last computed position of the detector: 

 CABLE (YV n - YD n _ x ) 



YD n = YV r 



XD n = XV n 



/(YV n - YD^) 2 + (XV n - XD n _ ± )- 



CABLE XV n - XD n _-L) 



) n _ 1 )2 + (XV n - XD^-l)' 



where XD and YD are the coordinates of the detector and XV and YV are the 

 coordinates of the vessel. "CABLE" is the horizontal distance the detector 

 lies astern of the survey vessel. 



Also printed on the third map type is the centroid of_the_ detected 

 radioactive material, which is located "by the coordinates X, Y, where: 



n 



Y X. CC. 



ii-i x x 



X = 



Y = 



1=1 C °: 



I Y i CC i 

 i=l 

 n 



I CCi 

 i=l 



Xj_ and Y^ are the coordinates of each fix in the survey; CCi 1S "t ne 

 corrected radiation count at each fix and n is the number of fixes. 



25 



