PREPARATION OF THE DESIGN 77 



distance of A to P. Halve A B at C, putting in a 

 stake. Set a line D B at right angles to A B, and 

 move along this line until a point E is found in a 

 line with C and P, and E B equals A P and is the 

 distance required. 



Although it has been stated that surveying by 

 line alone leaves angles out of the question, yet it 

 is necessary to be able to set up a right angle, both 



(*> 



DIAGRAM 23. 



in taking measurements and in setting out land 

 from a plan. Three methods are possible. From 

 A on the line A B a right angle is required. (See 

 Diagram 23.) 



i. Extend B A to C so that C A = A B. Fix 

 the tape at B and C giving considerably more 

 than the length B C, if B C is 30 ft. let the tape 

 run to 50. Take the middle of the tape, in this 

 case at 25 ft., and pull it out taut, put in a peg 

 at 25 and from the apex of the triangle so formed 

 to A is a right angle. This is a convenient method 

 of setting paths at right angles to buildings where 

 a base line already exists. By making two trian- 



