Photogrammetric monitoring of the construction of a solar energy dish concentrator

Close-range photogrammetry has been used to control the construction of a jig used in the assembly of a new generation solar concentrator and the validation of the final, mirrored surface. The concentrator is a concave paraboloid dish with an area of a 489 m2. The typical photogrammetric relative precision realized was 1:175,000, corresponding to an accuracy of better than 1 mm at the jig reference points. The validation of the mirrored surface achieved a relative precision of 1:300,000. Photogrammetry was also used to characterize the dish mirror panels. The rear surface of the panels was mapped, as it made possible a denser target array and quicker image capture than if the reflective surface was used. The targets were produced with a digital projector, and the typical measurement precision attained was 1:150,000. This paper describes the equipment and techniques required to provide the required accuracy and precision for the jig and panel surfaces.