Page 259 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

238 Maritime Archaeology: A Technical Handbook, Second Edition
when carrying out this form of exploratory work; however, provided the work is done carefully, it will provide essential information in planning the excavation strategy. Until the extent of the site is fully understood, it will be impossible to plan how long the work will take or the necessary storage and conservation facilities that will be required. There will be a great deal of difference between the excavation of a site which has an average archae- ological depth of 0.5 m and that of a site which has an archaeological layer 4m thick.
The use of grid frames to assist with excavation needs to be carefully considered. There are a number of advantages and disadvantages attached to using grid frames. On extensive sites with a large staff, grid frames are often used to help define excavation areas and to orientate staff who may be unfamiliar with the site (Figure 9.1). Novice archaeological divers inevitably require some form of coordination and, at times, the grid frame may be the best solution. Otherwise, when left to their own devices, it is not uncommon to find inexperienced staff excavating totally unsystematically in some far off area.
With the grid frame system, one is confined. Grid frames can also be useful supports for the excavators while they are working over a site that has a large quantity of extremely fragile material exposed and, as previ- ously mentioned, are particularly helpful when working with novice divers. Proper buoyancy control and coordination of the excavation using more
Figure 9.1 Excavating using a grid frame, Ko Kradat wreck site, Thailand.