154 



A MANUAL OF TOPOGRAPHIC METHODS. 



Table IX. — For computing differences of altitude from angles of elevation or depression (applicable to 



scale 1:45000). 



[Prepared by ll- S. W Iward.] 



...... r .... , C 4~ Dfti + h., tor aimlis of i-lt-vation. 



Difference of altitude = \ 1 J)ft | | ^ fol . .,„„,,.„ , )t ,,„,, ression . 



, inch each 



D — distance in scale divisions j 

 ii tor < urvature and refraction. 

 Argument for h y is a; argument for h 2 is 1). 



angle of elevation or depression; hi = 75 feet X tan a; /t 2 



