METHODS DEPENDENT ON THE USE OF PLOTS 



285 



Measurement of trees The volume of each tree recorded directly, 



based upon the universal volume tables 



Forest types Not necessary to regard them 



Cull factor Deductions made for each tree when its 



volume is ascertained 



Correction from strip estimate for aver- 

 age stand By running 50 per cent, corrections are usually 



avoided. Where inspection reveals the 

 necessity, modifications are made in the 

 total estimate 



Separate record under this system may be made of the board-foot 

 contents and of other products, such as poles. The estimate is fre- 

 quently increased 

 to 100 per cent. 



These examples 

 are cited merely to 

 show the various 

 combinations of ele- 

 ments which go to 

 make up a system 

 of timber estimat- 

 ing. The securing 



of accuracy consists i 



in adapting the Fig. 59 



number and width 



of strips to the 



local conditions described ! 



estimated and, second, size 



estimated 



Horseshoe method of strip estimating, 

 of compassman shown by dotted line. 



Route 



to be 

 to be 

 instru- 



s, first, character of timber 

 of the smallest unit of area 

 The details of measurement, whether by eye or 

 ment, for distance or for tree dimensions, must be coordinated with 

 the volume table and with the skill and personal ability of the individ- 

 uals employed in the work. The saving in time by the substitution 

 of the eye and of ocular judgment requires dependence upon personal 

 skill. Where cruisers with sufficient experience are unobtainable, 

 accurate results may still be obtained by mechanical measurements, 

 carefully supervised and conscientiously applied. 



224. Methods Dependent on the Use of Plots Systematically 

 Spaced. In the use of plots in timber estimating, the method employed 

 depends upon whether the principle of mechanical arrangement or 

 spacing is to be observed, in order to obtain an average stand, free 

 from the element of personal judgment, or whether instead, plots are 

 to be selected by the use of judgment in an effort to obtain thereby 

 an average stand which will apply to the area as a whole. By the 

 first principle, the plot method, so-called, is merely a modification of 



