THE USE OF CORRECTION FACTORS FOR VOLUME 



293 



~ ^~H^ 



The problem of combining a large per cent of area on a heavily 

 timbered type, as the cove type, with a small per cent elsewhere, has 

 been solved here by running strips across the entire area, embracing 

 the minimum per cent. Where these strips cross the cove types, points 

 are marked on the ground which serve to tie in the strips run through 

 the coves. Where 100 per cent is not estimated, a plan of running 

 strips in a zigzag course from one boundary to the others of the type 

 through these coves has been adopted. The more acute the angle 

 between two courses and the 

 more nearly parallel the result- 

 ant strips, the greater the per 

 cent of the type included. 



229. The Use of Correction 

 Factors for Volume. The pur- 

 pose of all estimates is to secure 

 the actual volume of timber on 

 the entire tract as accurately 

 and inexpensively as possible. 

 In systems of covering partial 

 areas, even after the probable 

 error has been reduced by adopt- 

 ing subdivisions based on type 

 or forest cover and site, there 

 remains a final possibility that 

 the average stand per acre within 



the type differs from that secured by the methods employed. 1 The older 

 and more diversified a stand, the greater will be its irregularity of stocking, 

 and the greater the necessity for accuracy. Can this accuracy be still 

 further improved? A correction of an average, mechanically obtained, 

 rests upon the assumption of definite knowledge that this average is 

 wrong, and the ability to determine approximately how much it is in 

 error. Since the timber on the area lying outside the measured and 

 estimated strips is neither counted nor measured, the impression that 

 the average is wrong depends upon the ability of the cruiser to estimate 

 or size up timber by the eye and to compare it ocularly as a whole with 

 the stand upon the strip which he has measured. This comparison 

 is useless unless enough of the remaining timber can be seen so that 

 it is practically certain that the average stand on the whole remaining 

 area is greater, or less than that measured on the strips. Where strips 

 are narrow and run at wide intervals, it is impossible to arrive at this 

 judgment and no reliable correction can be made by eye. 



1 Errors in Estimating Timber, Louis Margolin, Forestry Quarterly, Vol. XII, 

 1914, p. 167. 



Fig. 62. — Method of running strips to cover 

 an additional 20 per cent of area in heavily 

 timbered type, on basis of original 5 per 

 cent estimate for entire area. Strips 8 rods 

 wide. 



