AVERAGES EMPLOYED IN TIMBER ESTIMATING 



259 



A combination of these two systems may be used as follows: First plot the 

 points, then compute the mechanical averages from the plotted data by using the 

 scale as follows: For the 9-inch trees, assume the 40-foot point as 0. The 

 trees are then entered as having the weights 0, 3, 8, 8; total 19; average 4.8 plotted 

 as 5 above the 40-foot point, or an average height of 45 feet. This method com- 

 bines the advantage of visualizing the data to indicate abnormally high or low 

 trees, with a slight reduction in the work of mechanical averages. 



2. Instead of tallying the diameters of all the trees, they are merely 

 counted, but a certain fixed percentage of the total number is tallied 

 for diameter (the heights are either tallied individually or the method 



9 10 



11 12 13 

 D.B.H. Inches 



14 



15 16 IT 18 



19 



Fig. 56. — Method of constructing a curve of height based on diameter at B.H. 

 White Pine, Milford, Pike Co., Pa. 



of averages described above is applied). The volume of the average 

 tree of the per cent tallied is used to find the average volume cf the 

 numbers counted but not measured. 



In Southern longleaf pine, it is possible to count all of the trees on a tract, 

 and to tally the diameter and merchantable height of one tree in every three in 

 such a way that the trees tallied represent the mechanical average of those counted. 

 When the volume of the tallied trees is computed, it represents one-third of the 

 volume of the stand. The work of tallying has been reduced one-third and the 

 accuracy greatly increased, when considered with reference to the time required to 

 complete the work. 



3. None of the trees in the stand is tallied for either diameter or 

 height. The trees are merely counted and the cruiser then decides 

 upon the volume which will be contained in the average tree of the stand. 

 He may obtain this either through a direct guess as to volume or through 



