*-- Author : S.Burke / J.V. Morris
      SUBROUTINE FKCOVP(CPRO,H,GMES,CFIL,WT,IERR)
**********************************************************************                                        
*                                                                    *                                        
* Calculate filtered covariance for a `planar' (i.e. only one        *                                        
* measurement)                                                       *                                        
*                                                                    *                                        
* ERROR CONDITIONS;                                                  *                                        
*       IERR =   0 ; normal termination                              *                                        
*   ->  IERR = 111 ; filtered covariance not positive definite       *                                        
*                                                                    *                                        
*   ->  Fatal error                                                  *                                        
*                                                                    *                                        
**********************************************************************                                        
*KEEP,FKECODE.                                                                                                
*KEND.                                                                                                        
**********************************************************************                                        
* Rotate the top left corner of CPRO into measurement space ...                                               
* Premultiply by GMES, add  the unit matrix and invert - all trivial ...                                      
         CALL FKERR(IUTIL,IROUT,IFATAL,IOCV,IERR)
* ... except for rotating the result back into state vector space ...                                         
* ... and finally, premultiply by CPRO                                                                        
* For 1/3 of the planars there is no rotation, and the rest is trivial                                        
         CALL FKERR(IUTIL,IROUT,IFATAL,IOCV,IERR)
*                                                                                                             
* Same as the above, for a different wire alignment (I think this                                             
* is the one which actually occurs).                                                                          
*                                                                                                             
         CALL FKERR(IUTIL,IROUT,IFATAL,IOCV,IERR)
* ... and finally, premultiply by CPRO                                                                        
*