METHODS OF CONSTRUCTING TAPER TABLES 203 



A set of curves (the third) will therefore be made from all trees of 

 the same D.B.H., such as the 14-inch class. In this set the independent 

 variable which is plotted on the horizontal scale is the total height of 

 the tree in feet. The dependent variable is diameter of taper at upper 

 points, as in all the graphs used in this method. 



The set of points, which is transferred from curves in Fig. 33 and falls in the 

 vertical column above the height of the tree, is the diameter of a 14-inch tree, 

 90 feet high, at each taper measurement, the larger diameters, beginning with 

 D.B.H., falling highest in the column. 



After each series of points for 14-inch trees, representing trees of different total 

 heights as 80, 70, 60 and 50 feet, has been taken from the separate sets of curves 

 prepared in step 2, for each of these height classes, and plotted successively on 

 Fig. 34, the points representing diameters at the same height, e.g., at 8 feet from 

 stump, are connected. 



Irregularities in the resultant curves show departure in form for one height 

 class as compared with others. By smoothing out these curves, the tapers of trees 

 of different height classes are harmonized. The scale used in this set is 5 feet 

 per inch for the horizontal scale, 2 inches per inch for the vertical scale. In Fig. 34 

 only the resultant harmonized values are shown 



Fourth Set of Curves, Tapers Re-plotted on Basis of D.B. H. To utilize 

 the data from Fig. 34 the values may be read off direct, forming tables, 

 but it is customary to have these tables classified by height classes, 

 as in Fig. 33 instead of by diameter classes. To bring together these 

 values, the curved values for the separate diameters may again be assem- 

 bled on one sheet as in Fig. 33 with a separate sheet for each height, 

 diameters on the horizontal scale, upper diameters on the vertical scale, 

 and a curve for each fixed height above the stump. This replotting 

 should still further iron out any irregularities in taper values. The 

 taper table can be read from this set direct, but only for the fixed heights 

 given in the table, e.g., for 8, 16, 24 feet, etc. 



Final Set of Curves, Tapers Replotted on Basis of Height above Stump. 

 One further step completes the curves of form, by restoring them to 

 the shape of the separate trees as shown in Fig. 32. In this final step the 

 values are plotted as for Fig. 35, with separate graphs for height classes, 

 height above ground on the horizontal scale, upper diameter or tapers 

 on the vertical scale and a curve for each diameter class. 



The form of such a set of tapefs for universal use should be graphic, 

 thus showing the upper diameter at every point on the stem. From 

 this set of graphs, board-foot volume tables for any log rule, length of 

 log; upper diameter limit or stump height, cubic volume, number and 

 dimensions of ties, poles or other piece products, can be determined. 

 It is apparently a universal basis for the construction of volume tables, 

 and while the number and diversity of such tables would remain as 

 great as ever, the field work of gathering data on form or volume would 



