Archaeology Underwater: The NAS Guide to Principles and Practice
UNDERWATERSURVEY 115 points. The aim of an assessment survey is to get a rough idea of the extent and layout of a site as quickl ...
116 UNDERWATERSURVEY sternpost on an exposed site, or the depth of burial of a site under the sea-bed (see chapter 17). A topogr ...
UNDERWATERSURVEY 117 early stages of a project. Some form of sketch is essential before further work can be planned, as the size ...
118 UNDERWATERSURVEY Expertise – what skills are available? Environment – what can actually be recorded? Funding – what funding ...
UNDERWATERSURVEY 119 around the outside of the site and, if the site is large, pos- sibly through the middle as well. A minimum ...
120 UNDERWATERSURVEY used to securely attach plastic shower-curtain hooks to cannons and anchors. All survey points should be cl ...
UNDERWATERSURVEY 121 a second diver swim up and down the ‘offset’ tape to ensure that it is not snagged. In this case two distan ...
122 UNDERWATERSURVEY Figure 14.6 Ties/trilateration: survey and drawing up results. (Drawing by Graham Scott) ...
UNDERWATERSURVEY 123 SURVEY USING TAPE-MEASURES, GRIDS AND DRAFTING FILM With control points installed on the site, it is now po ...
124 UNDERWATERSURVEY work in pairs where one diver takes measurements while the other ensures that tapes are not snagged. Avoid ...
UNDERWATERSURVEY 125 a clinometer (figure 14.9 and plate 14.3) for mea- suring the tilt of ships’ timbers and structure; large ...
126 UNDERWATERSURVEY To ensure that there is coverage of an area, it is re- commended that some overlap is created between frame ...
UNDERWATERSURVEY 127 PROCESSING MEASUREMENTS AND DRAWING UP THE SITE-PLAN Chapter 19 summarizes information that must be include ...
128 UNDERWATERSURVEY record positions in three dimensions and it is very easy for divers to take the measurements. In addition, ...
UNDERWATERSURVEY 129 of the control points are then considered to be fixed, so the addition of subsequent detailed measurements ...
130 UNDERWATERSURVEY to be extended as more of the site is discovered. The over- all shape of the control point network should r ...
UNDERWATERSURVEY 131 measurement used as a check. It is possible to plot the four points at the same height by hand and to deter ...
132 UNDERWATERSURVEY of the control points. These positions can be plotted on paper charts or imported into a CAD or GIS program ...
UNDERWATERSURVEY 133 reliably position to within 30 mm. The object being posi- tioned has to be connected to the surface by a ca ...
134 UNDERWATERSURVEY to the National Grid or latitude/longitude. The methods of obtaining a position on the surface of the sea h ...
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