Archaeology Underwater: The NAS Guide to Principles and Practice
PHOTOGRAPHY 75 in publications. A selection of chosen artefacts can also be photographed at a higher image size and quality/ res ...
76 PHOTOGRAPHY port and the flat port. The dome port requires little focus adjustment once set, and the lens behind it retains i ...
PHOTOGRAPHY 77 Scales: Underwater scales should ideally be matt yellow and black. These are used for a variety of shots but main ...
78 PHOTOGRAPHY ‘Radius’ 1.2 and ‘Threshold’ 0. For images between 10 and 30 megabytes, ‘Amount’ 150, ‘Radius’ 1.5 and ‘Threshold ...
PHOTOGRAPHY 79 taken with a digital camera), and stitched together in the digital darkroom. The alternative is to use a digital ...
80 PHOTOGRAPHY and if appropriate a copyright statement can be added at the end. This section concentrates on the use of camcord ...
PHOTOGRAPHY 81 focus manually, then zoom out and compose the shot. However, focusing under water is best achieved manually becau ...
82 PHOTOGRAPHY computer-based editing. Computer-based editing is currently the preferred method but it does require a high-speci ...
imations of the earth’s shape are known as spheroids (or ellipsoids). Different national and international mapping systems use d ...
84 POSITION-FIXING Geographical Coordinates Conventional marine chart coordinates are geographical coordinates and are described ...
POSITION-FIXING 85 different datum with a different central meridian value and there is no overlap between zones. It is importan ...
86 POSITION-FIXING Accuracy Accuracy provides an indication of the quality of mea- surements and hence a position. In chapter 14 ...
POSITION-FIXING 87 Methods of Position-Fixing Horizontal sextant angles The sextant is one of the most useful optical position-f ...
88 POSITION-FIXING Position-fixing using horizontal sextant angles can be accurate to within 1 m radius in ideal conditions, but ...
POSITION-FIXING 89 relationship to potential sources of deviation often changes each time it is used, making correction factors ...
90 POSITION-FIXING intersection when plotted (figure 11.8). A third transit will act as a check to see whether the observed feat ...
POSITION-FIXING 91 Theodolite, electronic distance measurement, total stations The theodolite is an optical measuring tool that ...
92 POSITION-FIXING data-logger (plate 11.1). The data is stored on an electronic medium, or downloaded onto a PC, or indeed both ...
POSITION-FIXING 93 Loran C, were initially used in conjunction with GPS. They have now been almost entirely phased out and will ...
94 POSITION-FIXING so it can use them to correct its measurements. The corrections are only relevant to those satellites used in ...
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