Page 109 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

88 Maritime Archaeology: A Technical Handbook, Second Edition
data are recorded on land prior to processing. It is worth printing up record- ing sheets, once the survey system is established, to help the underwater recording. It is also worth considering voice communications, so that these data can be transferred directly to the surface and, in the ideal situation, processed on the spot. This ensures the readings are correct and helps to make a good fix. With programs such as Site Surveyor (see Section VI.D), it would not be difficult to set the system up so that the measurements were transferred directly to the surface computer operator. The operator then enters these data directly into the program and confirms the fix. This could greatly increase the efficiency of the system. In situations where it is diffi- cult and time-consuming to return to the site and re-measure an object, or where an artifact cannot be removed until its coordinates have been con- firmed, it will be necessary to make at least five or more independent mea- surements. This ensures that if one measurement is wrong there is enough redundancy to still obtain a result. By having voice communication only four measurements will normally be necessary, and if one measurement is wrong the program will identify the measurement so it can easily be re-checked.
A. BASIC SURVEY
The objective of a basic, or first-order, survey is to record the site as it exists. This includes all the topographical information and any other useful data that can be collected quickly, efficiently, and at a relatively low level of accuracy. With this information subsequent, more detailed survey work can be planned. Therefore, the first priority of the basic survey is to deter- mine the approximate extent of the perimeter of the site and to fill in other approximate details. With this information a strategy can be developed to record the more complex and detailed information that will become the main predisturbance plan. Information about dimensions, depths, and physical features together with the potential problems and difficulties of working on the site provide essential information for planning the subse- quent survey work.
Although sites vary in extent and complexity, the principle of working systematically rarely fails. There are obviously a lot of different ways that this first-order survey information can be obtained. For example, one method would be to select a point somewhere on the site (even if this is not the center) and, working in a systematic manner, measure from that point to the extremity of the site in the four orthogonal directions. The