CHAPTER XX 

 METHODS OF TIMBER ESTIMATING 



213. The Importance of Area Determination in Timber Estimating. 

 Except in a few instances where every tree on a tract is separately 

 measured, all methods of timber estimating depend upon the principle 

 of applying the results obtained on part of an area to the entire area, 

 or on small portions of an area to larger subdivisions. Any error in 

 determining the total area included within the boundaries of a tract, 

 or the correct area of any subdivision made within it, will incur a cor- 

 responding error in applying the results of the estimated portion to the 

 whole. The separation of timbered from non-timbered areas is an 

 example. If the average stand of the timbered portion is correctly 

 found, but its area is estimated to be 10 per cent greater than it actually 

 is, an error of plus 10 per cent is incurred in the estimate. Correct 

 determination of areas of the tract and its timbered subdivisions is 

 the first consideration in the field work of timber estimating and counts 

 for fully half in the total scale of accuracy. 



The first essential is to locate and determine definitely the boundaries 

 of the area to be estimated. Where the tract lies in regions subdivided 

 by a rectangular system of government surveys this is not ordinarily 

 difficult. The area may be approximately located with sufficient 

 exactness for the work. Even here it is necessary to identify the 

 section corners and sometimes to re-run the lines if time permits. In 

 other regions where the land surveys follow an irregular pattern, the 

 identification of the corners and lines is best accomplished by the aid 

 of some local resident who is familiar with these bounds. The retrac- 

 ing and mapping of the boundaries of a property is an essential step 

 in management, but its cost is not properly chargeable against the item 

 of timber estimating alone. 



If methods are used by which 100 per cent of the timber is estimated, 

 the total stand can be obtained independent of the actual area or shape 

 of the tract provided only that all of the trees upon it are counted and 

 their contents determined. When for a 100 per cent estimate is sub- 

 stituted an estimate covering only a part of the tract, the cruiser requires 

 a knowledge of its shape and size. In the rectangular system of surveys 

 most of the subdivisions are square and the smallest unit commonly 



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