COMPUTATION AND OFFICE WORK 



33 



that his E and W departures balance, hence he should be 

 in line. The difference between northing and southing 

 gives him the distance. He may then set a second post, 

 add the distance to his previous chainage, and proceed with 

 his survey. 



COMPUTED TRAVERSE 



When a closed survey is made, that is to say, when a sur- 

 veyor starts and finishes at the same point, it is evident that 

 its (+) and ( ) departures should be equal, also its (+) 

 and ( ) latitudes. Owing to the errors unavoidable in 

 survey work it is very seldom that they do so reckon up 

 exactly. The amount by which the two ends fail to meet, 

 whether plotted or reckoned, is the error of closure, and the 

 percentage of error is the ratio of this distance to the total 

 length of the survey. A certain percentage of this error, 

 say 1 in 500 or 1 in 300, may be allowable in an ordinary 

 woods survey. For plotting and for area, however, it may 

 be desirable to distribute the error through the different 

 courses, and this, when the traverse has been reckoned out, 

 is readily done. The error in both latitude and departure 

 is usually distributed to the different courses in proportion 

 to the length of each, but if any course was more difficult of 

 chainage than the others, it may be given extra weight in 



