south direction the y axis in the east west direction and the z axis in the direction of the earth 39 s gravitational force in such a case an azimuth angle u03b8 represents an azimuth from north and an inclination angle u03c6 represents an inclination from a horizontal plane with the sonde shown in fig3 the azimuth angle u03b8 illustrated in fig6 is obtained from the downdip angle indicated by the azimuth finder 8 and the dip u03c6 depicted in fig6 is obtained from the dip indicated by the dipmeter 10 more specifically bore hole curvature is measured by the azimuth finder 8 and dipmeter 10 and the orientation of the sonde is measured by the rotation meter 9 when an observation is make by the image pick up device the direction in which an observation is being made can be ascertained in terms of the relative positions between the photoelectric transducer elements and the reference position e set within the sonde the rotation meter 9 is for measuring the orientation of the sonde reference position e in order to obtain the orientation of the photoelectric transducer which depends upon the twisting of the rotation meter more specifically the orientation of the reference position e of sonde 14 can be obtained by adding the angle of rotation u03b4 measure by the rotation meter 9 to the azimuth angle u03b8 measured by the azimuth finder.