CHAPTER III 



HORIZONTAL LOCATION 



The primary control or geometric work is, in the ordinary case, effected 

 by triahgulation. Wherever this is not practicable or not economic, resort 

 is had to what is known as primary traversing, but wherever the country pre- 

 sents sufficient relief for the purpose, triangulation is employed, as it is more 

 accurate and cheaper. In some parts of the country triangulation of suffi- 

 ciently accurate character for controlling the map has been executed by 

 other organizations, notably by the U. S. Coast and Geodetic Survey, and the 

 U. S. Lake Survey. Wherever such triangulation is available, the results 

 should be adopted and utilized for the control of the maps. 



PARTY ORGANIZATION. 



The primary triangulation is generally carried on by a special party. 

 It is, however, on some accounts and under certain circumstances, economi- 

 cal -and advisable that all the work be done by one and the same party. 

 The disadvantage is that it divides the time and attention of the topographer, 

 requiring him to turn his attention from one thing to another; the advan- 

 tage, that it insures the selection of such points as are needed by the 

 topographer for carrying forward the work. If the work is done by a special 

 party, the points selected are more likely to be chosen on account of their 

 forming good figures in the triangulation, than on account of their conve- 

 nience and usefulness to the topographer. The secondary triangulation, the 

 traversing, and the sketching are usually carried on by different men, but 

 under a single party organization. The sketching is done by the chief of 

 party, the secondary triangulation and height measurement by his most 

 experienced assistant, while the traversing, with height measurement, is done 

 by the other assistants. 



