*-- Author :    R. Henderson   24/10/94
      SUBROUTINE FPNDCA(TODIG,VDIG,TOCLS,VCLS,DIST)
C------------------------------------------------------------                                                 
C-----  FIND dca for the vectors a = todig + x*vdig                                                           
C-----           and the vectors b = tocls + x*vcls                                                           
C------------------------------------------------------------                                                 
                                                                        
      DOUBLE PRECISION AX(3,3),BTRIX(3),ADET,A1,A2,A3                   
      DIMENSION TODIG(3),VDIG(3),TOCLS(3),VCLS(3),TCP(3)                
                                                                        
C------------------------------------------------------------                                                 
                                                                        
      TCP(1) = VCLS(2)*VDIG(3) - VCLS(3)*VDIG(2)                        
      TCP(2) = VCLS(3)*VDIG(1) - VCLS(1)*VDIG(3)                        
      TCP(3) = VCLS(1)*VDIG(2) - VCLS(2)*VDIG(1)                        
                                                                        
      AX(1,1) = VCLS(1)                                                 
      AX(1,2) = VCLS(2)                                                 
      AX(1,3) = VCLS(3)                                                 
      AX(2,1) = -VDIG(1)                                                
      AX(2,2) = -VDIG(2)                                                
      AX(2,3) = -VDIG(3)                                                
      AX(3,1) = TCP(1)                                                  
      AX(3,2) = TCP(2)                                                  
      AX(3,3) = TCP(3)                                                  
                                                                        
      ADET = AX(1,3)*(AX(2,2)*AX(3,1) - AX(2,1)*AX(3,2))                
     &     - AX(2,3)*(AX(1,2)*AX(3,1) - AX(1,1)*AX(3,2))                
     &     + AX(3,3)*(AX(1,2)*AX(2,1) - AX(2,2)*AX(1,1))                
                                                                        
      A1 = AX(1,3)*AX(2,2) - AX(1,2)*AX(2,3)                            
      A2 = AX(1,1)*AX(2,3) - AX(1,3)*AX(2,1)                            
      A3 = AX(1,2)*AX(2,1) - AX(1,1)*AX(2,2)                            
                                                                        
      BTRIX(1) = TOCLS(1) - TODIG(1)                                    
      BTRIX(2) = TOCLS(2) - TODIG(2)                                    
      BTRIX(3) = TOCLS(3) - TODIG(3)                                    
                                                                        
      VMOD = TCP(1)**2 + TCP(2)**2 + TCP(3)**2                          
                                                                        
      DIST = (A1*BTRIX(1) + A2*BTRIX(2) + A3*BTRIX(3))*SQRT(VMOD)/ADET  
                                                                        
      RETURN                                                            
      END                                                               
*