7563 



HYDROGRAPHIC MANUAL 



Page 696 



ground detail, but differ in size on the two sheets. Every fifth line should be accentuated to faciUtate 

 identification. The detail may then be transferred from one sheet to the other by reference to the 

 positions within these small squares. 



In order to obtain any reasonable accuracy, the squares on the smaller scale should 

 be formed by lines not more than one-eighth inch apart. "When these squares are 

 correctly drawn, they may be termed corresponding sq^mres because each square corre- 

 sponds to its respective square in terms of the ground area. 



STACK 



FiGXJEE 156.— Reduction of topography by method of squares. 



If it is desired to avoid marking up the source sheet, the squares may be drawn on 



tracing paper and laid over the detail to be transferred. The procedure is then the 



same as above. 



7563. Radial-Line Method 



Like the method of squares, this method (fig. 

 157) should not be used for transferring topographic 

 detaU to the smooth sheet. It is of most value where 

 only an approximate accuracy is needed and the 

 detaU consists only of the high-water line. It is 

 faster than the method of squares. To use the 

 method, a point common to the two surveys is selected 

 from which radial lines can be drawn to intersect the 

 general trend of the shoreline at not too acute an 

 angle. 



In practice, tracing paper is placed over the sheet with 

 the source material, and from the selected point radial lines 

 are drawn to intersect the shoreline at all salient points and 

 at enough intermediate points to permit fairly accurate 

 sketching of the detail. In the simplest case, where it is 

 desired to transfer to a scale twice as large or half as large as the original, it is merely necessary to 

 use dividers to double or halve the radial distances from the common point to the intersections 

 with the shoreline and plot the new distances along the same lines. Subsequently the intervening 



Figure 157.— Reduction of topography by 

 radial -line method. 



