446 



HYDROGRAPHICAL SURVEYING 



[chap. XX. 



"otter" Sweep Diagram 



By observing angle between "Otter' boards and applying 

 half that angle in connection with half length of Sweep 

 to above diagram, the amount of wire that should be out 

 between machine and Otter can be seen. 



Peck lines represent half Sweep wire 



Black lines represent wire from Machine lo'Otter' board 



Example:- Let angle between Otter boards be 62 , then half angle =^31 - Angle B.A.C. 



Let length of sweep be 42 yards - 21 fms. then half sweep = lOj/^fms. = B.C. 

 Then A.B. (by referring to scale)-- 20'/j fms. 



Fig. 104. 



