SURVEYING 



31 



read. The use of instruments for measuring angles will be 

 described later. If measurements have been made to 

 determine angles, these angles may be laid out with the aid 

 of the compass, setting this instrument with the scale and 

 describing circles whose radius is equal to the length of the 

 sides of the triangle. The map should first be made with a 

 pencil, and then, after every feature has been drawn, should 

 be inked in. 



Common Topographical Signs. A topographical map is 

 one which gives the general character of the land surface, 



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Orchard. DeciduousTrees. Evergree 



Fig. 13. Conventional topographical signs. 



showing where there are roads, buildings, forests, swamps, 

 etc. To facilitate the making of such maps, it is customary 

 to use certain symbols or methods of representing certain 

 conditions of the surface. A general use of certain symbols 

 to indicate certain things has resulted in their being known 



