Figure 7-36.—Plotting traverse lines by parallel method froma single meridian.locate C. Proceed to locate D in the same manner. Thisprocedure leaves you with a number of light meridianlines through stations on the plot. A procedure thateliminates these lines is shown in figure 7-36. Here youdraw a single meridian NS, well clear of the area of thepaper on which you intend to plot the traverse. From aconvenient point O, you layoff each of the traverse linesin the proper direction. You can then transfer thesedirections to the plot by one of the methods for drawingparallel lines.PLOTTING ANGLES FROM TANGENTS.—Sometimes instead of having bearing angles to plotfrom, you might want to plot the traverse fromdeflection angles turned in the field. The deflectionangles for the traverse you are working on are asfollows:AB to BC78°25'RBC to CD90°57'RCD to DA122°58'RDA to AB67°40'RFigure 7-37.—Plotting by tangent-offset method from deflectionangles larger than 45°.You could plot from these angles by protractor. Layoff one of the traverse lines to scale; then lay off thedirection of the next line by turning the deflection angleto the right of the firt line extension by protractor andsoon.However, the fact that you can read a protractordirectly to only the nearest 30 minutes presents aproblem. When you plot from bearings, your error inestimation of minutes applies only to a single traverseline. When you plot from deflection angles, however,the error carries on cumulatively all the way around. Forthis reason, you should use the tangent method whenyou are plotting deflection angles.Figure 7-37 shows the procedure of plottingdeflection angles larger than 45°. The direction of thestarting line is called the meridian, following aconventional procedure, that the north side of the figurebeing plotted is situated toward the top of the drawingpaper. In doing this, you might have to plot theappropriate traverse to a small scale using a protractor7-25
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