DETAIL SURVEYS. 891 



must exactly indicate every operation performed, no erasures 

 being- permitted under any circumstances, but if an erroneous 

 entry is made the pen should be drawn through it and the 

 correct figures entered above. Special care should be taken 

 with the field notes, both in their preparation and sub- 

 sequently, as they are the actual official records of the field 

 operations of the survey, being of far greater importance 

 than the plan afterwards prepared from them. On completion 

 of the field work the detail surveyor computes his traverses, 

 &c., applying any necessary corrections to the latitudes and 

 departures to make the coordinates of his various survey points 

 agree absolutely with those already laid down by the standard 

 survey. The original field notes, together with a tabulated 

 form showing his traverse lines, computations, amount of 

 corrections, &c., together with a sketch showing the position 

 of the co-ordinate lines and a rough plot of his traverses with 

 references to the pages of his field book. 



Draftsmen specially trained to that class of work should 

 be employed on the preparation of the plans, which should 

 be plotted on the best drawing paper. Antiquarian size, double 

 mounted, that is, two sheets of paper mounted with holland 

 Ijetween them. As rolling strains the paper and nearly always 

 injui-es the correctness of the plotting, detail plans should be 

 always kept flat. The scale generally used, 60 links to an inch, 

 is found to be suitable, because the lithographs or zincographs 

 prepared are exactly equal to 40 feet to an inch, which is a 

 convenient size for laying out engineering works, and is 

 sufficiently large for the minutest detail to be shown. Co- 

 ordinate squares often inches each are carefully laid down, each 

 coordinate line being a multii)le of six chains from the origin, 

 and the traverses are plotted on the coordinate system, the 

 protraction being only used for plotting in the radiations. By 

 tliis method all accumulation of errors in drawiug is avoided, 

 and as the square on the pajjer indicates the unit of length 

 used in the plotting of all within that square, any changes in 

 the paper caused by temperature or hygronietric conditions do 

 not affect the correctness of the plan. No colour should be 

 used on the plans except for ruling in the traverse lines and 

 radiations, the materials of which the buildings are made 

 being indicated by small letters, B. for brick, S. for stone, &c. 

 All the requisite measurements having been taken on the 

 ground it only requires conij^aratively a few computations to 

 be made to place on the plan the dimensions of all holdings 

 within the block, with their relation to the base line along 



