4 PRELIMINARY MEASUREMENTS 



Using the calipers as a standard now fmd the ])er('entage of error by 

 divifUng tlie (HtTerenee ()l)tained V)y the total number of eaUpered 

 inches. 



Comment on the comparative efhciency of the various methods 

 and instruments as to accuracy, portabihty, etc. 

 3. In order to develop proficiency in estimating diameters by eye now 

 make an ocular estimate of a large number of trees, checking each 

 estimate with the calipers. 



D. References. Numbers 1, 2, 3, 5, 6, and 10. 



Note. — All numbers to references in this and succeeding problems refer to 

 Bibliography in the Appendix. 



PROBLEM 3. (Field.) The Determination of the Heights of Standing 

 Trees. 



Explanation. — The object of this problem is to give practice in estimating 

 the heights of standing trees by eye and other rough methods, and by means 

 of hypsometers, and to compare the efficiency of the various methods. 



Directions. 



A. Parties. — Students will work in two-man parties, alternating in the use 



of instruments and in tallying results. 



B. Equipment Required. — All the different types of hypsometers available, 



a 100-foot tape, and notebook supplied with Form 1 . 



C. Method of Procedure. 



1. Select a tree standing in the open and measure its height accurately 



by means of a transit or other accurate method designated by the 

 instructor. In using the transit, set up at any convenient 

 horizontal distance measured from the tree, and read the vertical 

 angle to the top of the tree. With a table of natural tangents of 

 a right angle triangle compute the height of the tree above the 

 level of the center of instrument. In a similar manner obtain the 

 height below this level and add the two for the total height of the 

 tree. 



2. Measure this tree by the following rough methods: {a) shadow, 



(6) two-pole, (c) prostrate, and {d) with single pole, and with 

 as many of the following hypsometers as are available: (e) Klauss- 

 ner, (/) Faustman, {(j) Weisc, (/?) Winkler, {i) Christen, (j) 

 Brandis, (A:) Goulicr, (/) omnimeter, (w) Abney level, (n) Barbow 

 compass, (o) Forest Service Standard, (p) Forest Service Compass. 

 (See note for description of rough methods.) 



