in this case, because each curve has two tangents ratherthan a single long chord.The coordinates of A, B, C, and D are the same asin the first example, but the coordinates of the points ofintersection (PIs) must be established from the latitudesand departures of the tangents. The computations fordetermining the tangent bearings are shown in the lowerleft of figure 7-34. When you have only the chordbearing, you can compute the tangent bearing by addingor subtracting one half of delta (A) as correct. The anglebetween the tangent and the chord equals N2.After setting coordinates on the PIs, youcross-multiply, accumulate the products, subtract thesmaller from the larger, and divide by 2, as before, to getthe area of the straight-line figure running around thetangents. You then add or subtract each external area asappropriate. In figure 7-33, you can see that the externalarea for Curve 1 is inside the parcel boundary and mustbe added, while that of Curve 2 is outside and must besubtracted. The area comes to 348,881 square feet,which is an acceptable check on the area obtained byusing segmental areas.Plotting Horizontal ControlComputations for horizontal control become greatlyclarified when you can see a plot (that is, a graphicrepresentation to scale) of the traverse on which you areworking. A glance at the plot of a closed traverse, forinstance, tells you whether you should add or subtractthe departure or the latitude of a traverse line incomputing the departure or latitude of an adjacent lineor in computing the coordinates of a station.For linear distances that are given in feet anddecimals of feet, you use the correct scale on anengineer’s scale for laying off linear distances on a plot.For plotting traverses, there are three common methods:by protractor and scale, by tangents, and by coordinates.PLOTTING ANGLES BY PROTRACTORAND SCALE.— For the traverse on which you havebeen working, the adjusted bearings and distances areas follows:Traverse LineBearingDistanceABN26°09'E285.14 feetBCS75°26'E610.26 feetCDS15°31'W720.28 feetDAN41°31'W789.96 feetFigure 7-35.—Traverse plotted by protractor-and-scale method.Figure 7-35 shows the method of how to plot thistraverse with a scale and protractor. First select a scalethat will make the plot fit on the size of your paper. Selecta convenient point on the paper for stations A and drawa light line NS, representing the meridian through thestation.AB bears N26°9'E. Set the protractor with thecentral hole on A and the 00 line at NS, and lay off26°09'E. You will have to estimate the minutes as bestyou can. Draw a line in this direction from A, and on theline measure off the length of AB (285. 14 feet) to scale.This locates station B on the plot. Draw a light lineNS through B parallel to NS through A, and representingthe meridian through station B. BC bears S75°26'E. Setthe protractor with the central hole on B and the 00 lineon NS, lay off 75°26' from the S leg of NS to the E, andmeasure off the length of BC (610.26 feet) to scale to7-24

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