anchor.diff:  
   C----------------------------------------------------------------------C
   C                                                                       
  -C        SUBROUTINE PNPOLY                                              
  +C        SUBROUTINE pnpoly                                              
   C                                                                       
   C        PURPOSE                                                        
   C           TO DETERMINE WHETHER A POINT IS INSIDE A POLYGON            
  
positive.code:       CHARACTER*40 ofile
        CHARACTER*200 clip
        REAL*8 x1,x2,y1,y2,dx,dy,dz,dd,ref(5),dist,az,lo,la
        REAL*8 x,y,z,xx(1000),yy(1000),zsave
        INTEGER i,j,nx,ny,p,xsec,xz,nn,io
  
  C----
  C Get parameters from the command line
  C----
        call gcmdln(x1,x2,nx,dx,y1,y2,ny,dy,z,ofile,p,ref,xsec,xz,clip)
  C Check that limits and increments are properly defined
  
negative.code: C                                                                       
  C     ..................................................................
  C                                                                       
        SUBROUTINE pnpoly(PX,PY,XX,YY,N,INOUT)
        IMPLICIT NONE
        INTEGER MAXDIM
        PARAMETER (MAXDIM=1000)
        REAL*8 X(MAXDIM),Y(MAXDIM),XX(N),YY(N),PX,PY,var
        INTEGER N,INOUT,I,J
        LOGICAL MX,MY,NX,NY
  
  C Check that number of points in clipping path is less than MAXDIM
        IF (N.GT.MAXDIM) THEN
            WRITE(0,7) N
  7         FORMAT('WARNING:',I5,' TOO GREAT FOR THIS VERSION OF PNPOLY')
            RETURN
        ENDIF
  
  C Compute the position of the points on the clipping path (xx,yy)
  C relative to the point of interest (px,py)
        DO 1 I=1,N
            X(I)=XX(I)-PX
            Y(I)=YY(I)-PY
  