ERRORS IN ESTIMATING TIMBER. 

 By Louis Margoun. 



A timber estimate, at best, is an approximation of the actual 

 amount of timber on the ground. The very term "estimate" in- 

 dicates this. The accuracy of the approximation will depend on 

 the accuracy and the intensiveness of the estimate, though the 

 true error involved can never be determined because the actual 

 volume can never be determined with absolute accuracy. 



The sources of error in timber estimating may be divided into 

 three classes, as follows : 



1. Errors inherent in the method of estimating used. It stands 

 to reason that if the principles on which any system of timber 

 cruising is based are fallacious', the results obtained will be in- 

 accurate, no matter how carefully the work is done. 



2. Errors in the application of the system. The system of 

 estimating used may be sound in principle, yet if it is not ap- 

 plied accurately, the results will not be correct. Personal mis- 

 takes, carelessness and negligence, as well as errors due to the 

 use of unreliable volume tables, come under this heading. 



3. Errors involved in making an estimate on only a small part 

 of the area. Even if the system used is correct and it is ap- 

 plied carefully, there may still be errors in the estimate due to 

 the fact that the cruise does not cover an extensive enough pro- 

 portion of the area to which it is- applied and the proportion cov- 

 ered is not representative of the rest of the area. 



This paper will confine itself largely to the last mentioned 

 source of error. 



It is hardly necessary to enter here into a detailed discussion of 

 the different methods of cruising timber. With the exception of 

 a very few systems of ocular estimating, most of them are based 

 on a per cent, estimate. That is to say, only a given per cent, 

 of the area is measured and the content of the entire stand is 

 obtained by proportion. Other things being equal, the higher the 

 per cent, of the area actually measured, the more accurate, of 

 course, is the cruise. Still it is only in very rare cases' that a 

 100 per cent, estimate is practicable. The usual cruise covers 

 either 5 or 10 per cent, of the area. 



