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two or more portions, or types, on each of which the stand will be 

 comparatively uniform, but so great is the local variation in stands 

 of timber that it is almost impossible even for experienced men 

 arbitrarily to pick out plots which will truly represent the average 

 stand . 



ADVANTAGE OF STRIP SURVEYS. 



The chief advantage of strip surveys is that the sample acres 

 represent a good average, inasmuch as they are run straight through 

 the forest and include whatever may be in the course, while arbi- 

 trary plots are likely to be located in the best areas and hence give 

 too large results. A second advantage of the strip survey is that 

 it may be made very rapidly and therefore many more sample areas 

 are obtained than is possible with carefully surveyed plots. The 

 third advantage is that the systematic location of the strips enables 

 the preparation of a map. 



The one disadvantage of the method is that there is always a 

 chance of error in estimating the width of the strips, but this is not 

 a serious disadvantage if the caliper men are careful. 



THE USE OF HEIGHTS IN ESTIMATING. 



Next to diameter, height is the most important factor in deter- 

 mining the merchantable contents of a tree. Mistakes in judging 

 height are easily made, especially in unfamiliar timber, or in pass- 

 ing from short to tall timber, or vice versa. 



It is customary to average the heights of trees. In methods 

 which depend on number of trees and average volumes, the cruiser 

 judges the average height, or the number of merchantable logs in his 

 average tree, by sizing up the stand during his cruise. At the most, 

 he may separate his timber into two classes large and small, or by 

 area into one or more types, and use the same average heights for 

 all trees in the class or type. 



A more accurate method of using heights in cruising is to deter- 

 mine the average heights of trees of different diameters in the fol- 

 lowing way: After the trees on a sample acre have been calipered 

 in the usual way the heights of a limited number of trees, generally 

 from three to ten for each species, of different diameters, including 

 small, medium, and large trees, are measured. The cruiser selects* 

 for measurement trees which appear to him to be of average height in 



