TIMBER ESTIMATING AND MARKETING 169 



upon the intended accuracy of the estimate. Lines run one mile 

 apart give a measurement of one and one-quarter per cent of 

 the entire area; one-half mile apart two and five- tenths per 

 cent; one-quarter mile apart five per cent; one-eighth mile ten 

 per cent, etc. However, in practice, the lines are rarely run 

 nearer than one-quarter mile, and usually two and five-tenths 

 per cent of the area is considered sufficient. By making note 

 of changes of type, topography, streams, etc., it is possible to 

 make a fairly accurate map of the tract. The areas of the 

 different types can be determined from this map. Along with 

 the survey the crew should take the height measurements of a 

 few hundred trees of the most important species, to obtain the 

 average height for each diameter class. 



When all the required valuation surveys have been secured 

 there remains a large amount of work to be done. In the first 

 place, the tally sheets are assorted according to the type of land 

 they represent. Of the 500 acres measured in the io,ooo-acre 

 tract, suppose 100 fall into the second-growth pine type, 150 

 into mixed hardwoods, 200 into second-growth spruce, and 50 

 into abandoned pasture. The sheets representing each of these 

 types are averaged together, giving an average acre for each type. 

 This shows the average number of trees of each diameter and 

 species for the type, and the contents can be obtained from 

 volume tables as discussed under A. The total volume of each 

 species is then multiplied by the number of acres in the whole 

 type, giving a total for the type. 



The valuation survey method of estimating, described above, 

 undoubtedly surpasses, for accuracy and cheapness, any other 

 method and admits of considerable variation in detail. There 

 are now forestry companies whose main business is to estimate 

 timber, and, as far as known, they all use some modification of 

 this system. 



Another method applicable for large tracts, by which the data 

 for a map are secured along with the estimate, is a combination 

 of the strip system and the circular plot method outlined under 

 B. The chief advantage of this method is that it can be done 



