VOLUME TABLE IN BOARD FEET BASED ON D.B.H. 



35 



C. Discussion. 



1. What is the difference between a table of form factors and a volume 



table? 



2. What is the difference in their uses? 



3. Which is the more practical for ordinary timber estimating? 



PROBLEM 19. (Field.) The Construction of a Merchantable Volume 

 Table in Board Feet Based on D.B.H. and Number of IQ-Foot Logs by 

 THE Frustum Form Factor Method. 



Explanation. — A method of constructing volume tables based on D.B.H. 

 and log lengths which much lessens the office work involved and which will 

 give a better table with a lesser number of trees has been devised by Mr. 

 Donald Bruce and is described by him in the Forestry Quarterly, Volume X, 

 Number 2 and in the Proceedings of the Society of American Foresters, 

 Volume VIII, Number 3. This method has not gained universal use and 

 its accuracy compared with the usual method of constructing volume tables 

 has not been entirely established. Several tests have, however, shown that 

 excellent results can be obtained with the method. The following problem 

 will demonstrate this method of constructing a volume table. 



Directions: 



A. Data Required. — About 25 trees will be required for Method I and 100 



or more for Method II. Use data collected in Problem 6, or trees of 

 different sizes w^hich show the volumes of boles in board feet measured 

 in 16-foot lengths to an 8-inch diameter in the tops selected at random 

 from Data Series I. 



B. Method of Procedure. 



Method I. To construct a volume table with a small number of trees. 

 1. Tabulate the sizes of the trees to be used in this problem according to 

 the following form : 



D.B.H. 

 Inches 



No. 16-ft. Volume 



Logs B.M. 



to 8" Top j to 8" Top 

 Diameter ' Diameter 



Frustum 

 Form 

 Factor 



Compute the frustum form factor for each tree by dividing the volume 

 of the tree by the volume of the corresponding frustum of a cone as 

 secured from the table of frustums of cones in the Appendi.x (Table 

 IV). Interpolate in this table the volumes for diameters breast 

 high to 0.1 inch and lengths to the nearest ^ of a 16-foot log. 



