HEIGHT MEASURING. 



19 



Only the latter are really useful for forest operations. Most 

 in use are those by Faustman, Weise, and Christen. Others 

 are those by Hossfeld, Winkler, Bose, and Klaussner. A very 

 simple instrument is the measuring board by Konig. 



Measurements made with the above-mentioned hypsometers 

 are liable to yield inaccurate results, owing to the following 

 causes : — 



(1.) Inaccurate reading owing to the unsteadiness of the 

 plumb line in windy weather, or in consequence of a 

 shaky hand. 



(•2.) Inaccurate measurement of the base line. 



(8.) Slanting position of the tree. 



Other things being equal, the most accurate results are 

 obtained, if the distance of the observer from the tree equals 

 the height of the tree. 



The inaccuracy of the better hypsometers does not exceed 

 2 per cent, of the height of the tree. 



h. T'rigonomctrical HelgJit Measuring. 



This is based upon the measurement of the angles of eleva- 

 tion and depression indicated by rays running from the eye of 



#: 



■■X 



Fi<?. 12. 



-i 



the observer to the top and foot of the tree. In /\ B C D 

 (Fig. 12)- BC = DCx tan. h. 



c2 



