34 THE CONSTRUCTION OF VOLUME TABLES 



3. What is the difference in the data required for the construction of a 



table based on D.B.H. only and one based on D.B.H. and total 

 heights? 



4. Which of the two tables would be the more accurate and why? Which 



would be easier to use? 



5. How many trees would ordinarily be considered the minimum for a 



good D.B.H. only volume table? For a D.B.H. and total height 

 table? 



6. Outline stej) by step and in detail the nu^thod of procedure in a manner 



similar to that used in Problem 17 for making a table based on 

 D.B.H. and number of 16-foot logs. 



7. What are the chief details in which the construction of a table based 



on D.B.H. and merchantable lengths differ from the method of 

 procedure outlined in Question 6? 



8. Describe briefly how a cordwood table based on D.B.H. would be 



constructed. 



9. Describe briefly how a tie table based on D.B.H. would be constructed. 



PROBLEM 18. (Office.) The Construction of a Table of Stem Form 

 Factors Based on D.B.H . Only. 



Explanation: The object of this problem is to illustrate the method of 

 constructing a table of form factors and to show the difference between such 

 a table and a volume table. 



Directions: 



A. Data Required. Use the data collected in Problem 6. 



B. Method of Procedure. 



1. First compute the full stem volumes of the trees in cubic feet as 



explained in Problem 13, Illustration I. 



2. Divide the computed volume of each tree by the cubic contents of a 



cylinder whose diameter is the same as the D.B.H. of the tree, and 

 whose height is equal to the total height of the tree. Call the 

 results the "form factor fractions." For determining the contents 

 of the respective cylinders use the tables of Basal Areas in the 

 Appendix and multiply by the heights. 



3. From this point on, the method of constructing the tajjie will be the 



same, step by step, as outlined for Problem 16, except that the 

 expression "form factor fraction" is used in place of "volume in 

 board feet" throughout the exercise. 



Note. — For rough work the Schiffel formula may be used for securing the 

 form factor directly without the necessity of first finding the cubic volume and 

 then dividing this volume by the volume of a cylinder. By the Schiffel formula 

 the form factor of a tree is equal to 0.16 + 0.GGXQ2 where Q is the form quotient, 

 which is the D.M.H. divided by the D.B.H., where the D.M.H. equals the diam- 

 eter at the middle height of the tree. 



