PROFILE PLOTTING.— Make profile plottingon regular profile paper that has ruled horizontaland vertical parallel lines, as shown in figure14-22. Vertical lines are spaced 1/4 or 1/2 in.apart; horizontal lines are spaced 1/20 or 1/10 in.apart. In figure 14-22, the vertical lines on theoriginal paper (reduced in size for reproductionin this book) were 1/4 in. apart. On the originalpaper, there was a horizontal line at every 1/20-in.interval; for the sake of clarity, only those at every1/4-in. interval have been reproduced.For the first consideration in profile plotting,select suitable horizontal and vertical scalesfor the profile paper. The suitability of scalesvaries with the character of the ground and otherfactors. In figure 14-22, the horizontal scaleused was 1 in. = 400 ft, and the vertical scaleused was 1 in. = 20 ft (reduced in size forreproduction in this book). Normally, to facilitatethe plan plotting, choose scales that are propor-tional numbers in multiples of ten, such as thosegiven above (H, 1 in. = 400 ft, and V, 1 in. = 20 ft).Write the stations and elevations, as shown infigure 14-22.Plot the profile, usually from profile levelnotes, though you may plot it from the elevationsobtained from the contour lines. Assume thatprofile level notes indicate the following center-line elevations at the following stations from5 + 00 through 15 + 00.As you can see, an elevation was taken at everyfull station and also at every plus where there wasa significant change in elevation. Can you see nowhow important it is to follow this last procedure?If an elevation had not been taken at 8 + 75, thedrop that exists between 8 + 00 and 9 + 00 wouldnot show on the profile.Check through the listed elevations, and seehow each of them was plotted as a point locatedwhere a vertical line indicating the station inter-sected a horizontal line indicating the elevationof that station. Note, too, that usually stationsare labeled where the line crosses highways,streams, and railroads.Besides the profile of the existing terrain, thevertical tangents of the proposed highway centerline have been plotted. The end elevation for eachof these (that is, the elevations of points ofvertical intersection [PVI]) were determined by thedesign engineers. Various circumstances wereconsidered. One of the important ones wasfacilitating, as much as possible, the filling of eachdepression with an approximately equal volumeof cut taken from a nearby hump or from twonearby humps.The gradient, in terms of percentage of slope(total rise or fall in feet per 100 horizontal feet),is marked on each of the vertical tangents. Thispercentage is computed for a tangent as follows.For the tangent running from station 6 + 00 tostation 18 + 00, the total rise is the difference inelevation, orThe horizontal distance between the stations is1,200 ft. The percentage of slope, then, is thevalue of x in the equationFor a tangent running from station 18 + 00to station 26 + 00, the total slope downward isthe difference in elevation, orThe distance between the stations is 800 ft. Thepercentage of slope then is the value of x in theequation14-28

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