, the model of the crane is modified to be a model of the crane and the object. 8. A system comprising a processor and a data storage device storing computer program instructions, the instructions being operative, when performed by the processor, to cause the processor to perform a method according to any preceding claim, to generate and output a crane lifting path. 9. A system according to claim 8 further comprising at least one crane which is configured to implement the crane lifting path. 10. A system according to claim 9 in which the crane is provided with a GPU arranged to detecting real time collisions between the crane and the plant using a multi-level depth map of the crane and the plant. 11. A method according to claim 1 in which the model of the crane comprises an oriented bounding box of the crane.