Figure 27-14. Contour map of function 



( y 2 + 1) ( x 2 _|_ y 2 + 1) l/ 2 ( x 2 + y2 + 1) l/ 2 



Anomalies Measured with the Airborne Magnetometer 



The airborne magnetometer measures the component of the local anomaly 

 in the direction of the earth's total magnetic field. Since the total field is the 

 sum of the main field and the field arising from magnetized bodies near the 

 surface of the earth, the direction of the total field is changed in the neighbor- 

 hood of these bodies so that the direction of the measured anomaly component 

 does not remain fixed with respect to a given coordinate system. 



The same thing may be said in regard to the gravity meter. It measures 

 the component of the anomaly in the direction of the earth's total gravitational 

 field whose direction is influenced slightly by the local anomaly one may be 



607 



