494 Transactions. — Miscellaneous. 



page 184, I wrote, " When it was made, the triangulation 

 met the requirements of the day, for its limit of error was 

 mostly well below that introduced by the old Gunter's chain. 

 Of late years this position has been reversed by the use of the 

 steel band, with the result that ordinary traverse surveys often 

 now possess a higher degree of accuracy than the triangula- 

 tion which is supposed to govern them. Where close settle- 

 ment has spread, and on level land, many trig, stations have 

 become useless owing to buildings and plantations, and they 

 require to be supplemented by standard marks at reasonable 

 intervals, which would cost a trifle compared to the tax which 

 the want of them now levies on the public." I may empha- 

 size this by stating that many trig, stations have disappeared 

 entirely, and that the number missing is on the increase, 

 through neglect to protect or to renew the original marks. 



In addition to the " chain of triangles " already quoted, 

 standard bearings have been carried from one end of the 

 colony to the other, from principal stations ten to twenty 

 miles apart; so that our triangulation "bearings" are 

 fairly good, while our ''distances" are unreliable. Any so- 

 called major triangulation w 7 e possess is but an overriding set 

 of large triangles, the sides of which have been calculated 

 from our faulty minor triangulation, and which necessarily 

 contain its cumulative error. 



The accuracy of lineal measurement with the steel band 

 when used with care, but without any attempts at high ex- 

 actitude, is well within 2 links per mile ; that of angular 

 measurements is not so close, but " bearing " and " distance " 

 combined keep our field surveys to about a 2-link limit, 

 while the accuracy of our triangulation is certainly no greater, 

 on the average, than that of our ordinary field-work. As all 

 careful surveyors check their work in itself, the chief use of 

 the present triangulation is to supply the true bearing and 

 a nominal " position value" to which to refer the work. In 

 speaking of "accuracy of lineal measurement," I mean its 

 approach to coincidence with the official standard chain of 

 the district. These standard chains were laid down by the 

 several provincial authorities with such rude appliances as 

 were then available, and apparently on the abolition 

 of the provinces they were not compared with each 

 other, but were assumed to be similar. Recently it came 

 to my knowledge that differences existed, and as a result 

 of comparison between them and with Sydney I find that 

 Wellington and one other are about ^in. short of Sydney 

 standard, the eight other standards being nearly -^in. longer 

 than Sydney. In other words, the difference between our 

 longest and shortest official standard amounts to about 3 links 

 per mile — no two of our standards agree — and the Sydney 



