376 Forestry Quarterly. 



west tier of sections. The errors made in measuring north and 

 south are thrown into the northern tier of sections. 



The aim of the survey was to approach as closely as possible to 

 the ideal theoretical township. For the purpose of the topo- 

 grapher it is just as well to lose sight of this object of the survey 

 entirely and treat the whole survey as a system of traverse lines. 

 If this is done the section corners will not be thought of as monu- 

 ments one mile apart, but will be treated as accurate geometric 

 locations. 



The topographer will treat these points upon the base map not 

 as corners of sections, but as points of control accurately located 

 by angle and distance from a definite starting point, i. e., the 

 initial point of the survey. Such a system of points can serve 

 every purpose of a triangulation network. 



Accepting this network of control as sufficiently accurate for 

 the purpose of the Forest Service surveys, the primary control 

 can be extended into neighboring unsurveyed townships while 

 working the townships surveyed by the U. S. Rectangular Land 

 Survey. 



Mountain peaks can be located accurately, and their location 

 plotted. These peaks now become points of control and they 

 are definitely tied to land comers. 



In using this method it is necessary to do all the work in sur- 

 veyed townships first. By working the unsurveyed territory last 

 a greater number of primary points of control can be obtained. 

 It is obvious that the mountain peaks in the adjoining unsurveyed 

 country will not be visible from every section corner, or more than 

 a few points along the base lines run by the base line crews in 

 the surveyed townships, but the parties rerunning the old traverse 

 line (section lines) of the Rectangular Survey will be able to 

 locate all necessary points of control while completing the work 

 in the surveyed townships. Base line crews can take sights from 

 intermediate stations along the section lines, since all the distances 

 are being accurately measured either by chains or stadia, and the 

 stations are accurate locations. If necessary short traverse lines 

 can be run commanding points and sights taken from these loca- 

 tions. 



When the work is to be begun in the unsurveyed township, the 

 topographer has already secured a base plat of the area with some 



