Page 52 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

Chapter 3: Search and Survey 31
d
Figure 3.4 (Continued) and (d) shows site in 2003. Note that in all pictures some features are common, particularly the silos seen in (a). It should be noted that as the vegetation develops more and more features become obscure, and by 2003 most of the site is totally unrecognizable. (Figures 3.4b and c are courtesy of Patrick Baker, Department of Maritime Archaeology, Western Australian Maritime Museum.)
to utilize oblique photographs to locate position by rectification. One example is an aerial reconnaissance photograph of aircraft burning in Broome, Western Australia, after a Japanese raid during WW II (Figure 3.5). This was rectified to identify the locations of the aircraft (Green, 2002, p. 129). In this case there were features in the photograph that could be identified on a modern map. These features were used to calculate the orientation of the photograph and thus allowed the locations to be determined.
When surveying close to shore, it is sometimes possible to utilize natural transits to operate a systematic search pattern. However, as this requires the fortuitous location of regularly spaced features such as street lights or bridge railings, this situation is unusual. A far more common approach is to set up a transit network on the beach using a series of poles separated by the required lane width (Figure 3.6). A land survey party first places the back markers in a line at approximately right angles to the lanes required. The pole separation is measured with a tape and can be aligned by visual sighting. These back markers must be located as far up the beach as possi- ble to give the greatest separation from the front markers. Using a simple optical square, or some other method of determining a right angle (theodo- lite, 3–4–5 triangle, etc.), the first pole of the front markers can be put in position. Using the optical square again, some place up the run the position