Photogrammetry for dish concentrator construction

Photogrammetry has been used to control the assembly of a convex paraboloidal jig, used in the construction of a 500 m² dish concentrator. The photogrammetric measurement precision was ~ 1:175,000, corresponding to an accuracy of better than 1 mm at the jig reference points. Equipment (camera, flash and retro-reflective film) and software are discussed. Photogrammetry was also used to characterise 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 measurement precision attained was ~ 1:150,000