METHODS OF CONSTRUCTING TAPER TABLES 



201 



To plot this second set of curves the values for a given tree, or set of tapers, 

 are transferred to this new sheet, in which process the strip method described in 

 § 141 is most convenient. 

 The diameter of upper 

 tapers diminishes with in- 

 creasing height; each tree 

 is plotted in a single 

 vertical column, with 

 the D.B.H. at the top. 



The D.B.H. column 

 must be that of the 

 actual average D.B.H., 

 e.g., 14.4 inches, not 14 

 inches. When each set 

 of values has been 

 transferred and plotted 

 above its respective 

 D.B.H., the points rep- 

 resenting equal heights 

 above stump are con- 

 nected by lines. The 

 guide line for this set 

 of curves is a line drawn 

 at 45° angle whose value 

 would be D.I.B.= 

 D.B.H. For any tree, 

 the D.I.B. at D.B.H. 

 is less than the D.O.B., 

 and at upper points, 

 D.I.B. is still less; hence 

 all points above D.B.H. 

 will fall below this line. 



Regular forms such 

 as are shown in Fig. 35 

 could be drawn directly 

 on Fig. 32 guided by 

 the original averages, 

 which will usually be 

 far more regular in 

 themselves than those 

 shown in the diagram. 

 But the desired shifting 

 of the basis to exact 

 D.B.H., e.g., 14 inches 

 instead of 14.4 inches, 

 and the far greater ac- 

 curacy in harmonizing 

 tapers secured by plot- 

 ting (Fig. 33) makes the 

 method of plotting a 

 second set of curves 

 almost obligatory. 



16 17 18 19 20 21 22 

 D.B.H., Inches 



Fig. 33. — Tapers of the four trees shown in Fig. 32, plot- 

 ted on basis of D.B.H. for each 8-foot point, and 

 results evened off by curves. Separate curves are 

 made for each height above stump. Effect is to 

 reduce the irregularities of form in Fig. 32. 



