Chap. 3] 



MEASUREMENT PROCEDURES 



41 



11. ARRANGEMENT OF OBSERVATION POINTS WITH 

 RELATION TO GEOLOGIC OBJECTS 



In geophysical exploration, the objects of detection are geologic struc- 

 tures or mineral deposits, and the detecting units are usually spread out 

 along the earth's surface. This is done (1) to determine the variation of 



Table 3 

 PROCEDURES OF MEASUREMENT IN GEOPHYSICAL EXPLORATION 



the physical quantities measured between points and to obtain a clue to the 

 presence or absence of a geologic body; and (2) to determine the depth of a 

 formation if it remains in horizontal position throughout the length of a 

 profile. The first operation falls under the heading of geophysical ma-p- 

 ping; the second is known as geophysical sounding. By far the greater 

 portion of all geophysical work is done by means of surveying processes 

 on land, in shallow water, underground, or on small-scale laboratory models 



