In the T column, enter -999. This is not a real TGRADS reading, but it signifies that 

 this is the first measurement on the tree and that it is a taped measurement rather 

 than a set of dendrometer readings. In the F column, 0200 is recorded- -the stump 

 diameter (o.b.) of the tree, 20.0 inches. The decimal point is understood to be between 

 the third and fourth digit of 0200. It is not written on the field form, but the com- 

 puter program assumes it to be there when the data are processed. The leading is 

 written in to fill the space. In the ±S column, 003.5 is entered. Although this is the 

 sine elevation column, the number entered here on the first row is not a sine elevation 

 because the first measurement is not a dendrometer measurement. Rather, this entry is 

 the distance in feet up the tree to the next measurement. On this tree it was 3.5 feet 

 from stump height to breast height, where the next measurement was taken. The decimal 

 point in this entry is written by the notekeeper. Leading O's are also entered as shown 

 in figure 8. 



Second Measurement 



The next measurement on the tree, which is d.b.h. measured with a tape, is re- 

 corded on the second row. For this level, four O's are entered in the T column. Diame- 

 ter at breast height, in inches and tenths, is entered on the second row in column F in 

 the same way that stump diameter was entered on the first row. For this tree, d.b.h. 

 was 17.0 inches. In the upper part of this form, 0170 is entered in the d.b.h. space. 

 In the second row of the ±S column, five consecutive O's are entered for this measure- 

 ment. This shows that the next measurement on the tree, which follows on the third 

 row, will be taken at the same height as the second measurement. 



Third Measurement 



The third measurement is d.b.h. again, but measured this time with the dendrometer. 

 Now, on the third row the T column contains, at long last, a true TGRADS reading, namely, 

 0485, entered as shown. Column F contains a true FGRADS reading, 0791, entered as 

 shown. The ±S column contains the first sine elevation reading, namely, -1680. 



Subsequent Measurements 



Dendrometer readings for the first level of measurement above breast height are 

 recorded on the fourth row. In this example, sine elevation readings are increasing 

 and continue to increase to the top of the tree. Notice also that all sine elevation 

 readings end in either or 5. This is because it is possible to estimate the instru- 

 ment reading to this degree of precision, but no closer. Even so, this is more 

 precision than the instrument was intended to give. However, if the instrument loca- 

 tion is changed, -^^ the continuous increase in sine elevation may be disrupted. As 

 figure 8 demonstrates, the FGRADS readings usually decrease as tree height increases. 

 Occasionally, FGRADS may increase slightly, but usually they decrease. After each set 

 of instrument readings is taken, the trend of FGRADS should be checked; if an increase 

 is noted, measurements should be checked before the instrument is moved. A short sec- 

 tion of a tree trunk may show negative taper, but this is fairly uncommon. The third 

 level of measurements above breast height is recorded on row 5 of this field form. A 

 2 is recorded in the box at the left of the T column to show that this row records the 

 first set of readings that will be punched into the second data card for this tree. 



Measurements are taken at irregular intervals up the stem separating portions of 

 uniform taper and grade. Readings taken at the top of the tree are recorded on line 9 

 of the field form. The TGRAD and FGRAD readings at the top of the tree are identical, 

 indicating a zero diameter. The last box on the right of the G column at the bottom of 

 the field form contains an asterisk (*) , which shows that the third punched card will be 

 the last card containing data for this tree. 



One move to a different instrument location up or down hill is permitted. 



24 



