114 - 



As an experiment, the divers' compasses were placed on an arm 

 above the end of the steel channel that holds the arm. The compass 

 was then slid towards the end of the arm. The heading changed as the 

 compass was slid across the end of the steel channel and then 

 remained relatively stable. It was therefore thought at the time 

 that the readings taken at the ends of the PVC arms were sufficiently 

 far from the steel cradle to avoid any bias of the divers' compasses. 

 However, as can be seen from Table 6.1, this was not true. Since 

 each arm is perpendicular to its neighboring arm, each of the compass 

 readings are restrained to be 90 degrees apart. Although the digital 

 compass measurements approximate 90 degree separation, those of the 

 wrist compasses clearly do not. 



TABLE 6-1: ORIENTATION HEADINGS OF THE DPG ARm 





WRIST COMPASS 



DIGITAL 



COMPASS 



RESOLVED 



AnM 



apparent 



actual 



apparent 



actual 



average 



1 



228.33 



241.75 



238. 80 



241.89 



241.82 



2 



155.33 



151.75 



153.90 



151.89 



151.82 



3 



78.00 



61.75 



61.20 



61.89 



61.82 



4 



325.33 



331.75 



333.65 



331.89 



331.82 



Headings are with respect to magnetic north, 6/15/82. 



