COMPUTATION OF VOLUME OF THE TREE 161 



difference between volumes as cut and scaled, and volumes from regular 

 tapers. 



In case the study of the growth of trees at upper sections is required 

 (§ 289) either the trees will have to be felled and bucked into sections 

 of even lengths by System A or System B, or else the logs as cut by 

 System C must be accepted as the basis of this growth study. 



For total cubic volume, the taper measurements are continued 

 to the tip in either system. With slight additional cost, these extra 

 measurements taken above the merchantable top diameter limit com- 

 plete a permanent record of tree form available for future computa- 

 tion of volume for any unit or limit of merchantable sizes. 



A further modification is the addition of trirmning lengths, usually 

 standardized as i^feet in 16 feet, so that the points marked fall at 

 8.15 feet, 16.3 feet, 24.45 feet, etc. If this is done the fact should be 

 be noted on the analysis. Total cubic volume is obtained as accurately 

 by this method as by System A, and in addition, the data can be used 

 directly to determine the volume in board feet. It is therefore pref- 

 erable for most objects to System A. 



The width, single, of bark is measured at each diameter (§29), and 

 recorded as read. This width is then doubled and subtracted to 

 obtain diameter inside bark. ^ 



If the volume of sapwood is desired, this will require the sectioning 

 of the tree, and measurement of width of sap. Sapwood volume is 

 therefore most easily obtained by System C. 



The measurements are entered on a blank, of which an example 

 is shown on p. 160. 



This completes the field record. The remainder of the work is 

 performed at any time in the office. 



The crew for field measurements of volume, when the trees are 

 already felled, should consist of two to three men, one of whom records 

 the data while the others measure the tree. 



136. Computation of Volume of the Tree. For total cubic volume, 

 each section is usually computed by the Smalian or mean end fornmla 

 in which 



5 = area of large end of section in square feet; 



6 = area of small end of section in square feet; 



? = length of section in feet; 

 F = cubic volume. 



* Abbreviations are used, as follows: 



Diameter outside bark, D.O.B. 

 Diameter inside bark, D.I.B. 



