Journal . RAILWAY SURVEYING BY PHOTOGKAPHY 205. 206 RAILWAY SURVEYING BY PHOTOGRAPHY. Comparisons such as are called for in this connection present nodifficulty and occasion but little trouble. The photographs having been contoured, with whatever close-ness is stipulated for by the paymaster of the undertaking, arenow ready to be placed upon the plotting board. The principleof the plotting operation may be defined loosely in a word bysaying that it is effected by means of a modified is to say, there is a spotting point which is carried over thephotograph and deposited on any sp
Journal . RAILWAY SURVEYING BY PHOTOGKAPHY 205. 206 RAILWAY SURVEYING BY PHOTOGRAPHY. Comparisons such as are called for in this connection present nodifficulty and occasion but little trouble. The photographs having been contoured, with whatever close-ness is stipulated for by the paymaster of the undertaking, arenow ready to be placed upon the plotting board. The principleof the plotting operation may be defined loosely in a word bysaying that it is effected by means of a modified is to say, there is a spotting point which is carried over thephotograph and deposited on any spot which it is desired to plot,and a spotting arm for carrying the spotting point ; while, con-nected with this spotting arm, so as to move parallel with it, is aplotting arm carrying, or controlling, a drawing point or prickingpoint by which the plotting is actually done upon the plan. Thephotograph being mounted in due position on the board, thisparallel movement of the two radial arms suffices to produce acorrect plan, provided that the rad
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Keywords: ., bookcentury1800, bookdecade186, bookpublisherlondon, bookyear1861
