*-- Author :  R. Henderson
      SUBROUTINE FPPPTZ(PERSEG,Z)
C                                                                                                             
C---  Propagates planars error matrix from z=0 to z=z                                                         
C                                                                                                             
C---                                                                                                          
C                                                                                                             
C---  Construct the derivative matrix                                                                         
C                                                                                                             
      CALL VZERO(DERIV,16)                                                                             
C                                                                                                             
C---  Propagate PERSEG FROM Z=0 TO Z                                                                          
C                                                                                                             
      CALL VZERO(WM,16)                                                                                
C                                                                                                             
C---                                                                                                          
      CALL VZERO(COVAR,32)                                                                             
C---                                                                                                          
      CALL UCOPY(COVAR,PERSEG,32)                                                                      
C---                                                                                                          
*