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Published in Paul F. McCombie, Jean-Claude Morel, Denis Garnier, Drystone Retaining Walls, 2015
Paul F. McCombie, Jean-Claude Morel, Denis Garnier
Working with tape measures is easiest with clear access to the top of the wall as well as to the ground in front of it. Then a plumb-bob (a line with a weight on the end) can be hung from a piece of timber projecting from the top of the wall, with the weight set to the toe, or a distance in front of the toe if a bulge must be accommodated. Then horizontal offsets from the line to the wall face may be measured at measured heights to determine the face profile. A vertically placed levelling staff (Figure 6.2) held to the projecting timber would assist this process, and for higher structures a ladder may be needed.
Scotland’s tall chimneys. By moses jenkins
Published in The International Journal for the History of Engineering & Technology, 2022
Jenkins is a brickwork expert with a Ph D on brickwork in Scotland. He makes the point that Scottish bricklayers were among the best in the world and built tall chimneys which set world records. The brickwork of industrial chimneys is thicker at the base and becomes progressively thinner towards the top. To achieve the required ‘battered’ exterior surface some specialised items of equipment were in use. The first of these was the battering plumb rule, one side being vertical with the other at an angle according to the slope required. A line with a plumb bob was hung close to the vertical side. The second was a profile made of timber that matched the required slope of the wall. The profile was set up against the wall as it was being built to ensure that it was rising steadily without irregularities.
The location of the Pink and White Terraces of Lake Rotomahana, New Zealand
Published in Journal of the Royal Society of New Zealand, 2019
Visual alignments of ground features in landscape photos replicate the actual visual alignments on the ground as the human eye sees them from the camera location. The replication is close to exact irrespective of the specifications of the lens and camera because the alignments are dictated by the camera location and parallax (see Appendix 1, Figures A1.1, A1.2, A1.3). Sightlines within a photo replicate the alignment of ground features you would see if you stood at the camera location and suspended a plumb bob line at arm’s length in front of you and closed one eye to obtain the monocular vision of a camera lens (which also eliminates any apparent shift in ground feature alignments due to parallax). The ground features aligned behind the plumb bob line are those aligned in the photo behind a vertical line drawn through the appropriate part of the photo. The plumb bob line is equivalent to a theodolite sighting of the same alignment of ground features from the same viewing location.
Quantification of desiccation cracks using image analysis technique
Published in International Journal of Geotechnical Engineering, 2018
S. P. Singh, S. Rout, A. Tiwari
To capture the surface cracks and specimen shrinkage, a high resolution (72dpi) digital camera (Canon EOS 60D- pic size 18 MP) is installed on a platform at a fixed height of 50 cm from the specimen. Lakshmikantha et al. (2009), Oren et al. (2006) and Puppala et al. (2004) have adopted a similar technique for capturing images and analysis of desiccation cracks in soil. Black paper is placed on the base of the mould below the sample to avert the white light reflection. In this experimental work, plumb-bob is used to transfer the centre of the camera to the platform that holds specimens. This is adopted to ensure that the camera is vertical to the specimen surface. For this specific position of the camera and the specimen, the captured image is calibrated against a known value. The internal diameter of the mould is used as reference to calibrate the image. The overall set-up is shown in Fig. 2. The above specified camera is directly connected to personal computer (PC) through data cable in order to expedite the capturing of still photographs and subsequently software like ImageJ and Matlab programming tool is used for quantification of cracks. ImageJ is an open source image processing program designed for analysing of scientific multidimensional images. There is many more command operator on menu bar of ImageJ software which is called ImageJ function.