Page 214 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

Chapter 6: Photogrammetric Techniques 193
were recorded, they could be quickly processed and the object then safely removed, at best about one hour after that data reached the surface. Thus often hand measurements were used in preference to photogrammetry.
In the third season, an underwater digital camera was used. This was a 3.3 mega pixel Olympus Camedia 3000 digital camera mounted in a custom- made Wills camera housing with a wide-angle lens and corrected dome port (Figure 6.16). The camera system was calibrated prior to the expedition and used for all recording work (4.71mm focal length on a 6.26 ¥ 4.69mm format, equating to a 27-mm lens in the 35-mm film format). This system proved to be an ideal solution. At the end of each dive the case was opened, the Smart Media card extracted from the camera, and these data were downloaded directly into the computer (taking about a minute). The images were thus immediately available for processing by PhotoModeler and results were generally available within less than 30 minutes after the camera arrived at the surface (depending on the complexity of the model). The quality of the image was as good, if not better, than the Nikonos system; the only drawback was the rather long focal length. The rechargeable bat- teries lasted 4 hours, more than enough for the two dives each day, and the
Figure 6.16 UW digital camera. This system is an Olympus Camedia 3000 camera mounted in a custom-built Wills camera housing.